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Why You Should Choose HTML5 <article> Over <section>

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Why You Should Choose HTML5 <article> Over <section>

Why You Should Choose HTML5 <article> Over <section>

Bruce Lawson



A few days ago, I was having a chat with some friends, one of whom asked me the difference between <article> and <section> in HTML. This is one of the eternal mysteries of web development, up there with “why is it white-space: nowrap, not white-space: no-wrap?” and “why is CSS ‘gray’ a darker color than ‘darkgray’?”.

I gave my usual answer: think of <article> not just as a newspaper article, or a blog post, but as an article of clothing — a discrete entity that can be reused in another context. So your trousers are an article, and you can wear them with a different outfit; your shirt is an article, and can be worn with different trousers; your knee-length patent leather stiletto boots are an article (you wouldn’t wear just one of them, would you?).

The spec says:

“The article element represents a complete, or self-contained, composition in a document, page, application, or site and that is, in principle, independently distributable or reusable, e.g. in syndication. This could be a forum post, a magazine or newspaper article, a blog entry, a user-submitted comment, an interactive widget or gadget, or any other independent item of content.”

So a homepage with a list of blog posts would be a <main> element wrapping a series of <article> elements, one for each blog post. You would use the same structure for a list of videos (think YouTube) with each video being wrapped in an <article>, a list of products (think Amazon) and so on. Any of those <article>s is conceptually syndicatable — each could stand alone on its own dedicated page, in an advert on another page, as an entry in an RSS feed, and so on.

Apple’s WatchOS contains Reader which uses the <article> element to know the primary content of your page. Apple says:

“We’ve brought Reader to watchOS 5 where it automatically activates when following links to text-heavy web pages. It’s important to ensure that Reader draws out the key parts of your web page by using semantic markup to reinforce the meaning and purpose of elements in the document. Let’s walk through an example. First, we indicate which parts of the page are the most important by wrapping it in an article tag.”

Combining <article> with HTML5 microdata helps Reader construct the optimal display for small watch screens:

“Specifically, enclosing these header elements inside the article ensure that they all appear in Reader. Reader also styles each header element differently depending on the value of its itemprop attribute. Using itemprop, we’re able to ensure that the author, publication date, title, and subheading are prominently featured.”

So What About <section>?

My usual advice continues: don’t bother with <section> or worry about how it differs from <article>. It was invented as a generic wrapper for headings so that the browser could determine the HTML5 document outline.

The what? The document outline algorithm is a way to use only one heading tag — <h1> — and have it magically “become” the correct level of heading (e.g. turn into an <h2>, <h3>, etc.), depending on how deeply it’s nested in HTML5 sectioning elements:<article>, <section>, and so on.

So, for example, here’s what you’ve typed into your CMS:

<h1>My Fabulous article</h1>

<p>Lorem Ipsum Trondant Fnord</p>

This works brilliantly when shown as a standalone article. But what about on your homepage, which is a list of your latest articles?

<h1>My latest posts</p>

<article>

  <h1>My fabulous article</h1>

 <p>Lorem Ipsum Trondant Fnord</p>

</article>

<article>

  <h1>Another magnum opus</h1>

  <p>Magnum solero paddlepop</p>

</article>

In this example, according to the specification, the <h1>s inside the <article> elements “become” logical <h2>s, because <article>, like <section>, is a sectioning element.

Note: This isn’t a new idea. Way back in 1991, Sir Uncle Timbo wrote:

“I would in fact prefer, instead of <h1>, <h2>, etc. for headings [those come from the AAP DTD] to have a nestable <SECTION></SECTION> element, and a generic <H></H> which at any level within the sections would produce the required level of Heading.”

Unfortunately, however, no browser implements HTML5 outlining, so there is no point in using <section>. At one point, the JAWS screen reader attempted to implement the document outlining algorithm (in IE, but not on Firefox) but implemented it buggily. It seems that browser developers simply aren’t interested (more sordid details in the Further Reading section for true anoraks).

“But,” interjected another friend in the conversation, “now browsers display different sizes of font depending on how deeply the <h1> is nested in <section>s”, and proceeded to prove it. Mind blown!

Here’s a similar demo. The left column shows four <h1>s, nested in sections; the right column shows a, <h1>, <h2>, <h3>, <h4> with no nesting. The Firefox screenshot shows that the nested <h1>s default to the same font as the traditional <h1><h4> tags:

Screenshot showing that the nested h1 elements, and the real heading elements display in the same sizes

A comparison of <h1>s nested in <section> elements and <h1>, <h2>, <h3>, <h4> (Large preview)

The results are the same in Chrome, Chromium derivatives such as Edge beta for Mac, and Safari on Mac.

So does this mean that we should all happily start using <h1> as our only heading element, nesting it in <section>s?

No. Because this is only a change in the visual styling of the h1s. If we crack open the Firefox Accessibility inspector in devtools, we can see that the text “level 2” is styled to look like an H2, but is still set at “level 1” — the Accessibility Tree hasn’t been changed to be level 2.

Screenshot of the firefox accessibility inspector selecting a nested h1 element

Firefox’s Accessibility Inspector shows that a nested <h1> appears visually the same as an <h2> but its aria-level is incorrectly set to “1”, not “2” (Large preview)

Compare this with the Real H2 in the right column:

Screenshot of the firefox accessibility inspector selecting a real h2 element

Firefox’s Accessibility Inspector shows that a real <h2> has a computed aria-level of “2”, which is correct (Large preview)

This shows the accessibility tree has been correctly informed that this is a level 2 heading. In fact, Mozilla did try communicating the computed level to the accessibility tree:

“We experimented a bit with that… but had to revert it because people in our a11y team complained about too many regressions (accidentally lowering <h1> levels and such).”

For assistive technology users, a proper hierarchy of headings is vital. As the eighth WebAIM screenreader user survey shows,

“The usefulness of proper heading structures is very high, with 86.1% of respondents finding heading levels very or somewhat useful.”

Therefore, you should continue to use <h1> until <h6>, and ignore section.

Never Say Never

“But..” you might now be spluttering indignantly, “there’s a <section> element right on this very page!”. And you would be right, dear reader. The “quick summary” is wrapped in a <section>, for accessibility reasons. When screen reader user Léonie Watson gave her webinar “How A Screen Reader User Accesses The Web”, she pointed out an area where Smashing Magazine’s markup could be tweaked to make her experience better.

As you can see from the screenshot, Smashing articles are preceded by a quick summary, followed by a horizontal line separating the summary from the article proper.

Screenshot of the top of a Smashing Magazine article

The Smashing “Quick Summary” is separated from its full article by a horizontal line. (Large preview)

But the separator is purely decorative, so Léonie couldn’t tell where the summary ends and the article begins. She suggested a fix: we wrapped the summary in a <section> element:

<section aria-label="quick summary">

    Summary text

</section>

In most screen readers, a <section> element isn’t announced unless it has an accessible name. In this case, the text of the aria label. Now, her screen reader announced “Quick summary region”, and after the summary “Quick summary region end”. This simple markup also makes it possible for a screen reader user to jump over the summary if they want to.

We could have used a simple <div> but then, as Marco Zehe writes,

“As a rule of thumb, if you label something via aria-label or aria-labelledby, make sure it has a proper widget or landmark role.”

So rather than use <div role=”region” aria-label=”quick summary”>, we chose <section> as that has a built-in role of region and Bruce’s infallible law of ARIA™ applies: built-in beats bolt-on. Bigly.

Conclusion

Hopefully, you’ve come away with these take-homes:

  • Don’t use loads of <h1>s. Make <h1> the main heading of your page, then use <h2>, <h3>, <h4>, etc. in a proper hierarchy without skipping levels.
  • <section> can be used with aria-label to signal to a screen reader user where a particular sub-part of an article begins and ends. Otherwise, forget about it, or use another element, such as <aside aria-label=”quick summary”> or <div role=”region” aria-label=”quick summary”>.
  • <main>, <header>, <footer> and <nav> are very useful for screen reader users, and entirely transparent to those who don’t use assistive technology. So use them.
  • <article> isn’t just for blog posts — it’s for any self-contained thing. It also helps WatchOS display your content properly.

I gratefully acknowledge Léonie Watson’s help writing this article. Any errors are totally her fault.

Further Reading

  • Headings And Sections,” HTML 5.2
    W3C Recommendation
    (14 Dec. ’17)
    Note its warning: “There are currently no known native implementations of the outline algorithm … Therefore the outline algorithm cannot be relied upon to convey document structure to users. Authors should use heading rank (h1-h6) to convey document structure.”
  • There Is No Document Outline Algorithm,” Adrian Roselli
    All the gory details of how the specification for the sectioning algorithm has changed.
  • ARIA in HTML,” W3C Editor’s Draft (19 Dec. ’19)
    Rules to live by if you do find yourself adding ARIA roles and attributes to HTML.
  • The Practical Value Of Semantic HTML,” Bruce Lawson
    My own article, linking to details of how WatchOS uses HTML5 and microdata.
Smashing Editorial
(ra, il)

Source: Smashing Magazine, Why You Should Choose HTML5 &lt;article&gt; Over &lt;section&gt;

Front-End Performance Checklist 2020 [PDF, Apple Pages, MS Word]

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Front-End Performance Checklist 2020 [PDF, Apple Pages, MS Word]

Front-End Performance Checklist 2020 [PDF, Apple Pages, MS Word]

Vitaly Friedman



Web performance is a tricky beast, isn’t it? How do we actually know where we stand in terms of performance, and what our performance bottlenecks exactly are? Is it expensive JavaScript, slow web font delivery, heavy images, or sluggish rendering? Is it worth exploring tree-shaking, scope hoisting, code-splitting, and all the fancy loading patterns with intersection observer, server push, clients hints, HTTP/2, service workers and — oh my — edge workers? And, most importantly, where do we even start improving performance and how do we establish a performance culture long-term?

Back in the day, performance was often a mere afterthought. Often deferred till the very end of the project, it would boil down to minification, concatenation, asset optimization and potentially a few fine adjustments on the server’s config file. Looking back now, things seem to have changed quite significantly.

Performance isn’t just a technical concern: it affects everything from accessibility to usability to search engine optimization, and when baking it into the workflow, design decisions have to be informed by their performance implications. Performance has to be measured, monitored and refined continually, and the growing complexity of the web poses new challenges that make it hard to keep track of metrics, because metrics will vary significantly depending on the device, browser, protocol, network type and latency (CDNs, ISPs, caches, proxies, firewalls, load balancers and servers all play a role in performance).

So, if we created an overview of all the things we have to keep in mind when improving performance — from the very start of the process until the final release of the website — what would that list look like? Below you’ll find a (hopefully unbiased and objective) front-end performance checklist for 2020 — an updated overview of the issues you might need to consider to ensure that your response times are fast, user interaction is smooth and your sites don’t drain user’s bandwidth.

Table Of Contents

(You can also just download the checklist PDF (166 KB) or download editable Apple Pages file (275 KB) or the .docx file (151 KB). Happy optimizing, everyone!)

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list-style: none;
margin-bottom: 1.5em;
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font-family: “Mija”, Arial, sans-serif;
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Getting Ready: Planning And Metrics

Micro-optimizations are great for keeping performance on track, but it’s critical to have clearly defined targets in mind — measurable goals that would influence any decisions made throughout the process. There are a couple of different models, and the ones discussed below are quite opinionated — just make sure to set your own priorities early on.

  1. Establish a performance culture.
    In many organizations, front-end developers know exactly what common underlying problems are and what loading patterns should be used to fix them. However, as long as there is no established endorsement of the performance culture, each decision will turn into a battlefield of departments, breaking up the organization into silos. You need a business stakeholder buy-in, and to get it, you need to establish a case study, or a proof of concept using the Performance API on how speed benefits metrics and Key Performance Indicators (KPIs) they care about.

    Without a strong alignment between dev/design and business/marketing teams, performance isn’t going to sustain long-term. Study common complaints coming into customer service and sales team, study analytics for high bounce rates and conversion drops. Explore how improving performance can help relieve some of these common problems. Adjust the argument depending on the group of stakeholders you are speaking to.

    Run performance experiments and measure outcomes — both on mobile and on desktop (for example, with Google Analytics). It will help you build up a company-tailored case study with real data. Furthermore, using data from case studies and experiments published on WPO Stats will help increase sensitivity for business about why performance matters, and what impact it has on user experience and business metrics. Stating that performance matters alone isn’t enough though — you also need to establish some measurable and trackable goals and observe them over time.

    How to get there? In her talk on Building Performance for the Long Term, Allison McKnight shares a comprehensive case-study of how she helped establish a performance culture at Etsy (slides). More recently, Tammy Averts has spoken about habits of highly effective performance teams in both small and large organizations.

Brad Frost and Jonathan Fielding’s Performance Budget Calculator

Performance budget builder by Brad Frost and Jonathan Fielding’s Performance Budget Calculator can help you set up your performance budget and visualize it. (Large preview)
  1. Goal: Be at least 20% faster than your fastest competitor.
    According to psychological research, if you want users to feel that your website is faster than your competitor’s website, you need to be at least 20% faster. Study your main competitors, collect metrics on how they perform on mobile and desktop and set thresholds that would help you outpace them. To get accurate results and goals though, make sure to first get a thorough picture of your users’ experience by studying your analytics. You can then mimic the 90th percentile’s experience for testing.

    To get a good first impression of how your competitors perform, you can use Chrome UX Report (CrUX, a ready-made RUM data set, video introduction by Ilya Grigorik and detailed guide by Rick Viscomi) or Treo Sites, a RUM monitoring tool that is powered by Chrome UX Report. Alternatively, you can also use Speed Scorecard (also provides a revenue impact estimator), Real User Experience Test Comparison or SiteSpeed CI (based on synthetic testing).

    Treo Sites provides competitive analysis based on real-world data

    Treo Sites provides competitive analysis based on real-world data. (Large preview)

    Note: If you use Page Speed Insights (no, it isn’t deprecated), you can get CrUX performance data for specific pages instead of just the aggregates. This data can be much more useful for setting performance targets for assets like “landing page” or “product listing”. And if you are using CI to test the budgets, you need to make sure your tested environment matches CrUX if you used CrUX for setting the target (thanks Patrick Meenan!).

    If you need some help to show the reasoning behind prioritization of speed, or you’d like to visualize conversion rate decay or increase in bounce rate with slower performance, or perhaps you’d need to advocate for a RUM solution in your organization, Sergey Chernyshev has built a UX Speed Calculator, an open-source tool that helps you simulate data and visualize it to drive your point across.

    Just when you need to make a case for performance to drive your point across: UX Speed Calculator visualizes an impact of performanc on bounce rates, conversion and total revenue, based on real data

    Just when you need to make a case for performance to drive your point across: UX Speed Calculator visualizes an impact of performanc on bounce rates, conversion and total revenue — based on real data. (Large preview)

    Collect data, set up a spreadsheet, shave off 20%, and set up your goals (performance budgets) this way. Now you have something measurable to test against. If you’re keeping the budget in mind and trying to ship down just the minimal payload to get a quick time-to-interactive, then you’re on a reasonable path.

    Need resources to get started?

    Once you have a budget in place, incorporate them into your build process with Webpack Performance Hints and Bundlesize, Lighthouse CI, PWMetrics or Sitespeed CI to enforce budgets on pull requests and provide a score history in PR comments.

    To expose performance budgets to the entire team, integrate performance budgets in Lighthouse via Lightwallet. And if you need something custom, you can use webpagetest-charts-api, an API of endpoints to build charts from WebPagetest results.

    Performance awareness shouldn’t come from performance budgets alone though. Just like Pinterest, you could create a custom eslint rule that disallows importing from files and directories that are known to be dependency-heavy and would bloat the bundle. Set up a listing of “safe” packages that can be shared across the entire team.

    Also, think about critical customer tasks that are most beneficial to your business. Study, discuss and define acceptable time thresholds for critical actions and establish “UX ready” user timing marks that the entire organization has approved. In many cases, user journeys will touch on the work of many different departments, so alignment in terms of acceptable timings will help support or prevent performance discussions down the road. Make sure that additional costs of added resources and features are visible and understood.

    Align performance efforts with other tech initiatives, ranging from new features of the product being built to refactoring to reaching to new global audiences. So every time a conversation about further development happens, performance is a part of that conversation as well. It’s much easier to reach performance goals when the code base is fresh or is just being refactored. Once you’ve established a strong performance culture in your organization, aim for being 20% faster than your former self to keep priorities in tact as time passes by. (thanks, Guy Podjarny!)

    Also, as Patrick Meenan suggested, it’s worth to plan out a loading sequence and trade-offs during the design process. If you prioritize early on which parts are more critical, and define the order in which they should appear, you will also know what can be delayed. Ideally, that order will also reflect the sequence of your CSS and JavaScript imports, so handling them during the build process will be easier. Also, consider what the visual experience should be in “in-between”-states, while the page is being loaded (e.g. when web fonts aren’t loaded yet).

    Planning, planning, planning. It might be tempting to get into quick “low-hanging-fruits”-optimizations early on — and it might be a good strategy for quick wins — but it will be very hard to keep performance a priority without planning and setting realistic, company-tailored performance goals.

The difference between First Paint, First Contentful Paint, First Meaningful Paint, Visual Complete and Time To Interactive. Large view. Credit: @denar90

New metrics landing in Lighthouse v6 in early 2020. First Meaningful Paint (FMP) is now deprecated, and Largest Contentful Paint (LCP) and Total Blocking Time (TBT) are coming in Lighthouse soon

New metrics landing in Lighthouse v6 in early 2020. First Meaningful Paint (FMP) is now deprecated, and Largest Contentful Paint (LCP) and Total Blocking Time (TBT) are coming in Lighthouse soon. (Large preview)
  1. Choose the right metrics.
    Not all metrics are equally important. Study what metrics matter most to your application: usually, it will be defined by how fast you can start to render most important pixels of your interface and how quickly you can provide input responsiveness for these rendered pixels. This knowledge will give you the best optimization target for ongoing efforts. In the end, it’s not the load events or server response times that define the experience, but the perception of how snappy the interface feels.

    What does it mean? Rather than focusing on full page loading time (via onLoad and DOMContentLoaded timings, for example), prioritize page loading as perceived by your customers. That means focusing on a slightly different set of metrics. In fact, choosing the right metric is a process without obvious winners.

    Based on Tim Kadlec’s research and Marcos Iglesias’ notes in his talk, traditional metrics could be grouped into a few sets. Usually, we’ll need all of them to get a complete picture of performance, and in your particular case some of them might be more important than others.

    • Quantity-based metrics measure the number of requests, weight and a performance score. Good for raising alarms and monitoring changes over time, not so good for understanding user experience.
    • Milestone metrics use states in the lifetime of the loading process, e.g. Time To First Byte and Time To Interactive. Good for describing the user experience and monitoring, not so good for knowing what happens between the milestones.
    • Rendering metrics provide an estimate of how fast content renders (e.g. Start Render time, Speed Index). Good for measuring and tweaking rendering performance, but not so good for measuring when important content appears and can be interacted with.
    • Custom metrics measure a particular, custom event for the user, e.g. Twitter’s Time To First Tweet and Pinterest’s PinnerWaitTime. Good for describing the user experience precisely, not so good for scaling the metrics and comparing with with competitors.

    To complete the picture, we’d usually look out for useful metrics among all of these groups. Usually, the most specific and relevant ones are:

    • Time to Interactive (TTI)
      The point at which layout has stabilized, key webfonts are visible, and the main thread is available enough to handle user input — basically the time mark when a user can interact with the UI. The key metrics for understanding how much wait a user has to experience to use the site without a lag.
    • First Input Delay (FID), or Input responsiveness
      The time from when a user first interacts with your site to the time when the browser is actually able to respond to that interaction. Complements TTI very well as it describes the missing part of the picture: what happens when a user actually interacts with the site. Intended as a RUM metric only. There is a JavaScript library for measuring FID in the browser.
    • Largest Contentful Paint (LCP)
      Marks the point in the page load timeline when the page’s important content has likely loaded. The assumption is that the most important element of the page is the largest one visible in the user’s viewport. If elements are rendered both above and below the fold, only the visible part is considered relevant. Currently a hidden metric in Lighthouse, to be rolled out if it proves to be valuable.
    • Total Blocking Time (TBT)
      A new metric that helps quantify the severity of how non-interactive a page is prior to it becoming reliably interactive (that is, the main thread has been free of any tasks running over 50ms (long tasks) for at least 5s). The metric measures the total amount of time between the first paint and Time to Interactive (TTI) where the main thread was blocked for long enough to prevent input responsiveness. No wonder, then, that a low TBT is a good indicator for good performance. (thanks, Artem, Phil)
    • Cumulative Layout Shift (CLS)
      The metric highlights how often users experience unexpected layout shifts (reflows) when accessing the site. It examines unstable elements and their impact on the overall experience. The lower the score, the better.
    • Speed Index
      Measures how quickly the page contents are visually populated; the lower the score, the better. The Speed Index score is computed based on the speed of visual progress, but it’s merely a computed value. It’s also sensitive to the viewport size, so you need to define a range of testing configurations that match your target audience. Note that it is becoming less important with LCP coming in as a new metric (thanks, Boris, Artem!).
    • CPU time spent
      A metric that shows how often and how long the main thread is blocked, working on painting, rendering, scripting and loading. High CPU time is a clear indicator of a janky experience, i.e. when the user experiences a noticeable lag between their action and a response. With WebPageTest, you can select “Capture Dev Tools Timeline” on the “Chrome” tab to expose the breakdown of the main thread as it runs on any device using WebPageTest.
    • Component-Level CPU Costs
      Just like with the CPU time spent, this metric, proposed by Stoyan Stefanov, explores the impact of JavaScript on CPU. The idea is to use CPU instruction count per component to understand its impact on the overall experience, in isolation. Could be implemented using Puppeteer and Chrome.
    • FrustrationIndex
      While many metrics featured above explain when a particular event happens, Tim Vereecke’s FrustrationIndex looks at the gaps between metrics instead of looking at them individually. It looks at the key milestones perceived by the end-user, such as Title is visible, First content is visible, Visually ready and Page looks ready and calculates a score indicating the level of frustration while loading a page. The bigger the gap, the bigger the chance a user gets frustrated. Potentially a good KPI for user experience. Tim has published a detailed post about FrustrationIndex and how it works.
    • Ad Weight Impact
      If your site depends on the revenue generated by advertising, it’s useful to track the weight of ad related code. Paddy Ganti’s script constructs two URLs (one normal and one blocking the ads), prompts the generation of a video comparison via WebPageTest and reports a delta.
    • Deviation metrics
      As noted by Wikipedia engineers, data of how much variance exists in your results could inform you how reliable your instruments are, and how much attention you should pay to deviations and outlers. Large variance is an indicator of adjustments needed in the setup. It also helps understand if certain pages are more difficult to measure reliably, e.g. due to third-party scripts causing significant variation. It might also be a good idea to track browser version to understand bumps in performance when a new browser version is rolled out.
    • Custom metrics
      Custom metrics are defined by your business needs and customer experience. It requires you to identify important pixels, critical scripts, necessary CSS and relevant assets and measure how quickly they get delivered to the user. For that one, you can monitor Hero Rendering Times, or use Performance API, marking particular timestamps for events that are important for your business. Also, you can collect custom metrics with WebPagetest by executing arbitrary JavaScript at the end of a test.

    Note that the First Meaningful Paint (FMP) doesn’t appear in the overview above. It used to provide an insight into how quickly the server outputs any data. Long FMP usually indicated JavaScript blocking the main thread, but could be related to back-end/server issues as well. However, the metric has been deprecated recently as it appears not to be accurate in about 20% of the cases. It will no longer be supported in the next versions of Lighthouse.

    Steve Souders has a detailed explanation of most of these metrics. It’s important to notice that while Time-To-Interactive is measured by running automated audits in the so-called lab environment, First Input Delay represents the actual user experience, with actual users experiencing a noticeable lag. In general, it’s probably a good idea to always measure and track both of them.

    Depending on the context of your application, preferred metrics might differ: e.g. for Netflix TV UI, key input responsiveness, memory usage and TTI are more critical, and for Wikipedia, first/last visual changes and CPU time spent metrics are more important.

    Note: both FID and TTI do not account for scrolling behavior; scrolling can happen independently since it’s off-main-thread, so for many content consumption sites these metrics might be much less important (thanks, Patrick!).

User-centric performance metrics provide a better insight into the actual user experience. First Input Delay (FID) is a new metric that tries to achieve just that. (Large preview)
  1. Gather data on a device representative of your audience.
    To gather accurate data, we need to thoroughly choose devices to test on. In most companies, that means looking into analytics and creating user profiles based on most common device types. Yet often, analytics alone doesn’t provide a complete picture. A significant portion of the target audience might be abandoning the site (and not returning back) just because their experience is too slow, and their devices are unlikely to show up as the most popular devices in analytics. So additionally conducting research on common devices in your target group might be a good idea.

    Globally in 2018–2019, according to the IDC, 87% of all shipped mobile phones are Android devices. An average consumer upgrades their phone every 2 years, and in the US phone replacement cycle is 33 months. Average bestselling phones around the world will cost under $200.

    A representative device, then, is an Android device that is at least 24 months old, costing $200 or less, running on slow 3G, 400ms RTT and 400kbps transfer, just to be slightly more pessimistic. This might be very different for your company, of course, but that’s a close enough approximation of a majority of customers out there. In fact, it might be a good idea to look into current Amazon Best Sellers for your target market. (Thanks to Tim Kadlec, Henri Helvetica and Alex Russel for the pointers!).

    What test devices to choose then? The ones that fit well with the profile outlined above. It’s a good option to choose a Moto G4/G5 Plus, a mid-range Samsung device (Galaxy A50, S8), a good middle-of-the-road device like a Nexus 5X, Xiaomi Mi A3 or Xiaomi Redmi Note 7 and a slow device like Alcatel 1X or Cubot X19, perhaps in an open device lab. For testing on slower thermal-throttled devices, you could also get a Nexus 4, which costs just around $100.

    Also, check the chipsets used in each device and do not over-represent one chipset: a few generations of Snapdragon and Apple as well as low-end Rockchip, Mediatek would be enough (thanks, Patrick!).

    If you don’t have a device at hand, emulate mobile experience on desktop by testing on a throttled 3G network (e.g. 300ms RTT, 1.6 Mbps down, 0.8 Mbps up) with a throttled CPU (5× slowdown). Eventually switch over to regular 3G, slow 4G (e.g. 170ms RTT, 9 Mbps down, 9Mbps up), and Wi-Fi. To make the performance impact more visible, you could even introduce 2G Tuesdays or set up a throttled 3G/4G network in your office for faster testing.

    Keep in mind that on a mobile device, we should be expecting a 4×–5× slowdown compared to desktop machines. Mobile devices have different GPUs, CPU, memory and different battery characteristics. That’s why it’s important to have a good profile of an average device and always test on an such a device.

  2. Introducing the slowest day of the week
    Introducing the slowest day of the week. Facebook has introduced 2G Tuesdays to increase visibility and sensitivity of slow connections. (Image source)

    Luckily, there are many great options that help you automate the collection of data and measure how your website performs over time according to these metrics. Keep in mind that a good performance picture covers a set of performance metrics, lab data and field data:

    • Synthetic testing tools collect lab data in a reproducible environment with predefined device and network settings (e.g. Lighthouse, Calibre, WebPageTest) and
    • Real User Monitoring (RUM) tools evaluate user interactions continuously and collect field data (e.g. SpeedCurve, New Relic — the tools provide synthetic testing, too).

    The former is particularly useful during development as it will help you identify, isolate and fix performance issues while working on the product. The latter is useful for long-term maintenance as it will help you understand your performance bottlenecks as they are happening live — when users actually access the site.

    By tapping into built-in RUM APIs such as Navigation Timing, Resource Timing, Paint Timing, Long Tasks, etc., synthetic testing tools and RUM together provide a complete picture of performance in your application. You could use PWMetrics, Calibre, SpeedCurve, mPulse and Boomerang, Sitespeed.io, which all are great options for performance monitoring. Furthermore, with Server Timing header, you could even
    monitor back-end and front-end performance all in one place.

    Note: It’s always a safer bet to choose network-level throttlers, external to the browser, as, for example, DevTools has issues interacting with HTTP/2 push, due to the way it’s implemented (thanks, Yoav, Patrick!). For Mac OS, we can use Network Link Conditioner, for Windows Windows Traffic Shaper, for Linux netem, and for FreeBSD dummynet.

Lighthouse

Lighthouse, a performance auditing tool integrated into DevTools. (Large preview)
  1. Set up “clean” and “customer” profiles for testing.
    While running tests in passive monitoring tools, it’s a common strategy to turn off anti-virus and background CPU tasks, remove background bandwidth transfers and test with a clean user profile without browser extensions to avoid skewed results (Firefox, Chrome).

    However, it’s also a good idea to study which extensions your customers are using frequently, and test with a dedicated “customer” profile as well. In fact, some extensions might have a profound performance impact (study) on your application, and if your users use them a lot, you might want to account for it up front. “Clean” profile results alone are overly optimistic and can be crushed in real-life scenarios.

  2. Share the performance goals with your colleagues.
    Make sure that performance goals are familiar to every member of your team to avoid misunderstandings down the line. Every decision — be it design, marketing or anything in-between — has performance implications, and distributing responsibility and ownership across the entire team would streamline performance-focused decisions later on. Map design decisions against performance budget and the priorities defined early on.

Setting Realistic Goals

  1. 100-millisecond response time, 60 fps.
    For an interaction to feel smooth, the interface has 100ms to respond to user’s input. Any longer than that, and the user perceives the app as laggy. The RAIL, a user-centered performance model gives you healthy targets: To allow for <100 milliseconds response, the page must yield control back to main thread at latest after every <50 milliseconds. Estimated Input Latency tells us if we are hitting that threshold, and ideally, it should be below 50ms. For high-pressure points like animation, it’s best to do nothing else where you can and the absolute minimum where you can’t.


    RAIL
    RAIL, a user-centric performance model.

    Also, each frame of animation should be completed in less than 16 milliseconds, thereby achieving 60 frames per second (1 second ÷ 60 = 16.6 milliseconds) — preferably under 10 milliseconds. Because the browser needs time to paint the new frame to the screen, your code should finish executing before hitting the 16.6 milliseconds mark. We’re starting to have conversations about 120fps (e.g. iPad Pro’s screens run at 120Hz) and Surma has covered some rendering performance solutions for 120fps, but that’s probably not a target we’re looking at just yet.

    Be pessimistic in performance expectations, but be optimistic in interface design and use idle time wisely (check idlize and idle-until-urgent). Obviously, these targets apply to runtime performance, rather than loading performance.

  2. FID < 100ms, TTI < 5s on 3G, Speed Index < 3s, Critical file size budget < 170KB (gzipped).
    Although it might be very difficult to achieve, a good ultimate goal would be Speed Index under 3s and Time to Interactive under 5s, and for repeat visits, aim for under 2s (achievable only with a service worker). Aim for Largest Contentful Paint of under 1s and minimize Total Blocking Time and Cumulative Layout Shift. An acceptable First Input Delay (highlighted as Max Potential First Input Delay in Lighthouse) is under 130–100ms. As mentioned above, we’re considering the baseline being a $200 Android phone (e.g. Moto G4) on a slow 3G network, emulated at 400ms RTT and 400kbps transfer speed.

    We have two major constraints that effectively shape a reasonable target for speedy delivery of the content on the web. On the one hand, we have network delivery constraints due to TCP Slow Start. The first 14KB of the HTML — 10 TCP packets, each 1460 bytes, making around 14.25 KB, albeit not to be taken literally — is the most critical payload chunk, and the only part of the budget that can be delivered in the first roundtrip (which is all you get in 1 sec at 400ms RTT due to mobile wake-up times).

    (Note: as TCP generally under-utilizes network connection by a significant amount, Google has developed TCP Bottleneck Bandwidth and RRT (BBR), a relatively new TCP delay-controlled TCP flow control algorithm. Designed for the modern web, it responds to actual congestion, rather than packet loss like TCP does, it is significantly faster, with higher throughput and lower latency — and the algorithm works differently. It’s still important to prioritize critical resources as early as possible, but 14 KB might not be that relevant with BBR in place.) (thanks, Victor, Barry!)

    On the other hand, we have hardware constraints on memory and CPU due to JavaScript parsing times (we’ll talk about them in detail later). To achieve the goals stated in the first paragraph, we have to consider the critical file size budget for JavaScript. Opinions vary on what that budget should be (and it heavily depends on the nature of your project), but a budget of 170KB JavaScript gzipped already would take up to 1s to parse and compile on an average phone. Assuming that 170KB expands to 3× that size when decompressed (0.7MB), that already could be the death knell of a “decent” user experience on a Moto G4/G5 Plus.

    If you want to target growing markets such as South East Asia, Africa or India, you’ll have to look into a very different set of constraints. Addy Osmani covers major feature phone constraints, such as few low cost, high-quality devices, unavailability of high-quality networks and expensive mobile data — along with PRPL-30 budget and development guidelines for these environments.

    According to Addy Osmani, a recommended size for lazy-loaded routes is also less than 35 KB

    According to Addy Osmani, a recommended size for lazy-loaded routes is also less than 35 KB. (Large preview)

    Addy Osmani suggests PRPL-30 performance budget (30KB gzipped + minified initial bundle) if targeting a feature phone

    Addy Osmani suggests PRPL-30 performance budget (30KB gzipped + minified initial bundle) if targeting a feature phone. (Large preview)

    In fact, Google’s Alex Russel recommends to aim for 130–170KB gzipped as a reasonable upper boundary. In real-life world, most products aren’t even close: an median bundle size today is around 417KB, which is up 42% compared to early 2015. On a middle-class mobile device, that accounts for 15–25 seconds for Time-To-Interactive.

    Geekbench CPU performance benchmarks for the highest selling smartphones globally in 2019. JavaScript stresses single-core performance and is CPU bound

    Geekbench CPU performance benchmarks for the highest selling smartphones globally in 2019. JavaScript stresses single-core performance (remember, it’s inherently more single-threaded than the rest of the Web Platform) and is CPU bound. From Addy’s article “Loading Web Pages Fast On A $20 Feature Phone”. (Large preview)

    We could also go beyond the bundle size budget though. For example, we could set performance budgets based on the activities of the browser’s main thread, i.e. paint time before start render, or track down front-end CPU hogs. Tools such as Calibre, SpeedCurve and Bundlesize can help you keep your budgets in check, and can be integrated into your build process.

    Finally, a performance budget probably shouldn’t be a fixed value. Depending on the network connection, performance budgets should adapt, but payload on slower connection is much more “expensive”, regardless of how they’re used.

    Note: It might sound strange to set such rigid budgets in times of wide-spread HTTP/2, upcoming 5G, rapidly evolving mobile phones and flourishing SPAs. However, they do sound reasonable when we deal with the unpredictable nature of the network and hardware, including everything from congested networks to slowly developing infrastructure, to data caps, proxy browsers, save-data mode and sneaky roaming charges.


From 'Fast By Default: Modern Loading Best Practices' by Addy Osmani
From Fast By Default: Modern loading best practices by Addy Osmani (Slide 19)

Performance budgets should adapt depending on the network conditions for an average mobile device. (Image source: Katie Hempenius) (Large preview)

Defining The Environment

  1. Choose and set up your build tools.
    Don’t pay too much attention to what’s supposedly cool these days. Stick to your environment for building, be it Grunt, Gulp, Webpack, Parcel, or a combination of tools. As long as you are getting results you need and you have no issues maintaining your build process, you’re doing just fine.

    Among the build tools, Rollup is gaining traction, but Webpack seems to be the most established one, with literally hundreds of plugins available to optimize the size of your builds. Getting started with Webpack can be tough though. So if you want to get started, there are some great resources out there:

  2. Use progressive enhancement as a default.
    Still, after all these years, keeping progressive enhancement as the guiding principle of your front-end architecture and deployment is a safe bet. Design and build the core experience first, and then enhance the experience with advanced features for capable browsers, creating resilient experiences. If your website runs fast on a slow machine with a poor screen in a poor browser on a sub-optimal network, then it will only run faster on a fast machine with a good browser on a decent network.

    In fact, with adaptive module serving, we seem to be taking progressive enhancement to another level, serving “lite” core experiences to low-end devices, and enhancing with more sophisticated features for high-end devices. Progressive enhancement isn’t likely to fade away any time soon, so it seems.

  3. <!–

    If you need a practical implementation of the strategy on mid-scale and large-scale projects, Scott Jehl’s Modernizing our Progressive Enhancement Delivery article is a good place to start.

    –>

  4. Choose a strong performance baseline.
    With so many unknowns impacting loading — the network, thermal throttling, cache eviction, third-party scripts, parser blocking patterns, disk I/O, IPC latency, installed extensions, antivirus software and firewalls, background CPU tasks, hardware and memory constraints, differences in L2/L3 caching, RTTS — JavaScript has the heaviest cost of the experience, next to web fonts blocking rendering by default and images often consuming too much memory. With the performance bottlenecks moving away from the server to the client, as developers, we have to consider all of these unknowns in much more detail.

    With a 170KB budget that already contains the critical-path HTML/CSS/JavaScript, router, state management, utilities, framework, and the application logic, we have to thoroughly examine network transfer cost, the parse/compile-time and the runtime cost of the framework of our choice. Luckily, we’ve seen a huge improvement over the last few years in how fast browsers can parse and compile scripts. Yet the execution of JavaScript is still the main bottleneck, so paying close attention to script execution time and network can be impactful.

    As noted by Seb Markbåge, a good way to measure start-up costs for frameworks is to first render a view, then delete it and then render again as it can tell you how the framework scales. The first render tends to warm up a bunch of lazily compiled code, which a larger tree can benefit from when it scales. The second render is basically an emulation of how code reuse on a page affects the performance characteristics as the page grows in complexity.

  5. Evaluate frameworks and dependencies.
    Now, not every project needs a framework and not every page of a single-page-application needs to load a framework. In Netflix’s case, “removing React, several libraries and the corresponding app code from the client-side reduced the total amount of JavaScript by over 200KB, causing an over-50% reduction in Netflix’s Time-to-Interactivity for the logged-out homepage.” The team then utilized the time spent by users on the landing page to prefetch React for subsequent pages that users were likely to land on (read on for details).

    It might sound obvious but worth stating: some projects can also benefit benefit from removing an existing framework altogether. Once a framework is chosen, you’ll be staying with it for at least a few years, so if you need to use one, make sure your choice is informed and well considered.

    Inian Parameshwaran has measured performance footprint of top 50 frameworks (against First Contentful Paint — the time from navigation to the time when the browser renders the first bit of content from the DOM). Inian discovered that, out there in the wild, Vue and Preact are the fastest across the board — both on desktop and mobile, followed by React (slides). You could examine your framework candidates and the proposed architecture, and study how most solutions out there perform, e.g. with server-side rendering or client-side rendering, on average.

    Baseline performance cost matters. According to a study by Ankur Sethi, “your React application will never load faster than about 1.1 seconds on an average phone in India, no matter how much you optimize it. Your Angular app will always take at least 2.7 seconds to boot up. The users of your Vue app will need to wait at least 1 second before they can start using it.” You might not be targeting India as your primary market anyway, but users accessing your site with suboptimal network conditions will have a comparable experience. In exchange, your team gains maintainability and developer efficiency, of course. But this consideration needs to be deliberate.

    You could go as far as evaluating a framework (or any JavaScript library) on Sacha Greif’s 12-point scale scoring system by exploring features, accessibility, stability, performance, package ecosystem, community, learning curve, documentation, tooling, track record, team, compatibility, security for example. But on a tough schedule, it’s a good idea to consider at least the total cost on size + initial parse times before choosing an option; lightweight options such as Preact, Inferno, Vue, Svelte or Polymer can get the job done just fine. The size of your baseline will define the constraints for your application’s code.

    There are many tools to help you make an informed decision about the impact of your dependencies and viable alternatives:

    A good starting point is to choose a good default stack for your application. Gatsby (React), Vuepress (Vue)Preact CLI, and PWA Starter Kit provide reasonable defaults for fast loading out of the box on average mobile hardware. ​​Also, take a look at web.dev framework-specific performance guidance for React and Angular that’s supposed to be expanded later this year (thanks, Phillip!).

CPU and compute performance of top-selling phones

CPU and compute performance of top-selling phones (Image credit: Addy Osmani) (Large preview)
  1. Consider using PRPL pattern and app shell architecture.
    Different frameworks will have different effects on performance and will require different strategies of optimization, so you have to clearly understand all of the nuts and bolts of the framework you’ll be relying on. When building a web app, look into the PRPL pattern and application shell architecture. The idea is quite straightforward: Push the minimal code needed to get interactive for the initial route to render quickly, then use service worker for caching and pre-caching resources and then lazy-load routes that you need, asynchronously.
PRPL Pattern in the application shell architecture
PRPL stands for Pushing critical resource, Rendering initial route, Pre-caching remaining routes and Lazy-loading remaining routes on demand.
Application shell architecture
An application shell is the minimal HTML, CSS, and JavaScript powering a user interface.
  1. Have you optimized the performance of your APIs?
    APIs are communication channels for an application to expose data to internal and third-party applications via so-called endpoints. When designing and building an API, we need a reasonable protocol to enable the communication between the server and third-party requests. Representational State Transfer (REST) is a well-established, logical choice: it defines a set of constraints that developers follow to make content accessible in a performant, reliable and scalable fashion. Web services that conform to the REST constraints, are called RESTful web services.

    As with good ol’ HTTP requests, when data is retrieved from an API, any delay in server response will propagate to the end user, hence delaying rendering. When a resource wants to retrieve some data from an API, it will need to request the data from the corresponding endpoint. A component that renders data from several resources, such as an article with comments and author photos in each comment, may need several roundtrips to the server to fetch all the data before it can be rendered. Furthermore, the amount of data returned through REST is often more than what is needed to render that component.

    If many resources require data from an API, the API might become a performance bottleneck. GraphQL provides a performant solution to these issues. Per se, GraphQL is a query language for your API, and a server-side runtime for executing queries by using a type system you define for your data. Unlike REST, GraphQL can retrieve all data in a single request, and the response will be exactly what is required, without over or under-fetching data as it typically happens with REST.

    In addition, because GraphQL is using schema (metadata that tells how the data is structured), it can already organize data into the preferred structure, so, for example, with GraphQL, we could remove JavaScript code used for dealing with state management, producing a cleaner application code that runs faster on the client.

    If you want to get started with GraphQL, Eric Baer published two fantastic articles on yours truly Smashing Magazine: A GraphQL Primer: Why We Need A New Kind Of API and A GraphQL Primer: The Evolution Of API Design (thanks for the hint, Leonardo!).

Hacker Noon

A difference between REST and GraphQL, illustrated via a conversation between Redux + REST on the left, an Apollo + GraphQL on the right. (Image source: Hacker Noon) (Large preview)
  1. Will you be using AMP or Instant Articles?
    Depending on the priorities and strategy of your organization, you might want to consider using Google’s AMP or Facebook’s Instant Articles or Apple’s Apple News. You can achieve good performance without them, but AMP does provide a solid performance framework with a free content delivery network (CDN), while Instant Articles will boost your visibility and performance on Facebook.

    The seemingly obvious benefit of these technologies for users is guaranteed performance, so at times they might even prefer AMP-/Apple News/Instant Pages-links over “regular” and potentially bloated pages. For content-heavy websites that are dealing with a lot of third-party content, these options could potentially help speed up render times dramatically.

    Unless they don’t. According to Tim Kadlec, for example, “AMP documents tend to be faster than their counterparts, but they don’t necessarily mean a page is performant. AMP is not what makes the biggest difference from a performance perspective.”

    A benefit for the website owner is obvious: discoverability of these formats on their respective platforms and increased visibility in search engines. You could build progressive web AMPs, too, by reusing AMPs as a data source for your PWA. Downside? Obviously, a presence in a walled garden places developers in a position to produce and maintain a separate version of their content, and in case of Instant Articles and Apple News without actual URLs (thanks Addy, Jeremy!).

  2. Choose your CDN wisely.
    Depending on how much dynamic data you have, you might be able to “outsource” some part of the content to a static site generator, pushing it to a CDN and serving a static version from it, thus avoiding database requests. You could even choose a static-hosting platform based on a CDN, enriching your pages with interactive components as enhancements (JAMStack). In fact, some of those generators (like Gatsby on top of React) are actually website compilers with many automated optimizations provided out of the box. As compilers add optimizations over time, the compiled output gets smaller and faster over time.

    Notice that CDNs can serve (and offload) dynamic content as well. So, restricting your CDN to static assets is not necessary. Double-check whether your CDN performs compression and conversion (e.g. image optimization in terms of formats, compression and resizing at the edge), support for servers workers, edge-side includes, which assemble static and dynamic parts of pages at the CDN’s edge (i.e. the server closest to the user), and other tasks. If you want to be on the edge, check if your CDN supports HTTP over QUIC (HTTP/3) as well.

    Note: based on research by Patrick Meenan and Andy Davies, HTTP/2 prioritization is effectively broken on many CDNs, so be careful when choosing a CDN. Patrick has more details in his recent talk on HTTP/2 Prioritization (thanks, Barry!).

Assets Optimizations

  1. Use Brotli for plain text compression.
    In 2015, Google introduced Brotli, a new open-source lossless data format, which is now supported in all modern browsers. In practice, Brotli appears to be much more effective than Gzip and Deflate. It might be (very) slow to compress, depending on the settings, but slower compression will ultimately lead to higher compression rates. Still, it decompresses fast. You can also estimate Brotli compression savings for your site.

    Browsers will accept it only if the user is visiting a website over HTTPS. Brotli is widely supported, and many CDNs support it (Akamai, AWS, KeyCDN, Fastly, Cloudlare, CDN77) and you can enable Brotli even on CDNs that don’t support it yet (with a service worker).

    The catch is that compressing all assets with Brotli is quite expensive, so a number of servers can’t use it just because of the cost overhead it produces. In fact, at the highest level of compression, Brotli is so slow that any potential gains in file size could be nullified by the amount of time it takes for the server to begin sending the response as it waits to dynamically compress the asset. With static compression, however, higher compression settings are preferred.

    If you can bypass the cost of dynamically compressing static assets, it’s worth the effort. Brotli can be used for any plaintext payload — HTML, CSS, SVG, JavaScript, and so on.

    The strategy? Pre-compress static assets with Brotli+Gzip at the highest level and compress (dynamic) HTML on the fly with Brotli at level 3–5. Make sure that the server handles content negotiation for Brotli or gzip properly.

A graph showing adoption of compression algorithms

Both on desktop and on mobile, only 15% of all requests are compressed with Brotli. Around 65% are compressed with gzip. The rest isn’t compressed at all. (Image source: Web Almanac: Compression) (Large preview)
  1. Use responsive images and WebP.
    As far as possible, use responsive images with srcset, sizes and the <picture> element. While you’re at it, you could also make use of the WebP format (supported in all modern browsers except Safari and iOS Safari) by serving WebP images with the <picture> element and a JPEG fallback (see Andreas Bovens’ code snippet) or by using content negotiation (using Accept headers). Ire Aderinokun has a very detailed tutorial on converting images to WebP, too.

    Sketch natively supports WebP, and WebP images can be exported from Photoshop using a WebP plugin for Photoshop. Other options are available, too. If you’re using WordPress or Joomla, there are extensions to help you easily implement support for WebP, such as Optimus and Cache Enabler for WordPress and Joomla’s own supported extension (via Cody Arsenault).

    It’s important to note that while WebP image file sizes compared to equivalent Guetzli and Zopfli, the format doesn’t support progressive rendering like JPEG, which is why users might see an actual image faster with a good ol’ JPEG although WebP images might get faster through the network. With JPEG, we can serve a “decent” user experience with the half or even quarter of the data and load the rest later, rather than have a half-empty image as it is in the case of WebP. Your decision will depend on what you are after: with WebP, you’ll reduce the payload, and with JPEG you’ll improve perceived performance.

    On Smashing Magazine, we use the postfix -opt for image names — for example, brotli-compression-opt.png; whenever an image contains that postfix, everybody on the team knows that the image has already been optimized. And — shameless plug! — Jeremy Wagner even published a Smashing book on WebP.

Responsive Image Breakpoints Generator
The Responsive Image Breakpoints Generator automates images and markup generation.
  1. Are images properly optimized?
    When you’re working on a landing page on which it’s critical that a particular image loads blazingly fast, make sure that JPEGs are progressive and compressed with mozJPEG (which improves the start rendering time by manipulating scan levels) or take a look at Guetzli, Google’s new open-source encoder focusing on perceptual performance, and utilizing learnings from Zopfli and WebP. The only downside: slow processing times (a minute of CPU per megapixel). For PNG, we can use Pingo, and for SVG, we can use SVGO or SVGOMG. And if you need to quickly preview and copy or download all the SVG assets from a website, svg-grabber can do that for you, too.

    Every single image optimization article would state it, but keeping vector assets clean and tight is always worth reminding. Make sure to clean up unused assets, remove unnecessary metadata and reduces the number of path points in artwork (and thus SVG code). (Thanks, Jeremy!)

    There are more advanced options though. You could:

    • Use Squoosh to compress, resize and manipulate images at the optimal compression levels (lossy or lossless),
    • Use the Responsive Image Breakpoints Generator or a service such as Cloudinary or Imgix to automate image optimization. Also, in many cases, using srcset and sizes alone will reap significant benefits.
    • To check the efficiency of your responsive markup, you can use imaging-heap, a command line tool that measure the efficiency across viewport sizes and device pixel ratios.
    • Lazy load images and iframes with hybrid lazy-loading, utilizing native lazy-loading and lazyload, a library that detects any visibility changes triggered through user interaction (with IntersectionObserver which we’ll explore later).
    • For offscreen images, we can display a placeholder first, and when the image is within the viewport, using IntersectionObserver, trigger a network call for the image to be downloaded in background. We can then defer render until decode with img.decode() or download the image if the Image Decode API isn’t available. When rendering the image, we can use fade-in animations, for example. Katie Hempenius and Addy Osmani share more insights in their talk Speed at Scale: Web Performance Tips and Tricks from the Trenches.
    • You can add automatic image compression to your Pull Requests, so no image can hit production uncompressed. The action uses mozjpeg and libvips that work with PNGs and JPGs.
    • Watch out for images that are loaded by default, but might never be displayed — e.g. in carousels, accordions and image galleries.
    • Consider Swapping Images with the Sizes Attribute by specifying different image display dimensions depending on media queries, e.g. to manipulate sizes to swap sources in a magnifier component.
    • Review image download inconsistencies to prevent unexpected downloads for foreground and background images.
    • Sometimes optimizing images alone won’t do the trick. To improve the time needed to start the rendering of a critical image, lazy-load less important images and defer any scripts to load after critical images have already rendered.
    • To optimize storage interally, you could use Dropbox’s new Lepton format for losslessly compressing JPEGs by an average of 22%.
    • Watch out for the aspect-ratio property in CSS and intrinsicsize attribute which will allow us to set aspect ratios and dimensions for images, so browser can reserve a pre-defined layout slot early to avoid layout jumps during the page load.
    • If you feel adventurous, you could chop and rearrange HTTP/2 streams using Edge workers, basically a real-time filter living on the CDN, to send images faster through the network. Edge workers use JavaScript streams that use chunks which you can control (basically they are JavaScript that runs on the CDN edge that can modify the streaming responses), so you can control the delivery of images. With service worker it’s too late as you can’t control what’s on the wire, but it does work with Edge workers. So you can use them on top of static JPEGs saved progressively for a particular landing page.

    A sample output by imaging-heap, a command line tool that measure the efficiency across viewport sizes and device pixel ratios. (Image source) (Large preview)

    The future of responsive images might change dramatically with the adoption of client hints. Client hints are HTTP request header fields, e.g. DPR, Viewport-Width, Width, Save-Data, Accept (to specify image format preferences) and others. They are supposed to inform the server about the specifics of user’s browser, screen, connection etc. As a result, the server can decide how to fill in the layout with appropriately sized images, and serve only these images in desired formats. With client hints, we move the resource selection from HTML markup and into the request-response negotiation between the client and server.

    As Ilya Grigorik noted, client hints complete the picture — they aren’t an alternative to responsive images. “The <picture> element provides the necessary art-direction control in the HTML markup. Client hints provide annotations on resulting image requests that enable resource selection automation. Service Worker provides full request and response management capabilities on the client.” A service worker could, for example, append new client hints headers values to the request, rewrite the URL and point the image request to a CDN, adapt response based on connectivity and user preferences, etc. It holds true not only for image assets but for pretty much all other requests as well.

    For clients that support client hints, one could measure 42% byte savings on images and 1MB+ fewer bytes for 70th+ percentile. On Smashing Magazine, we could measure 19-32% improvement, too. Unfortunately, client hints still have to gain some browser support. Still under consideration in Firefox. However, if you supply both the normal responsive images markup and the <meta> tag for Client Hints, then the browser will evaluate the responsive images markup and request the appropriate image source using the Client Hints HTTP headers.

    Not good enough? Well, you can also improve perceived performance for images with the multiple background images technique. Keep in mind that playing with contrast and blurring out unnecessary details (or removing colors) can reduce file size as well. Ah, you need to enlarge a small photo without losing quality? Consider using Letsenhance.io.

    These optimizations so far cover just the basics. Addy Osmani has published a very detailed guide on Essential Image Optimization that goes very deep into details of image compression and color management. For example, you could blur out unnecessary parts of the image (by applying a Gaussian blur filter to them) to reduce the file size, and eventually you might even start removing colors or turn the picture into black and white to reduce the size even further. For background images, exporting photos from Photoshop with 0 to 10% quality can be absolutely acceptable as well. Ah, and don’t use JPEG-XR on the web — “the processing of decoding JPEG-XRs software-side on the CPU nullifies and even outweighs the potentially positive impact of byte size savings, especially in the context of SPAs”.

Addy Osmani recommends to replace animated GIFs with looping inline videos. The file size difference is noticeable (80% savings). (Large preview)
  1. Are videos properly optimized?
    We covered images so far, but we’ve avoided a conversation about good ol’ GIFs. Frankly, instead of loading heavy animated GIFs which impact both rendering performance and bandwidth, it’s a good idea to switch either to animated WebP (with GIF being a fallback) or replace them with looping HTML5 videos altogether. Yes, unlike with images, browsers do not preload <video> content, but HTML5 videos tend to be lighter and smaller than GIFs. Not an option? Well, at least we can add lossy compression to GIFs with Lossy GIF, gifsicle or giflossy.

    Tests show that inline videos within img tags display 20× faster and decode 7× faster than the GIF equivalent, in addition to being a fraction in file size.

    In the land of good news, video formats have been advancing massively over the years. For a long time, we had hoped that WebM would become the format to rule them all, and WebP (which is basically one still image inside of the WebM video container) will become a replacement for dated image formats. But despite WebP and WebM gaining support these days, the breakthrough didn’t happen.

    In 2018, the Alliance of Open Media has released a new promising video format called AV1. AV1 has compression similar to the H.265 codec (the evolution of H.264) but unlike the latter, AV1 is free. The H.265 license pricing pushed browser vendors to adopt a comparably performant AV1 instead: AV1 (just like H.265) compresses twice as good as WebM.

    AV1 Logo 2018

    AV1 has good chances of becoming the ultimate standard for video on the web. (Image credit: Wikimedia.org) (Large preview)

    In fact, Apple currently uses HEIF format and HEVC (H.265), and all the photos and videos on the latest iOS are saved in these formats, not JPEG. While HEIF and HEVC (H.265) aren’t properly exposed to the web (yet?), AV1 is — and it’s gaining browser support. So adding the AV1 source in your <video> tag is reasonable, as all browser vendors seem to be on board.

    For now, the most widely used and supported encoding is H.264, served by MP4 files, so before serving the file, make sure that your MP4s are processed with a multipass-encoding, blurred with the frei0r iirblur effect (if applicable) and moov atom metadata is moved to the head of the file, while your server accepts byte serving. Boris Schapira provides exact instructions for FFmpeg to optimize videos to the maximum. Of course, providing WebM format as an alternative would help, too.

    Need to start rendering videos faster but videos files are still too large? For example, whenever hou have a large background video on a landing page? A common technique to use is to show the very first frame as a still image first, or display a heavily optimized, short looping segment that could be interpreted as a part of the video, and then, whenever the video is buffered enough, start playing the actual video. Doug Sillars has a written a detailed guide to background video performance that could be helpful in that case. (Thanks, Guy Podjarny!).

    Video playback performance is a story on its own, and if you’d like to dive into it in details, take a look at another Doug Sillars’ series on The Current State of Video and Video Delivery Best Practices that include details on video delivery metrics, video preloading, compression and streaming.

Zach Leatherman’s Comprehensive Guide to Font-Loading Strategies

Zach Leatherman’s Comprehensive Guide to Font-Loading Strategies provides a dozen options for better web font delivery.
  1. Are web fonts optimized?
    The first question that’s worth asking if you can get away with using UI system fonts in the first place — just make sure to double check that they appear correctly on various platforms. If it’s not the case, chances are high that the web fonts you are serving include glyphs and extra features and weights that aren’t being used. You can ask your type foundry to subset web fonts or if you are using open-source fonts, subset them on your own with Glyphhanger or Fontsquirrel. You can even automate your entire workflow with Peter Müller’s subfont, a command line tool that statically analyses your page in order to generate the most optimal web font subsets, and then inject them into your page.

    WOFF2 support is great, and you can use WOFF as fallback for browsers that don’t support it — or perhaps legacy browsers could be served well enough with system fonts instead. There are many, many, many options for web font loading, and you can choose one of the strategies from Zach Leatherman’s “Comprehensive Guide to Font-Loading Strategies,” (code snippets also available as Web font loading recipes).

    Probably the better options to consider today are Critical FOFT with preload and “The Compromise” method. Both of them use a two-stage render for delivering web fonts in steps — first a small supersubset required to render the page fast and accurately with the web font, and then load the rest of the family async. The difference is that “The Compromise” technique loads polyfill asynchronously only if font load events are not supported, so you don’t need to load the polyfill by default. Need a quick win? Zach Leatherman has a quick 23-min tutorial and case study to get your fonts in order.

    In general, it might be a good idea to use the preload resource hint to preload fonts, but in your markup include the hints after the link to critical CSS and JavaScript. With preload, there is a puzzle of priorities, so consider injecting rel="preload" elements into the DOM just before the external blocking scripts. According to Andy Davies, “resources injected using a script are hidden from the browser until the script executes, and we can use this behaviour to delay when the browser discovers the preload hint.” Otherwise, font loading will cost you in the first render time.

    It’s a good idea to be selective and choose files that matter most, e.g. the ones that are critical for rendering or that would help you avoiding visible and disruptive text reflows. In general, Zach advises to preload one or two fonts of each family — it also makes sense to delay some font loading if they are less critical.

    It has become quite common to use local() value (which refers to a lo­cal font by name) when defining a font-family in the @font-face rule:

    /* Warning! Probably not a good idea! */
    @font-face {
      font-family: Open Sans;
      src: local('Open Sans Regular'),
           local('OpenSans-Regular'),
           url('opensans.woff2') format ('woff2'),
           url('opensans.woff') format('woff');
    }

    The idea is reasonable: some popular open-source fonts such as Open Sans are coming pre-installed with some drivers or apps, so if the font is avail­able lo­cally, the browser does­n’t need to down­load the web font and can dis­play the lo­cal font im­me­di­ately. As Bram Stein noted, “though a lo­cal font matches the name of a web font, it most likely isn’t the same font. Many web fonts dif­fer from their “desk­top” ver­sion. The text might be ren­dered dif­fer­ently, some char­ac­ters may fall back to other fonts, Open­Type fea­tures can be miss­ing en­tirely, or the line height may be dif­fer­ent.”

    Also, as typefaces evolve over time, the locally installed version might be very different from the web font, with characters looking very different. So, according to Bram, it’s better to never mix lo­cally in­stalled fonts and web fonts in @font-face rules.

    Nobody likes waiting for the content to be displayed. With the font-display CSS descriptor, we can control the font loading behavior and enable content to be readable immediately (font-display: optional) or almost immediately (font-display: swap). However, if you want to avoid text reflows, we still need to use the Font Loading API, specifically to group repaints, or when you are using third party hosts. Unless you can use Google Fonts with Cloudflare Workers, of course.

    Talking about Google Fonts: although the support for font-display was added recently, consider using google-webfonts-helper, a hassle-free way to self-host Google Fonts. Always self-host your fonts for maximum control if you can.

    In general, if you use font-display: optional, it might not be a good idea to also use preload as it will trigger that web font request early (causing network congestion if you have other critical path resources that need to be fetched). Use preconnect for faster cross-origin font requests, but be cautious with preload as preloading fonts from a different origin wlll incur network contention. All of these techniques are covered in Zach’s Web font loading recipes.

    It might be a good idea to opt out of web fonts (or at least second stage render) if the user has enabled Reduce Motion in accessibility preferences or has opted in for Data Saver Mode (see Save-Data header). Or when the user happens to have slow connectivity (via Network Information API). Eventually, we might also be able to use prefers-reduced-data CSS media query to not define font declarations if the user has opted into data-saving mode. The media query would basically expose if the Save-Data request header from the Client Hint HTTP extension is on/off to allow for usage with CSS. Not quite there yet though.

    To measure the web font loading performance, consider the All Text Visible metric (the moment when all fonts have loaded and all content is displayed in web fonts), Time to Real Italics as well as Web Font Reflow Count after first render. Obviously, the lower both metrics are, the better the performance is. It’s important to notice that variable fonts might require a significant performance consideration. They give designers a much broader design space for typographic choices, but it comes at the cost of a single serial request opposed to a number of individual file requests. That single request might be slow, blocking the rendering of the content on a page. So subsetting and splitting the font into character sets will still matter. On the good side though, with a variable font in place, we’ll get exactly one reflow by default, so no JavaScript will be required to group repaints.

    Now, what would make a bulletproof web font loading strategy then? Subset fonts and prepare them for the 2-stage-render, declare them with a font-display descriptor, use Font Loading API to group repaints and store fonts in a persistent service worker’s cache. On the first visit, inject the preloading of scripts just before the blocking external scripts. You could fall back to Bram Stein’s Font Face Observer if necessary. And if you’re interested in measuring the performance of font loading, Andreas Marschke explores performance tracking with Font API and UserTiming API.

    Finally, don’t forget to include unicode-range to break down a large font into smaller language-specific fonts, and use Monica Dinculescu’s font-style-matcher to minimize a jarring shift in layout, due to sizing discrepancies between the fallback and the web fonts.

    Does the future look bright? With progressive font enrichment, eventually we might be able to “download only the required part of the font on any given page, and for subsequent requests for that font to dynamically ‘patch’ the original download with additional sets of glyphs as required on successive page views”, as Jason Pamental explains it. Incremental Transfer Demo is already available, and it’s work in progress.

Build Optimizations

  1. Set your priorities straight.
    It’s a good idea to know what you are dealing with first. Run an inventory of all of your assets (JavaScript, images, fonts, third-party scripts and “expensive” modules on the page, such as carousels, complex infographics and multimedia content), and break them down in groups.

    Set up a spreadsheet. Define the basic core experience for legacy browsers (i.e. fully accessible core content), the enhanced experience for capable browsers (i.e. the enriched, full experience) and the extras (assets that aren’t absolutely required and can be lazy-loaded, such as web fonts, unnecessary styles, carousel scripts, video players, social media buttons, large images). A while back, we published an article on “Improving Smashing Magazine’s Performance,” which describes this approach in detail.

    When optimizing for performance we need to reflect our priorities. Load the core experience immediately, then enhancements, and then the extras.

  2. Use native JavaScript modules in production.
    Remember the good ol’ cutting-the-mustard technique to send the core experience to legacy browsers and an enhanced experience to modern browsers? An updated variant of the technique could use ES2015+ <script type="module">, also known as module/nomodule pattern.

    As Philip Walton writes, “the technique uses bundlers and transpilers to generate two versions of your codebase, one with modern syntax (loaded via <script type="module">) and one with ES5 syntax (loaded via <script nomodule>).” Modern browsers would interpret the script as a JavaScript module and run it as expected, while legacy browsers wouldn’t recognize the attribute and ignore it because it’s unknown HTML syntax. We can ship significantly less code to module-supporting browsers, and it’s now supported by most frameworks and CLIs.

    One note of warning though: the module/nomodule pattern can backfire on some clients, so you might want to consider a workaround: Jeremy’s less risky differential serving pattern which, however, sidesteps the preload scanner, which could affect performance in ways one might not anticipate. (thanks, Jeremy!)

    In fact, Rollup supports modules as an output format, so we can both bundle code and deploy modules in production. Parcel has just added module support in Parcel 2. Webpack isn’t quite there yet. Also, watch out for Pika that is looking into simplifying build process and management of JavaScript modules.

    Note: It’s worth stating that feature detection alone isn’t enough to make an informed decision about the payload to ship to that browser. On its own, we can’t deduce device capability from browser version. For example, cheap Android phones in developing countries mostly run Chrome and will cut the mustard despite their limited memory and CPU capabilities.

    Eventually, using the Device Memory Client Hints Header, we’ll be able to target low-end devices more reliably. At the moment of writing, the header is supported only in Blink (it goes for client hints in general). Since Device Memory also has a JavaScript API which is available in Chrome, one option could be to feature detect based on the API, and fall back to module/nomodule technique if it’s not supported (thanks, Yoav!).

  3. Are you using tree-shaking, scope hoisting and code-splitting?
    Tree-shaking is a way to clean up your build process by only including code that is actually used in production and eliminate unused imports in Webpack. With Webpack and Rollup, we also have scope hoisting that allows both tools to detect where import chaining can be flattened and converted into one inlined function without compromising the code. With Webpack, we can also use JSON Tree Shaking as well.

    Also, you might want to consider learning how to avoid bloat and expensive styles. Feeling like going beyond that? You can also use Webpack to shorten the class names and use scope isolation
    to rename CSS class names dynamically at the compilation time.

    Code-splitting is another Webpack feature that splits your codebase into “chunks” that are loaded on demand. Not all of the JavaScript has to be downloaded, parsed and compiled right away. Once you define split points in your code, Webpack can take care of the dependencies and outputted files. It enables you to keep the initial download small and to request code on demand when requested by the application. Alexander Kondrov has a fantastic introduction to code-splitting with Webpack and React.

    Consider using preload-webpack-plugin that takes routes you code-split and then prompts browser to preload them using <link rel="preload"> or <link rel="prefetch">. Webpack inline directives also give some control over preload/prefetch. (Watch out for prioritization issues though.)

    Where to define split points? By tracking which chunks of CSS/JavaScript are used, and which aren’t used. Umar Hansa explains how you can use Code Coverage from Devtools to achieve it.

    If you aren’t using Webpack, note that Rollup shows significantly better results than good ol’ Browserify exports. While we’re at it, you might want to check out rollup-plugin-closure-compiler and Rollupify, which converts ECMAScript 2015 modules into one big CommonJS module — because small modules can have a surprisingly high performance cost depending on your choice of bundler and module system.

    When dealing with single-page applications, we need some time to initialize the app before we can render the page. Your setting will require your custom solution, but you could watch out for modules and techniques to speed up the initial rendering time. For example, here’s how to debug React performance and eliminate common React performance issues, and here’s how to improve performance in Angular. In general, most performance issues come from the initial time to bootstrap the app.

    So, what’s the best way to code-split aggressively, but not too aggressively? According to Phil Walton, “in addition to code-splitting via dynamic imports, [we could] also use code-splitting at the package level, where each imported node modules get put into a chunk based on its package’s name.” Phil provides a tutorial on how to build it as well.

  4. Can you offload JavaScript into a Web Worker?
    To reduce the negative impact to Time-to-Interactive, it might be a good idea to look into offloading heavy JavaScript into a Web Worker or caching via a Service Worker.

    As the code base keeps growing, the UI performance bottlenecks will show up, slowing down the user’s experience. That’s because DOM operations are running alongside your JavaScript on the main thread. With web workers, we can move these expensive operations to a background process that’s running on a different thread. Typical use cases for web workers are prefetching data and Progressive Web Apps to load and store some data in advance so that you can use it later when needed. And you could use Comlink to streamline the communication between the main page and the worker. Still some work to do, but we are getting there.

    How to get started? Here are a few resources that are worth looking into:

    Note that Web Workers don’t have access to the DOM because the DOM is not “thread-safe”, and the code that they execute needs to be contained in a separate file.

  5. Can you offload “hot paths” to WebAssembly?
    We could offload computationally heavy tasks off to WebAssembly (WASM), a binary instruction format, designed as a portable target for compilation of high-level languages like C/C++/Rust. Its browser support is remarkable, and it has recently become viable as function calls between JavaScript and WASM are getting faster. Plus, it’s even supported on Fastly’s edge cloud.

    Of course, WebAssembly isn’t supposed to replace JavaScript, but it can complement it in cases when you notice CPU hogs. For most web apps, JavaScript is a better fit, and WebAssembly is best used for computationally intensive web apps, such as web games.

    If you’d like to learn more about WebAssembly:

A general overview of how WebAssembly works and why it’s useful.

Milica Mihajlija provides a general overview of how WebAssembly works and why it’s useful. (Large preview)
  1. Are you using an ahead-of-time compiler?
    Make sure to use an ahead-of-time compiler to offload some of the client-side rendering to the server and, hence, output usable results quickly. Finally, consider using Optimize.js for faster initial loading by wrapping eagerly invoked functions (it might not be necessary any longer, though).
  2. Serve legacy code only to legacy browsers.
    With ES2015 being remarkably well supported in modern browsers, we can use babel-preset-env to only transpile ES2015+ features unsupported by the modern browsers you are targeting. Then set up two builds, one in ES6 and one in ES5. As mentioned above, JavaScript modules are now supported in all major browsers, so use use script type="module" to let browsers with ES module support load the file, while older browsers could load legacy builds with script nomodule. And we can automate the entire process with Webpack ESNext Boilerplate.

    Note that these days we can write module-based JavaScript that runs natively in the browser, without transpilers or bundlers. <link rel="modulepreload"> header provides a way to initiate early (and high-priority) loading of module scripts. Basically, it’s a nifty way to help in maximizing bandwidth usage, by telling the browser about what it needs to fetch so that it’s not stuck with anything to do during those long roundtrips. Also, Jake Archibald has published a detailed article with gotchas and things to keep in mind with ES Modules that’s worth reading.

    For lodash, use babel-plugin-lodash that will load only modules that you are using in your source. Your dependencies might also depend on other versions of Lodash, so transform generic lodash requires to cherry-picked ones to avoid code duplication. This might save you quite a bit of JavaScript payload.

    Shubham Kanodia has written a detailed low-maintenance guide on smart bundling: to shipping legacy code to only legacy browsers in production with the code snippet you could use right away.

As explained in Jake Archibald’s article, inline scripts are deferred until blocking external scripts and inline scripts are executed.

Jake Archibald has published a detailed article with gotchas and things to keep in mind with ES Modules, e.g. inline scripts are deferred until blocking external scripts and inline scripts are executed. (Large preview)
  1. Are you using module/nomodule pattern for JavaScript?
    We want to send just the necessary JavaScript through the network, yet it means being slightly more focused and granular about the delivery of those assets. A while back Philip Walton introduced the idea of module/nomodule pattern (also introduced by Jeremy Wagner as differential serving). The idea is to compile and serve two separate JavaScript bundles: the “regular” build, the one with Babel-transforms and polyfills and serve them only to legacy browsers that actually need them, and another bundle (same functionality) that has no transforms or polyfills.

    As a result, we help reduce blocking of the main thread by reducing the amount of scripts the browser needs to process. Jeremy Wagner has published a comprehensive article on differential serving and how to set it up in your build pipeline, from setting up Babel, to what tweaks you’ll need to make in Webpack, as well as the benefits of doing all this work.

  2. Identify and rewrite legacy code with incremental decoupling.
    Long-living projects have a tendency to gather dust and dated code. Revisit your dependencies and assess how much time would be required to refactor or rewrite legacy code that has been causing trouble lately. Of course, it’s always a big undertaking, but once you know the impact of the legacy code, you could start with incremental decoupling.

    First, set up metrics that tracks if the ratio of legacy code calls is staying constant or going down, not up. Publicly discourage the team from using the library and make sure that your CI alerts developers if it’s used in pull requests. polyfills could help transition from legacy code to rewritten codebase that uses standard browser features.

  3. Identify and remove unused CSS/JS.
    CSS and JavaScript code coverage in Chrome allows you to learn which code has been executed/applied and which hasn’t. You can start recording the coverage, perform actions on a page, and then explore the code coverage results. Once you’ve detected unused code, find those modules and lazy load with import() (see the entire thread). Then repeat the coverage profile and validate that it’s now shipping less code on initial load.

    You can use Puppeteer to programmatically collect code coverage and Canary already allows you to export code coverage results, too. As Andy Davies noted, you might want to collect code coverage for both modern and legacy browsers though.

    There are many other use-cases for Puppeteer, such as, for example, automatic visual diffing or monitoring unused CSS with every build. If you’re looking for a detailed guide to Puppeteer, Nitay Neeman has a very comprehensive overview of Puppeteer, with examples and use cases.

    Furthermore, purgecss, UnCSS and Helium can help you remove unused styles from CSS. And if you aren’t certain if a suspicious piece of code is used somewhere, you can follow Harry Roberts’ advice: create a 1×1px transparent GIF for a particular class and drop it into a dead/ directory, e.g. /assets/img/dead/comments.gif. After that, you set that specific image as a background on the corresponding selector in your CSS, sit back and wait for a few months if the file is going to appear in your logs. If there are no entries, nobody had that legacy component rendered on their screen: you can probably go ahead and delete it all.

    For the I-feel-adventurous-department, you could even automate gathering on unused CSS through a set of pages by monitoring DevTools using DevTools.

  4. Trim the size of your JavaScript bundles.
    As Addy Osmani noted, there’s a high chance you’re shipping full JavaScript libraries when you only need a fraction, along with dated polyfills for browsers that don’t need them, or just duplicate code. To avoid the overhead, consider using webpack-libs-optimizations that removes unused methods and polyfills during the build process.

    Add bundle auditing into your regular workflow as well. There might be some lightweight alternatives to heavy libraries you’ve added years ago, e.g. Moment.js could be replaced with native Internationalization API, date-fns or Luxon. Benedikt Rötsch’s research showed that a switch from Moment.js to date-fns could shave around 300ms for First paint on 3G and a low-end mobile phone.

    That’s where tools like Bundlephobia could help find the cost of adding a npm package to your bundle. size-limit extends basic bundle size check with details on JavaScript execution time. You can even integrate these costs with a Lighthouse Custom Audit. This goes for frameworks, too. By removing or trimming the Vue MDC Adapter (Material Components for Vue), styles drop from 194KB to 10KB.

    Feeling adventurous? You could look into Prepack. It compiles JavaScript to equivalent JavaScript code, but unlike Babel or Uglify, it lets you write normal JavaScript code, and outputs equivalent JavaScript code that runs faster.

    Alternatively to shipping the entire framework, you could even trim your framework and compile it into a raw JavaScript bundle that does not require additional code. Svelte does it, and so does Rawact Babel plugin which transpiles React.js components to native DOM operations at build-time. Why? Well, as maintainers explain, “react-dom includes code for every possible component/HTMLElement that can be rendered, including code for incremental rendering, scheduling, event handling, etc. But there are applications that do not need all these features (at initial page load). For such applications, it might make sense to use native DOM operations to build the interactive user interface.”

size-limit provides basic bundle size check with details on JavaScript execution time as well

size-limit provides basic bundle size check with details on JavaScript execution time as well. (Large preview)

Webpack comparison

In his article, Benedikt Rötsch’s showed that a switch from Moment.js to date-fns could shave around 300ms for First paint on 3G and a low-end mobile phone. (Large preview)
  1. Are you using predictive prefetching for JavaScript chunks?
    We could use heuristics to decide when to preload JavaScript chunks. Guess.js is a set of tools and libraries that use Google Analytics data to determine which page a user is most likely to visit next from a given page. Based on user navigation patterns collected from Google Analytics or other sources, Guess.js builds a machine-learning model to predict and prefetch JavaScript that will be required on each subsequent page.

    Hence, every interactive element is receiving a probability score for engagement, and based on that score, a client-side script decides to prefetch a resource ahead of time. You can integrate the technique to your Next.js application, Angular and React, and there is a Webpack plugin which automates the setup process as well.

    Obviously, you might be prompting the browser to consume unneeded data and prefetch undesirable pages, so it’s a good idea to be quite conservative in the number of prefetched requests. A good use case would be prefetching validation scripts required in the checkout, or speculative prefetch when a critical call-to-action comes into the viewport.

    Need something less sophisticated? DNStradamus does DNS prefetching for outbound links as they appear in the viewport. Quicklink and Instant.page are small libraries that automatically prefetch links in the viewport during idle time in attempt to make next-page navigations load faster. Quicklink is data-considerate, so it doesn’t prefetch on 2G or if Data-Saver is on, and so is Instant.page if the mode is set to use viewport prefetching (which is a default).

  2. Take advantage of optimizations for your target JavaScript engine.
    Study what JavaScript engines dominate in your user base, then explore ways of optimizing for them. For example, when optimizing for V8 which is used in Blink-browsers, Node.js runtime and Electron, make use of script streaming for monolithic scripts.

    Script streaming allows async or defer scripts to be parsed on a separate background thread once downloading begins, hence in some cases improving page loading times by up to 10%. Practically, use <script defer> in the <head>, so that the browsers can discover the resource early and then parse it on the background thread.

    Caveat: Opera Mini doesn’t support script deferment, so if you are developing for India or Africa, defer will be ignored, resulting in blocking rendering until the script has been evaluated (thanks Jeremy!).

    You could also hook into V8’s code caching as well, by splitting out libraries from code using them, or the other way around, merge libraries and their uses into a single script, group small files together and avoid inline scripts. Or perhaps even use v8-compile-cache.

    Firefox’s recently released Baseline Interpreter has speed up Firefox and there are a few JIT Optimization Strategies available as well.


Progressive booting
Progressive booting means using server-side rendering to get a quick first meaningful paint, but also include some minimal JavaScript to keep the time-to-interactive close to the first meaningful paint.
  1. Client-side rendering or server-side rendering? Both!
    That’s a quite heated conversation to have. Ultimately, the decision has to be driven by the performance of the application. The ultimate approach would be to set up some sort of progressive booting: Use server-side rendering to get a quick first meaningful paint, but also include some minimal necessary JavaScript to keep the time-to-interactive close to the first meaningful paint. If JavaScript is coming too late after the First Meaningful Paint, the browser will lock up the main thread while parsing, compiling and executing late-discovered JavaScript, hence handcuffing the interactivity of site or application.

    To avoid it, always break up the execution of functions into separate, asynchronous tasks, and where possible use requestIdleCallback. Consider lazy loading parts of the UI using WebPack’s dynamic import() support, avoiding the load, parse, and compile cost until users really need them (thanks Addy!).

    In its essence, Time to Interactive (TTI) tells us the time between navigation and interactivity. The metric is defined by looking at the first five-second window after the initial content is rendered, in which no JavaScript tasks take longer than 50ms. If a task over 50ms occurs, the search for a five-second window starts over. As a result, the browser will first assume that it reached Interactive, just to switch to Frozen, just to eventually switch back to Interactive.

    Once we reached Interactive, we can then — either on demand or as time allows — boot non-essential parts of the app. Unfortunately, as Paul Lewis noticed, frameworks typically have no simple concept of priority that can be surfaced to developers, and hence progressive booting isn’t easy to implement with most libraries and frameworks.

    Still, we are getting there. These days there are a couple of choices we can explore, and Houssein Djirdeh and Jason Miller provide an excellent overview of these options in their talk on Rendering on the Web. The overview below is based on their talk.

    • Full Server-Side Rendering (SSR)
      In classic SSR, such as WordPress, all requests are handled entirely on the server. The requested content is returned as a finished HTML page and browsers can render it right away. Hence, SSR-apps can’t really make use of the DOM APIs, for example. The gap between First Contentful Paint and Time to Interactive is usually small, and the page can be rendered right away as HTML is being streamed to the browser. However, we end up with longer server think time and consequently Time To First Byte and we don’t make use of responsive and rich features of modern applications.

    • Static SSR (SSR)
      We build out the product as a single page application, but all pages are prerendered to static HTML with minimal JavaScript as a build step. Thus, we can display a landing page quickly and then prefetch a SPA-framework for subsequent pages. Netflix has adopted this approach decreasing loading and Time-to-Interactive by 50%.

    • Server-Side Rendering With (Re)Hydration (SSR + CSR)
      With hydration in the mix, the HTML page returned from the server also contains a script that loads a fully-fledged client-side application.

      With React, we can use ReactDOMServer module on a Node server like Express, and then call the renderToString method to render the top level components as a static HTML string. With Vue, we can use the vue-server-renderer to render a Vue instance into HTML using renderToString. In Angular, we can use @nguniversal to turn client requests into fully server-rendered HTML pages.

      A fully server-rendered experience can also be achieved out of the box with Next.js (React) or Nuxt.js (Vue).

      The approach has its downsides. As a result, we do gain full flexibility of client-side apps while providing faster server-side rendering, but we also end up with a longer gap between First Meaningful Paint and Time To Interactive and increased First Input Delay. Rehydration is very expensive, and usually this strategy alone will not be good enough as it heavily delays Time To Interactive.

    • Streaming Server-Side Rendering With Progressive Hydration (SSR + CSR)
      To minimize the gap between Time To Interactive and First Contentful Paint, we render multiple requests at once and send down content in chunks as they get generated. So we don’t have to wait for the full string of HTML before sending content to the browser, and hence improve Time To First Byte.

      In React, instead of renderToString, we can use renderToNodeStream to pipe the response and send the HTML down in chunks. In Vue, we can use renderToStream that can be piped and streamed. With React Suspense on the horizon, we might use asynchronous rendering for that purpose, too.

      On the client-side, rather than booting the entire application at once, we boot up components progressively. Sections of the applications are first broken down into standalone scripts with code splitting, and then hydrated gradually (in order of our priorities). In fact, we can hydrate critical components first, while the rest could be hydrated later. The role of client-side and server-side rendering can then be defined differently per component. We can then also defer hydration of some components until they come into view, or are needed for user interaction, or when the browser is idle.

      For Vue, Markus Oberlehner has published a guide on reducing Time To Interactive of SSR apps using hydration on user interaction as well as vue-lazy-hydration, an early-stage plugin that enables component hydration on visibility or specific user interaction. The Angular team works on progressive hydration with Ivy Universal. You can implement partial hydration with Preact and Next.js, too.

      For React, partial hydration is on the Suspense roadmap (and it looks promising!). If you feel adventurous, Jason Miller has published working demos on how progressive hydration could be implemented with React, so you can use them right away: demo 1, demo 2, demo 3 (also available on GitHub). Plus, you can look into the react-prerendered-component library.

    • Trisomorphic Rendering
      With service workers in place, we can use streaming server rendering for initial/non-JS navigations, and then have the service worker taking on rendering of HTML for navigations after it has been installed. In that case, service worker prerenders content and enables SPA-style navigations for rendering new views in the same session. Works well when you can share the same templating and routing code between the server, client page, and service worker.

    Trisomorphic rendering, with the same code rendering in any 3 places: on the server, in the DOM or in a service worker. (Image source: Google Developers) (Large preview)
    • CSR With Prerendering
      Prerendering is similar to server-side rendering but rather than rendering pages on the server dynamically, we render the application to static HTML at build time.

      Gatsby, an open source static site generator that uses React, uses renderToStaticMarkup method instead of renderToString method during builds, with main JS chunk being preloaded and future routes are prefetched, without DOM attributes that aren’t needed for simple static pages. For Vue, we can use Vuepress to achieve the same goal. You can also use prerender-loader with Webpack.

      The result is a better Time To First Byte and First Contentful Paint, and we reduce the gap between Time To Interactive and First Contentful Paint. We can’t use the approach if the content is expected to change much. Plus, all URLs have to be known ahead of time to generate all the pages. So some components might be rendered using prerendering, but if we need something dynamic, we have to rely on the app to fetch the content.

    • Full Client-Side Rendering (CSR)
      All logic, rendering and booting are done on the client. The result is usually a huge gap between Time-To-Interactive and First Contentful Paint. As a result, applications feel sluggish as the entire app has to be booted on the client to render anything. In general, SSR is faster than CSR. Yet still, It’s a most frequent implementation for many apps out there.

    So, client-side or server-side? In general, it’s a good idea to limit the use of fully client-side frameworks to pages that absolutely require them. For advanced applications, it’s not a good idea to rely on server-side rendering alone either. Both server-rendering and client-rendering are a disaster if done poorly.

    Whether you are leaning towards CSR or SSR, make sure that you are rendering important pixels as soon as possible and minimize the gap between that rendering and Time To Interactive. Consider prerendering if your pages don’t change much, and defer the booting of frameworks if you can. Stream HTML in chunks with server-side rendering, and implement progressive hydration for client-side rendering — and hydrate on visibility, interaction or during idle time to get the best of both worlds.

The spectrum of options for client-side versus server-side rendering. Also, check Jason’s and Houssein’s talk at Google I/O on Performance Implications of Application Architecture. (Image source: Jason Miller) (Large preview)

AirBnB has been experimenting with progressive hydration; they defer unneeded components, load on user interaction (scroll) or during idle time and testing show that it can improve TTI. (Large preview)
  1. Always prefer to self-host third-party assets.
    In general, it’s a good rule of thumb to self-host your static assets by default. It’s common to assume that if many sites use the same public CDN and the same version of a JavaScript library or a web font, then the visitors would land on our site with the scripts and fonts already cached in their browser, speeding up their experience considerably. However, it’s very unlikely to happen.

    For security reasons, to avoid fingerprinting, browsers have been implementing partitioned caching that was introduced in Safari back in 2013, and in Chrome last year. So if two sites point to the exact same third-party resource URL, the code is downloaded once per domain, and the cache is “sandboxed” to that domain due to privacy implications (thanks, David Calhoun!).
    Hence, using a public CDN will not automatically lead to better performance.

    Furthermore, it’s worth noting that resources don’t live in the browser’s cache as long as we might expect, and first-party assets are more likely to stay in the cache than third-party assets. Therefore, self-hosting is usually more reliable and secure, and better for performance, too.

  2. Constrain the impact of third-party scripts.
    With all performance optimizations in place, often we can’t control third-party scripts coming from business requirements. Third-party-scripts metrics aren’t influenced by end-user experience, so too often one single script ends up calling a long tail of obnoxious third-party scripts, hence ruining a dedicated performance effort. To contain and mitigate performance penalties that these scripts bring along, it’s not enough to just load them asynchronously (probably via defer) and accelerate them via resource hints such as dns-prefetch or preconnect.

    57% of all JavaScript code excution time is spent on third-party code, so regularly auditing your dependencies and tag managers is important.

    As Yoav Weiss explained in his must-watch talk on third-party scripts, in many cases these scripts download resources that are dynamic. The resources change between page loads, so we don’t necessarily know which hosts the resources will be downloaded from and what resources they would be.

    What options do we have then? Consider using service workers by racing the resource download with a timeout and if the resource hasn’t responded within a certain timeout, return an empty response to tell the browser to carry on with parsing of the page. You can also log or block third-party requests that aren’t successful or don’t fulfill certain criteria. If you can, load the 3rd-party-script from your own server rather than from the vendor’s server and lazy load them. E.g. Huddle has avoided 2.3 MB chat widget on page load by creating a fake chat button which downloads the script only when clicked. This avoids the unnecessary download and JavaScript execution for the majority of users who don’t engage with the chat widget.

    Another option is to establish a Content Security Policy (CSP) to restrict the impact of third-party scripts, e.g. disallowing the download of audio or video. The best option is to embed scripts via <iframe> so that the scripts are running in the context of the iframe and hence don’t have access to the DOM of the page, and can’t run arbitrary code on your domain. Iframes can be further constrained using the sandbox attribute, so you can disable any functionality that iframe may do, e.g. prevent scripts from running, prevent alerts, form submission, plugins, access to the top navigation, and so on.

    For example, it’s probably going to be necessary to allow scripts to run with <iframe sandbox="allow-scripts">. Each of the limitations can be lifted via various allow values on the sandbox attribute (supported almost everywhere), so constrain them to the bare minimum of what they should be allowed to do.

    Consider using Intersection Observer; that would enable ads to be iframed while still dispatching events or getting the information that they need from the DOM (e.g. ad visibility). Watch out for new policies such as Feature policy, resource size limits and CPU/Bandwidth priority to limit harmful web features and scripts that would slow down the browser, e.g. synchronous scripts, synchronous XHR requests, document.write and outdated implementations.

    To stress-test third parties, examine bottom-up summaries in Performance profile page in DevTools, test what happens if a request is blocked or it has timed out — for the latter, you can use WebPageTest’s Blackhole server blackhole.webpagetest.org that you can point specific domains to in your hosts file. Preferably self-host and use a single hostname, but also generate a request map that exposes fourth-party calls and detect when the scripts change. You can use Harry Roberts’ approach for auditing third parties and produce spreadsheets like this one. Harry also explains the auditing workflow in his talk on third-party performance and auditing.

    Have to deal with almighty Google Tag Manager? Barry Pollards provides some guidelines to contain the impact of Google Tag Manager. Also, Christian Schaefer explores strategies for loading ads in 2020.

Casper.com published a detailed case study on how they managed to shave 1.7 seconds off the site by self-hosting Optimizely. It might be worth it.

Casper.com published a detailed case study on how they managed to shave 1.7 seconds off the site by self-hosting Optimizely. It might be worth it. (Image source) (Large preview)
  1. Set HTTP cache headers properly.
    Double-check that expires, max-age, cache-control, and other HTTP cache headers have been set properly. In general, resources should be cacheable either for a very short time (if they are likely to change) or indefinitely (if they are static) — you can just change their version in the URL when needed.

    Use Cache-control: immutable, designed for fingerprinted static resources, to avoid revalidation (supported in Firefox, Edge and Safari). In fact, according to Web Almanac, “its usage has grown to 3.4%, and it’s widely used in Facebook and Google third-party responses.”

    Remember the stale-while-revalidate? As you probably know, we specify the caching time with the Cache-Control response header, e.g. Cache-Control: max-age=604800. After 604800 seconds have passed, the cache will re-fetch the requested content, causing the page to load slower. This slowdown can be avoided by using stale-while-revalidate; it basically defines an extra window of time during which a cache can use a stale asset as long as it revalidates it async in the background. Thus, it “hides” latency (both in the network and on the server) from clients.

    In June–July 2019, Chrome and Firefox launched support of stale-while-revalidate in HTTP Cache-Control header, so as a result, it should improve subsequent page load latencies as stale assets are no longer in the critical path. Result: zero RTT for repeat views.

    You can use Heroku’s primer on HTTP caching headers, Jake Archibald’s “Caching Best Practices” and Ilya Grigorik’s HTTP caching primer as guides. Also, be wary of the vary header, especially in relation to CDNs, and watch out for the Key header which helps avoiding an additional round trip for validation whenever a new request differs slightly (but not significantly) from prior requests (thanks, Guy!).

    Also, double-check that you aren’t sending unnecessary headers (e.g. x-powered-by, pragma, x-ua-compatible, expires and others) and that you include useful security and performance headers (such as Content-Security-Policy, X-XSS-Protection, X-Content-Type-Options and others). Finally, keep in mind the performance cost of CORS requests in single-page applications.

Delivery Optimizations

  1. Do you load all JavaScript libraries asynchronously?
    When the user requests a page, the browser fetches the HTML and constructs the DOM, then fetches the CSS and constructs the CSSOM, and then generates a rendering tree by matching the DOM and CSSOM. If any JavaScript needs to be resolved, the browser won’t start rendering the page until it’s resolved, thus delaying rendering. As developers, we have to explicitly tell the browser not to wait and to start rendering the page. The way to do this for scripts is with the defer and async attributes in HTML.

    In practice, it turns out we should prefer defer to async (at a cost to users of Internet Explorer up to and including version 9, because you’re likely to break scripts for them). According to Steve Souders, once async scripts arrive, they are executed immediately. If that happens very fast, for example when the script is in cache aleady, it can actually block HTML parser. With defer, browser doesn’t execute scripts until HTML is parsed. So, unless you need JavaScript to execute before start render, it’s better to use defer.

    Also, as mentioned above, limit the impact of third-party libraries and scripts, especially with social sharing buttons and <iframe> embeds (such as maps). Size Limit helps you prevent JavaScript libraries bloat: If you accidentally add a large dependency, the tool will inform you and throw an error. You can use static social sharing buttons (such as by SSBG) and static links to interactive maps instead.

    You might want to revise your non-blocking script loader for CSP compliance.

  2. Lazy load expensive components with IntersectionObserver and priority hints.
    In general, it’s a good idea to lazy-load all expensive components, such as heavy JavaScript, videos, iframes, widgets, and potentially images. Native lazy-loading is already available for images and iframes, and we can use importance attribute (high or low) on a <script>, <img>, or <link> element (Blink only). In fact, it’s a great way to deprioritize images in carousels or fectes, as well as re-prioritize scripts. However, sometimes we might need a bit more granular control.

    The most performant way to do lazy load script is by using the Intersection Observer API that provides a way to asynchronously observe changes in the intersection of a target element with an ancestor element or with a top-level document’s viewport. Basically, you need to create a new IntersectionObserver object, which receives a callback function and a set of options. Then we add a target to observe.

    The callback function executes when the target becomes visible or invisible, so when it intercepts the viewport, you can start taking some actions before the element becomes visible. In fact, we have a granular control over when the observer’s callback should be invoked, with rootMargin (margin around the root) and threshold (a single number or an array of numbers which indicate at what percentage of the target’s visibility we are aiming).

    Alejandro Garcia Anglada has published a handy tutorial on how to actually implement it, Rahul Nanwani wrote a detailed post on lazy-loading foreground and background images, and Google Fundamentals provide a detailed tutorial on lazy loading images and video with Intersection Observer as well. Remember art-directed storytelling long reads with moving and sticky objects? You can implement performant scrollytelling with Intersection Observer, too.

    Also, watch out for the Feature policy: LazyLoad will provide a mechanism that allows us to force opting in or out of LazyLoad functionality on a per-domain basis (similar to how Content Security Policies work).

    Check again what else you could lazy load. Even lazy-loading translation strings and emoji could help. By doing so, Mobile Twitter managed to achieve 80% faster JavaScript execution from the new internationalization pipeline.

By lazy-loading translation strings, Mobile Twitter managed to achieve 80% faster JavaScript execution from the new internationalization pipeline. (Image credit: Addy Osmani) (Large preview)
  1. Load images progressively.
    You could even take lazy loading to the next level by adding progressive image loading to your pages. Similarly to Facebook, Pinterest and Medium, you could load low quality or even blurry images first, and then as the page continues to load, replace them with the full quality versions by using the LQIP (Low Quality Image Placeholders) technique proposed by Guy Podjarny.

    Opinions differ if these techniques improve user experience or not, but it definitely improves time to first meaningful paint. We can even automate it by using SQIP that creates a low quality version of an image as an SVG placeholder, or Gradient Image Placeholders with CSS linear gradients. These placeholders could be embedded within HTML as they naturally compress well with text compression methods. In his article, Dean Hume has described how this technique can be implemented using Intersection Observer.

    Browser support? Decent, with Chrome, Firefox, Edge and Samsung Internet being on board. WebKit status is currently supported in preview. Fallback? If the browser doesn’t support intersection observer, we can still lazy load a polyfill or load the images immediately. And there is even a library for it.

    Want to go fancier? You could trace your images and use primitive shapes and edges to create a lightweight SVG placeholder, load it first, and then transition from the placeholder vector image to the (loaded) bitmap image.

  2. SVG lazy loading technique by José M. Pérez

    SVG lazy loading technique by José M. Pérez. (Large preview)
  3. Do you send critical CSS?
    To ensure that browsers start rendering your page as quickly as possible, it’s become a common practice to collect all of the CSS required to start rendering the first visible portion of the page (known as “critical CSS” or “above-the-fold CSS”) and add it inline in the <head> of the page, thus reducing roundtrips. Due to the limited size of packages exchanged during the slow start phase, your budget for critical CSS is around 14KB. (This specific limitation doesn’t apply with TCP BBR in place although it’s still important to prioritize critical resources and load them as early as possible).

    If you go beyond that, the browser will need additional roundtrips to fetch more styles. CriticalCSS and Critical enable you to discover critical CSS. You might need to do it for every template you’re using.

    You can then inline critical CSS and lazy-load the rest with critters Webpack plugin. If possible, consider using the conditional inlining approach used by the Filament Group, or convert inline code to static assets on the fly.

    If you load your full CSS asynchronously with libraries such as loadCSS, it’s not really necessary. With media="print" on link, you can trick browser into fetching the CSS asynchronously but applying to the screen environment once it loads. (thanks, Scott!)

    With HTTP/2, critical CSS could be stored in a separate CSS file and delivered via a server push without bloating the HTML. The catch is that server pushing is troublesome with many gotchas and race conditions across browsers. It isn’t supported consistently and has some caching issues (see slide 114 onwards of Hooman Beheshti’s presentation). The effect could, in fact, be negative and bloat the network buffers, preventing genuine frames in the document from being delivered. Also, it appears that server pushing is much more effective on warm connections due to the TCP slow start.

    Even with HTTP/1, putting critical CSS (and other important assets) in a separate file on the root domain has benefits, sometimes even more than inlining due to caching. Chrome speculatively opens a second HTTP connection to the root domain when requesting the page, which removes the need for a TCP connection to fetch this CSS (thanks, Philip!)

    A few gotchas to keep in mind: unlike preload that can trigger preload from any domain, you can only push resources from your own domain or domains you are authoritative for. It can be initiated as soon as the server gets the very first request from the client. Server-pushed resources land in the Push cache and are removed when the connection is terminated. However, since an HTTP/2 connection can be re-used across multiple tabs, pushed resources can be claimed by requests from other tabs as well. We can’t depend on it though, especially in Safari and Edge (thanks, Inian, Barry!).

    At the moment, there is no simple way for the server to know if pushed resources are already in one of the user’s caches, so resources will keep being pushed with every user’s visit. You may then need to create a cache-aware HTTP/2 server push mechanism. If fetched, you could try to get them from a cache based on the index of what’s already in the cache, avoiding secondary server pushes altogether.

    For a while, the cache-digest specification was considered to help negate the need to manually build such “cache-aware” servers, basically declaring a new frame type in HTTP/2 to communicate what’s already in the cache for that hostname. However, cache-digest spec was abandoned, so the solution isn’t quite in sight yet. (thanks, Barry!).

    For dynamic content, when a server needs some time to generate a response, the browser isn’t able to make any requests since it’s not aware of any sub-resources that the page might reference. For that case, we can warm up the connection and increase the TCP congestion window size, so that future requests can be completed faster. Also, all inlined assets are usually good candidates for server pushing. In fact, Inian Parameshwaran did remarkable research comparing HTTP/2 Push vs. HTTP Preload, and it’s a fantastic read with all the details you might need.

    Bottom line: As Sam Saccone noted, preload is good for moving the start download time of an asset closer to the initial request, while Server Push is good for cutting out a full RTT (or more, depending on your server think time) — if you have a service worker to prevent unnecessary pushing, that is.

  4. Experiment with regrouping your CSS rules.
    We’ve got used to critical CSS, but there are a few optimizations that could go beyond that. Harry Roberts conducted a remarkable research with quite surprising results. For example, it might be a good idea to split the main CSS file out into its individual media queries. That way, the browser will retrieve critical CSS with high priority, and everything else with low priority — completely off the critical path.

    Also, avoid placing <link rel="stylesheet" /> before async snippets. If scripts don’t depend on stylesheets, consider placing blocking scripts above blocking styles. If they do, split that JavaScript in two and load it either side of your CSS.

    Scott Jehl solved another interesting problem by caching an inlined CSS file with a service worker, a common problem familiar if you’re using critical CSS. Basically, we add an ID attribute onto the style element so that it’s easy to find it using JavaScript, then a small piece of JavaScript finds that CSS and uses the Cache API to store it in a local browser cache (with a content type of text/css) for use on subsequent pages. To avoid inlining on subsequent pages and instead reference the cached assets externally, we then set a cookie on the first visit to a site. Voilà!

    It’s worth noting that dynamic styling can be expensive, too, but usually only in cases when you rely on hundreds of concurrently rendered composed components. So if you’re using CSS-in-JS, make sure that your CSS-in-JS library optimizes the execution when your CSS has no dependencies on theme or props, and don’t over-compose styled components. Aggelos Arvanitakis shares more insights into performance costs of CSS-in-JS.

Do we stream reponses? With streaming, HTML rendered during the initial navigation request can take full advantage of the browser’s streaming HTML parser.
  1. Do you stream responses?
    Often forgotten and neglected, streams provide an interface for reading or writing asynchronous chunks of data, only a subset of which might be available in memory at any given time. Basically, they allow the page that made the original request to start working with the response as soon as the first chunk of data is available, and use parsers that are optimized for streaming to progressively display the content.

    We could create one stream from multiple sources. For example, instead of serving an empty UI shell and letting JavaScript populate it, you can let the service worker construct a stream where the shell comes from a cache, but the body comes from the network. As Jeff Posnick noted, if your web app is powered by a CMS that server-renders HTML by stitching together partial templates, that model translates directly into using streaming responses, with the templating logic replicated in the service worker instead of your server. Jake Archibald’s The Year of Web Streams article highlights how exactly you could build it. Performance boost is quite noticeable.

    One important advantage of streaming the entire HTML response is that HTML rendered during the initial navigation request can take full advantage of the browser’s streaming HTML parser. Chunks of HTML that are inserted into a document after the page has loaded (as is common with content populated via JavaScript) can’t take advantage of this optimization.

    Browser support? Getting there with partial support in Chrome, Firefox, Safari and Edge supporting the API and Service Workers being supported in all modern browsers.

  2. Consider making your components connection-aware.
    Data can be expensive and with growing payload, we need to respect users who choose to opt into data savings while accessing our sites or apps. The Save-Data client hint request header allows us to customize the application and the payload to cost- and performance-constrained users. In fact, you could rewrite requests for high DPI images to low DPI images, remove web fonts, fancy parallax effects, preview thumbnails and infinite scroll, turn off video autoplay, server pushes, reduce the number of displayed items and downgrade image quality, or even change how you deliver markup. Tim Vereecke has published a very detailed article on data-s(h)aver strategies featuring many options for data saving.

    The header is currently supported only in Chromium, on the Android version of Chrome or via the Data Saver extension on a desktop device. Finally, you can also use the Network Information API to deliver low/high resolution images and videos based on the network type. Network Information API and specifically navigator.connection.effectiveType use RTT, downlink, effectiveType values (and a few others) to provide a representation of the connection and the data that users can handle.

    In this context, Max Stoiber speaks of connection-aware components and Addy Osmani speaks of adaptive module serving. For example, with React, we could write a component that renders differently for different connection types. As Max suggested, a <Media /> component in a news article might output:

    • Offline: a placeholder with alt text,
    • 2G / save-data mode: a low-resolution image,
    • 3G on non-Retina screen: a mid-resolution image,
    • 3G on Retina screens: high-res Retina image,
    • 4G: an HD video.

    Dean Hume provides a practical implementation of a similar logic using a service worker. For a video, we could display a video poster by default, and then display the “Play” icon as well as the video player shell, meta-data of the video etc. on better connections. As a fallback for non-supporting browsers, we could listen to canplaythrough event and use Promise.race() to timeout the source loading if the canplaythrough event doesn’t fire within 2 seconds.

    If you want to dive in a bit deeper, here are a couple of resources to get started:

  3. Consider making your components device memory-aware.
    Network connection gives us only one perspective at the context of the user though. Going further, you could also dynamically adjust resources based on available device memory, with the Device Memory API. navigator.deviceMemory returns how much RAM the device has in gigabytes, rounded down to the nearest power of two. The API also features a Client Hints Header, Device-Memory, that reports the same value.

    Bonus: Umar Hansa shows how to defer expensive scripts with dynamic imports to change the experience based on device memory, network connectivity and hardware concurrency .

The priority column in DevTools

The ‘Priority’ column in DevTools. Image credit: Ben Schwarz, The Critical Request
  1. Warm up the connection to speed up delivery.
    Use resource hints to save time on dns-prefetch (which performs a DNS lookup in the background), preconnect (which asks the browser to start the connection handshake (DNS, TCP, TLS) in the background), prefetch (which asks the browser to request a resource) and preload (which prefetches resources without executing them, among other things).

    Remember prerender? The resource hint used to prompt browser to build out the entire page in the background for next navigation. The implementations issues were quite problematic, ranging from a huge memory footprint and bandwidth usage to multiple registered analytics hits and ad impressions.

    Unsurprinsingly, it was deprecated, but the Chrome team has brought it back as NoState Prefetch mechanism. In fact, Chrome treats the prerender hint as a NoState Prefetch instead, so we can use it today. As Katie Hempenius explains in that article, “like prerendering, NoState Prefetch fetches resources in advance; but unlike prerendering, it does not execute JavaScript or render any part of the page in advance.” NoState Prefetch only uses ~45MiB of memory and subresources that are fetched will be fetched with an IDLE Net Priority. Since Chrome 69, NoState Prefetch adds the header Purpose: Prefetch to all requests in order to make them distinguishable from normal browsing.

    Most of the time these days, we’ll be using at least preconnect and dns-prefetch, and we’ll be cautious with using prefetch, preload and prerender; the former should only be used if you are confident about what assets the user will need next (for example, in a purchasing funnel).

    Note that even with preconnect and dns-prefetch, the browser has a limit on the number of hosts it will look up/connect to in parallel, so it’s a safe bet to order them based on priority (thanks Philip Tellis!).

    In fact, using resource hints is probably the easiest way to boost performance, and it works well indeed. When to use what? As Addy Osmani has explained, it’s a good idea to preload resources that we have high-confidence will be used on the current page. Prefetch resources likely to be used for future navigations across multiple navigation boundaries, e.g. Webpack bundles needed for pages the user hasn’t visited yet.

    Addy’s article on “Loading Priorities in Chrome” shows how exactly Chrome interprets resource hints, so once you’ve decided which assets are critical for rendering, you can assign high priority to them. To see how your requests are prioritized, you can enable a “priority” column in the Chrome DevTools network request table (as well as Safari).

    A break-down showing how different resources are prioritized in Blink as of Chrome 46 and beyond

    (Image credit: Pat Meenan) (Large preview)

    Since fonts usually are important assets on a page, sometimes it’s a good idea to request the browser to download critical fonts with preload. However, double check if it actually helps performance as there is a puzzle of priorities when preloading fonts: as preload is seen as high importance, it can leapfrog even more critical resources like critical CSS. (thanks, Barry!)

    You could also load JavaScript dynamically, effectively lazy-loading execution. Also, since <link rel="preload"> accepts a media attribute, you could choose to selectively prioritize resources based on @media query rules.

    A few gotchas to keep in mind: preload is good for moving the start download time of an asset closer to the initial request, but preloaded assets land in the memory cache which is tied to the page making the request. preload plays well with the HTTP cache: a network request is never sent if the item is already there in the HTTP cache.

    Hence, it’s useful for late-discovered resources, a hero image loaded via background-image, inlining critical CSS (or JavaScript) and pre-loading the rest of the CSS (or JavaScript). Also, a preload tag can initiate a preload only after the browser has received the HTML from the server and the lookahead parser has found the preload tag.

    Preloading via the HTTP header could be a bit faster since we don’t to wait for the browser to parse the HTML to start the request (it’s debated though). Early Hints will help even further, enabling preload to kick in even before the response headers for the HTML are sent (on the roadmap in Chromium, Firefox). Plus, Priority Hints will help us indicate loading priorities for scripts.

    Beware: if you’re using preload, as must be defined or nothing loads, plus preloaded fonts without the crossorigin attribute will double fetch.

  2. Use service workers for caching and network fallbacks.
    No performance optimization over a network can be faster than a locally stored cache on a user’s machine. If your website is running over HTTPS, use the “Pragmatist’s Guide to Service Workers” to cache static assets in a service worker cache and store offline fallbacks (or even offline pages) and retrieve them from the user’s machine, rather than going to the network. Also, check Jake’s Offline Cookbook and the free Udacity course “Offline Web Applications.”

    Browser support? As stated above, it’s widely supported and the fallback is the network anyway. Does it help boost performance? Oh yes, it does. And it’s getting better, e.g. with Background Fetch allowing background uploads/downloads from a service worker.

    There are a number of use cases for a service worker. For example, you could implement “Save for offline” feature, handle broken images, introduce messaging between tabs or provide different caching strategies based on request types. In general, a common reliable strategy is to store the app shell in the service worker’s cache along with a few critical pages, such as offline page, frontpage and anything else that might be important in your case.

    There are a few gotchas to keep in mind though. With a service worker in place, we need to beware range requests in Safari (if you are using Workbox for a service worker it has a range request module). If you ever stumbled upon DOMException: Quota exceeded. error in the browser console, then look into Gerardo’s article When 7KB equals 7MB.

    As Gerardo writes, “If you are building a progressive web app and are experiencing bloated cache storage when your service worker caches static assets served from CDNs, make sure the proper CORS response header exists for cross-origin resources, you do not cache opaque responses with your service worker unintentionally, you opt-in cross-origin image assets into CORS mode by adding the crossorigin attribute to the <img> tag.”

    A good starting point for using service workers would be Workbox, a set of service worker libraries built specifically for building progressive web apps.

  3. Are you using service workers on the CDN/Edge, e.g. for A/B testing?
    At this point, we are quite used to running service workers on the client, but with CDNs implementing them on the server, we could use them to tweak performance on the edge as well.

    For example, in A/B tests, when HTML needs to vary its content for different users, we could use Service Workers on the CDN servers to handle the logic. We could also stream HTML rewriting to speed up sites that use Google Fonts.

Timeseries of service worker installation. Only 0.44% of all desktop pages register a service worker, according to Web Almanac. (Large preview)
  1. Optimize rendering performance.
    Isolate expensive components with CSS containment — for example, to limit the scope of the browser’s styles, of layout and paint work for off-canvas navigation, or of third-party widgets. Make sure that there is no lag when scrolling the page or when an element is animated, and that you’re consistently hitting 60 frames per second. If that’s not possible, then at least making the frames per second consistent is preferable to a mixed range of 60 to 15. Use CSS’ will-change to inform the browser of which elements and properties will change.

    Also, measure runtime rendering performance (for example, in DevTools). To get started, check Paul Lewis’ free Udacity course on browser-rendering optimization and Georgy Marchuk’s article on Browser painting and considerations for web performance.

    If you want to dive deeper into the topic, Nolan Lawson has shared tricks to accurately measure layout performance in his article, and Jason Miller suggested alternative techniques, too. We also have a lil’ article by Sergey Chikuyonok on how to get GPU animation right.

    Note: changes to GPU-composited layers are the least expensive, so if you can get away by triggering only compositing via opacity and transform, you’ll be on the right track. Anna Migas has provided a lot of practical advice in her talk on Debugging UI Rendering Performance, too.

  2. Have you optimized rendering experience?
    While the sequence of how components appear on the page, and the strategy of how we serve assets to the browser matter, we shouldn’t underestimate the role of perceived performance, too. The concept deals with psychological aspects of waiting, basically keeping customers busy or engaged while something else is happening. That’s where perception management, preemptive start, early completion and tolerance management come into play.

    What does it all mean? While loading assets, we can try to always be one step ahead of the customer, so the experience feels swift while there is quite a lot happening in the background. To keep the customer engaged, we can test skeleton screens (implementation demo) instead of loading indicators, add transitions/animations and basically cheat the UX when there is nothing more to optimize. Beware though: skeleton screens should be tested before deploying as some tests showed that skeleton screens can perform the worst by all metrics.

  3. Do you prevent layout shifts and repaints?
    In the realm of perceived performance probably one of the more disruptive experiences is layout shifting, or reflows, caused by rescaled images and videos, web fonts, injected ads or late-discovered scripts that populate components with actual content. As a result, a customer might start reading an article just to be interrupted by a layout jump above the reading area. The experience is often abrupt and quite disorienting: and that’s probably a case of loading priorities that need to be reconsidered.

    The community has developed a couple of techniques and workarounds to avoid reflows. Always set width and height attributes on images, so modern browsers allocate the box and reserve the space by default (Firefox, Chrome).

    For both images or videos, we can use an SVG placeholder to reserve the display box in which the media will appear in. That means that the area will be reserved properly when you need to maintain its aspect ratio as well.

    Instead of lazy-loading images with external scripts, consider using native lazy-loading, or hybrid lazy-loading when we load an external script only if native lazy-loading isn’t supported.

    As mentioned above, always group web font repaints and transition from all fallback fonts to all web fonts at once — just make sure that that switch isn’t too abrupt, by adjusting line-height and spacing between the fonts with font-style-matcher. (Note that adjustments are complicated with complicated font stacks though.)

    To ensure that the impact of reflows is contained, measure the layout stability with the Layout Instability API. With it, you can calculate the Cumulative Layout Shift (CLS) score and include it as a requirement in your tests, so whenever a regression appears, you can track it and fix it.

    To calculate the layout shift score, the browser looks at the viewport size and the movement of unstable elements in the viewport between two rendered frames. Ideally, the score would be close to 0. There is a great guide by Milica Mihajlija and Philip Walton on what CLS is and how to measure it. It’s a good starting point to measure and maintain perceived performance and avoid disruption, especially for business-critical tasks.

    Bonus: if you want to reduce reflows and repaints, check Charis Theodoulou’s guide to Minimising DOM Reflow/Layout Thrashing and Paul Irish’s list of What forces layout / reflow as well as CSSTriggers.com, a reference table on CSS properties that trigger layout, paint and compositing.

Networking and HTTP/2

  1. Is OCSP stapling enabled?
    By enabling OCSP stapling on your server, you can speed up your TLS handshakes. The Online Certificate Status Protocol (OCSP) was created as an alternative to the Certificate Revocation List (CRL) protocol. Both protocols are used to check whether an SSL certificate has been revoked. However, the OCSP protocol does not require the browser to spend time downloading and then searching a list for certificate information, hence reducing the time required for a handshake.
  2. Have you adopted IPv6 yet?
    Because we’re running out of space with IPv4 and major mobile networks are adopting IPv6 rapidly (the US has reached a 50% IPv6 adoption threshold), it’s a good idea to update your DNS to IPv6 to stay bulletproof for the future. Just make sure that dual-stack support is provided across the network — it allows IPv6 and IPv4 to run simultaneously alongside each other. After all, IPv6 is not backwards-compatible. Also, studies show that IPv6 made those websites 10 to 15% faster due to neighbor discovery (NDP) and route optimization.
  3. Make sure all assets run over HTTP/2.
    With Google pushing towards a more secure HTTPS web over the last few years, a switch to HTTP/2 environment is definitely a good investment. In fact, according to Web Almanac, 54% of all requests are running over HTTP/2 already.

    It’s important to understand that HTTP/2 isn’t perfect and has prioritization issues, but it’s supported very well, it isn’t going anywhere; and, in most cases, you’re better off with it.

    If you’re still running on HTTP, the most time-consuming task will be to migrate to HTTPS first, and then adjust your build process to cater for HTTP/2 multiplexing and parallelization. For the rest of this article, I’ll assume that you’re either switching to or have already switched to HTTP/2.

54% of all requests are served over HTTP/2 in late 2019, according to Web Almanac — just 4 years after its formal standardization. (Image source: Web Almanac) (Large preview)
  1. Properly deploy HTTP/2.
    Again, serving assets over HTTP/2 can benefit from a partial overhaul of how you’ve been serving assets so far. You’ll need to find a fine balance between packaging modules and loading many small modules in parallel. At the end of the day, still the best request is no request, however, the goal is to find a fine balance between quick first delivery of assets and caching.

    On the one hand, you might want to avoid concatenating assets altogether, instead of breaking down your entire interface into many small modules, compressing them as a part of the build process and loading them in parallel. A change in one file won’t require the entire style sheet or JavaScript to be re-downloaded. It also minimizes parsing time and keeps the payloads of individual pages low.

    On the other hand, packaging still matters. By using many small scripts, overall compression will suffer. The compression of a large package will benefit from dictionary reuse, whereas small separate packages will not. There’s standard work to address that, but it’s far out for now. Secondly, browsers have not yet been optimized for such workflows. For example, Chrome will trigger inter-process communications (IPCs) linear to the number of resources, so including hundreds of resources will have browser runtime costs.

    Progressive CSS loading

    To achieve best results with HTTP/2, consider to load CSS progressively, as suggested by Chrome’s Jake Archibald.

    Still, you can try to load CSS progressively. In fact, in-body CSS no longer blocks rendering for Chrome. But there are some prioritization issues so it’s not as straightforward, but worth experimenting with.

    You could get away with HTTP/2 connection coalescing, which allows you to use domain sharding while benefiting from HTTP/2, but achieving this in practice is difficult, and in general, it’s not considered to be good practice. Also, HTTP/2 and Subresource Integrity don’t always get on.

    What to do? Well, if you’re running over HTTP/2, sending around 6–10 packages seems like a decent compromise (and isn’t too bad for legacy browsers). Experiment and measure to find the right balance for your website.

  2. Do your servers and CDNs support HTTP/2?
    Different servers and CDNs support HTTP/2 differently. Use Is TLS Fast Yet? to check your options, or quickly look up how your servers are performing and which features you can expect to be supported.

    Consult Pat Meenan’s incredible research on HTTP/2 priorities (video) and test server support for HTTP/2 prioritization. According to Pat, it’s recommended to enable BBR congestion control and set tcp_notsent_lowat to 16KB for HTTP/2 prioritization to work reliably on Linux 4.9 kernels and later (thanks, Yoav!). Andy Davies did a similar research for HTTP/2 prioritization across browsers, CDNs and Cloud Hosting Services.

    While on it, double check if your kernel supports TCP BBR and enable it if possible. It’s currently used on Google Cloud Platform, Amazon Cloudfront, Linux (e.g. Ubuntu).

  3. Do your servers and CDNs support HTTP over QUIC (HTTP/3)?
    If you feel adventurious or cutting-edge, you might want to check if your servers or CDNs support HTTP over QUIC (also known as HTTP/3). While HTTP/2 has brought significant improvements, it doesn’t perform particularly well in situations when network is slow or unreliable (significant packet loss).

    To address the issue, Google has been working on Google QUIC, which is the protocol used by Chrome for many Google services today. Google has then brought many of the learnings to IETF in 2015 which is being standardized now.

    QUIC and HTTP/3 are better and more bulletproof: with faster handshakes, better encryption, more reliable independent streams, more encrypted, and with 0-RTT if the client previously had a connection with the server. However, it’s quite CPU intensive (2-3x CPU usage for the same bandwidth), UDP stacks are unoptimized, and there are some unresolved issues with hardware and TLS layer.

    HTTP/3 is expected to ship early 2020 as a standard. Chrome and Safari confirmed that they have in-house implementations already, with HTTP/3 available in Chrome Canary and Firefox Nightly. Some CDNs support QUIC and HTTP/3 already. Neither Apache, nginx or IIS support it yet, but it might change in 2020.

Is TLS Fast Yet?

Is TLS Fast Yet? allows you to check your options for servers and CDNs when switching to HTTP/2. (Large preview)
  1. Is HPACK compression in use?
    If you’re using HTTP/2, double-check that your servers implement HPACK compression for HTTP response headers to reduce unnecessary overhead. Because HTTP/2 servers are relatively new, they may not fully support the specification, with HPACK being an example. H2spec is a great (if very technically detailed) tool to check that. HPACK’s compression algorithm is quite impressive, and it works.
  2. Make sure the security on your server is bulletproof.
    All browser implementations of HTTP/2 run over TLS, so you will probably want to avoid security warnings or some elements on your page not working. Double-check that your security headers are set properly, eliminate known vulnerabilities, and check your HTTPS setup. Also, make sure that all external plugins and tracking scripts are loaded via HTTPS, that cross-site scripting isn’t possible and that both HTTP Strict Transport Security headers and Content Security Policy headers are properly set.

Testing And Monitoring

  1. Have you optimized your auditing workflow?
    It might not sound like a big deal, but having the right settings in place at your fingertips might save you quite a bit of time in testing. Consider using Tim Kadlec’s Alfred Workflow for WebPageTest for submitting a test to the public instance of WebPageTest. In fact, WebPageTest has many obscure features, so take the time to learn how to read a WebPageTest Waterfall View chart and how to read a WebPageTest Connection View chart to diagnose and resolve performance issues faster.

    You could also drive WebPageTest from a Google Spreadsheet and incorporate accessibility, performance and SEO scores into your Travis setup with Lighthouse CI or straight into Webpack.

    And if you need to debug something quickly but your build process seems to be remarkably slow, keep in mind that “whitespace removal and symbol mangling accounts for 95% of the size reduction in minified code for most JavaScript — not elaborate code transforms. You can simply disable compression to speed up Uglify builds by 3 to 4 times.”

pull request checks review required

Integrating accessibility, performance and SEO scores into your Travis setup with Lighthouse CI will highlight the performance impact of a new feature to all contributing developers. (Image source) (Large preview)
  1. Have you tested in proxy browsers and legacy browsers?
    Testing in Chrome and Firefox is not enough. Look into how your website works in proxy browsers and legacy browsers. UC Browser and Opera Mini, for instance, have a significant market share in Asia (up to 35% in Asia). Measure average Internet speed in your countries of interest to avoid big surprises down the road. Test with network throttling, and emulate a high-DPI device. BrowserStack is fantastic, but test on real devices as well.
k6 allows you write unit tests-alike performance tests.
  1. Have you tested the impact on accessibility?
    When the browser starts to load a page, it builds a DOM, and if there is an assistive technology like a screen reader running, it also creates an accessibility tree. The screen reader then has to query the accessibility tree to retrieve the information and make it available to the user — sometimes by default, and sometimes on demand. And sometimes it takes time.

    When talking about fast Time to Interactive, usually we mean an indicator of how soon a user can interact with the page by clicking or tapping on links and buttons. The context is slightly different with screen readers. In that case, fast Time to Interactive means how much time passes by until the screen reader can announce navigation on a given page and a screen reader user can actually hit keyboard to interact.

    Léonie Watson has given an eye-opening talk on accessibility performance and specifically the impact slow loading has on screen reader announcement delays. Screen readers are used to fast-paced announcements and quick navigation, and therefore might potentially be even less patient than sighted users.

    Large pages and DOM manipulations with JavaScript will cause delays in screen reader announcements. A rather unexplored area that could use some attention and testing as screen readers are available on literally every platform (Jaws, NVDA, Voiceover, Narrator, Orca).

  2. Is continuous monitoring set up?
    Having a private instance of WebPagetest is always beneficial for quick and unlimited tests. However, a continuous monitoring tool — like Sitespeed, Calibre and SpeedCurve — with automatic alerts will give you a more detailed picture of your performance. Set your own user-timing marks to measure and monitor business-specific metrics. Also, consider adding automated performance regression alerts to monitor changes over time.

    Look into using RUM-solutions to monitor changes in performance over time. For automated unit-test-alike load testing tools, you can use k6 with its scripting API. Also, look into SpeedTracker, Lighthouse and Calibre.

Quick Wins

This list is quite comprehensive, and completing all of the optimizations might take quite a while. So, if you had just 1 hour to get significant improvements, what would you do? Let’s boil it all down to 15 low-hanging fruits. Obviously, before you start and once you finish, measure results, including start rendering time and Time To Interactive on a 3G and cable connection.

  1. Measure the real world experience and set appropriate goals. A good goal to aim for is Largest Contentful Paint < 1 s, a Speed Index < 3s, Time to Interactive < 5s on slow 3G, for repeat visits, TTI < 2s. Optimize for start rendering time and time-to-interactive.
  2. Prepare critical CSS for your main templates, and include it in the <head> of the page. For CSS/JS, operate within a critical file size budget of max. 170KB gzipped (0.7MB decompressed).
  3. Trim, optimize, defer and lazy-load as many scripts as possible, check lightweight alternatives and limit the impact of third-party scripts.
  4. Serve legacy code only to legacy browsers with <script type="module"> and module/nomodule pattern.
  5. Experiment with regrouping your CSS rules and test in-body CSS.
  6. Add resource hints to speed up delivery with faster dns-lookup, preconnect, prefetch, preload and prerender.
  7. Subset web fonts and load them asynchronously, and utilize font-display in CSS for fast first rendering.
  8. Optimize images with mozjpeg, guetzli, pingo and SVGOMG, and consider serving WebP with an image CDN.
  9. Check that HTTP cache headers and security headers are set properly.
  10. Enable Brotli compression on the server. (If that’s not possible, don’t forget to enable Gzip compression.)
  11. Enable TCP BBR congestion as long as your server is running on the Linux kernel version 4.9+.
  12. Enable OCSP stapling and IPv6 if possible.
  13. If HTTP/2 is available, enable HPACK compression and enable HTTP/3 if it’s available on CDNs.
  14. Cache assets such as fonts, styles, JavaScript and images in a service worker cache.
  15. Explore options to avoid rehydration, use progressive hydration and streaming server-side rendering for your SPA.

Download The Checklist (PDF, Apple Pages)

With this checklist in mind, you should be prepared for any kind of front-end performance project. Feel free to download the print-ready PDF of the checklist as well as an editable Apple Pages document to customize the checklist for your needs:

If you need alternatives, you can also check the front-end checklist by Dan Rublic, the “Designer’s Web Performance Checklist” by Jon Yablonski and the FrontendChecklist.

Off We Go!

Some of the optimizations might be beyond the scope of your work or budget or might just be overkill given the legacy code you have to deal with. That’s fine! Use this checklist as a general (and hopefully comprehensive) guide, and create your own list of issues that apply to your context. But most importantly, test and measure your own projects to identify issues before optimizing. Happy performance results in 2019, everyone!


A huge thanks to Guy Podjarny, Yoav Weiss, Addy Osmani, Artem Denysov, Denys Mishunov, Ilya Pukhalski, Jeremy Wagner, Colin Bendell, Mark Zeman, Patrick Meenan, Leonardo Losoviz, Andy Davies, Rachel Andrew, Anselm Hannemann, Barry Pollard, Patrick Hamann, Gideon Pyzer, Andy Davies, Maria Prosvernina, Tim Kadlec, Rey Bango, Matthias Ott, Peter Bowyer, Phil Walton, Mariana Peralta, Jean Pierre Vincent, Philipp Tellis, Ryan Townsend, Ingrid Bergman, Mohamed Hussain S. H., Jacob Groß, Tim Swalling, Bob Visser, Kev Adamson, Adir Amsalem, Aleksey Kulikov and Rodney Rehm for reviewing this article, as well as our fantastic community which has shared techniques and lessons learned from its work in performance optimization for everybody to use. You are truly smashing!


Smashing Editorial
(ra, il)

Source: Smashing Magazine, Front-End Performance Checklist 2020 [PDF, Apple Pages, MS Word]

Understanding CSS Grid: Creating A Grid Container

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Understanding CSS Grid: Creating A Grid Container

Understanding CSS Grid: Creating A Grid Container

Rachel Andrew



This is the start of a new series here at Smashing Magazine concentrating on CSS Grid Layout. While Grid has been available in browsers since 2017, many developers won’t have had a chance to use it on a project yet. There seem to be a lot of new properties and values associated with CSS Grid Layout. This can make it seem overwhelming. However, quite a lot of the specification details alternate ways to do things, meaning that you don’t have to learn the entire spec to get started. This series aims to take you from grid novice to expert — with lots of practical usage tips along the way.

This initial article will cover what happens when you create a grid container and the various properties that you can use on the parent element to control that grid. You will discover that there are several use cases that are fulfilled only with the properties that you apply to the grid container.

In this article, we will cover:

  • Creating a grid container with display: grid or display: inline-grid,
  • Setting up columns and rows with grid-template-columns and grid-template-rows,
  • Controlling the size of implicit tracks with grid-auto-columns and grid-auto-rows.

Overflow And Data Loss In CSS

CSS is designed to keep your content readable. Let’s explore situations in which you might encounter overflow in your web designs and how CSS has evolved to create better ways to manage and design around unknown amounts of content. Read article →

Creating A Grid Container

Grid, like Flexbox, is a value of the CSS display property. Therefore to tell the browser that you want to use grid layout you use display: grid. Having done this, the browser will give you a block-level box on the element with display: grid and any direct children will start to participate in a grid formatting context. This means they behave like grid items, rather than normal block and inline elements.

However, you may not immediately see a difference on your page. As you haven’t created any rows or columns, you have a one-column grid. Enough rows are being generated to hold all of your direct children, and they are displaying one after the other in that single column. Visually they look just like block elements.

You will see a difference if you had any string of text, not wrapped in an element, and a direct child of the grid container, as the string will be wrapped in an anonymous element and become a grid item. Any element which is normally an inline element, such as a span, will also become a grid item once its parent is a grid container.

The example below has two block-level elements, plus a string of text with a span in the middle of the string. We end up with five grid items:

  • The two div elements,
  • The string of text before the span,
  • The span,
  • The string of text after the span.

See the Pen Grid Container: Direct children and strings of text become grid items by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: Direct children and strings of text become grid items by Rachel Andrew (@rachelandrew) on CodePen.

If you inspect the grid using the Firefox Grid Inspector, you can see the five-row tracks that have been created for the items.

A single column grid with five rows

The Grid Inspector is useful to help you see how many rows have been created

You can also create an inline grid by using display: inline-grid; in this case, your grid container becomes an inline-level box. However, the direct children are still grid items and behave in the same way as grid items inside a block-level box (it is only the outer display type). That is why the grid container behaves the way it does above when it is alongside other boxes on the page.

This next example has a grid followed by a string of text, as this is an inline-level grid, the text can display alongside it. Inline-level things do not stretch to take up all the space in the inline dimension in that way that block-level things do.

See the Pen Grid Container: inline-grid by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: inline-grid by Rachel Andrew (@rachelandrew) on CodePen.

Note: In the future, we will be able to better describe our layout by using display: block grid in order to create our block-level container, and display: inline grid to create an inline-level container. You can read about this change to the display specification in my article, “Digging Into The DIsplay Property: The Two Values Of Display”.

Columns And Rows

To get something that looks like a grid, we will need to add columns and rows. These are created using the grid-template-columns and grid-template-rows properties. These properties are defined in the spec as accepting a value called a track-list.

These properties specify, as a space-separated track list, the line names and track sizing functions of the grid. The grid-template-columns property specifies the track list for the grid’s columns, while grid-template-rows specifies the track list for the grid’s rows.

Some valid track-list values are as follows:

grid-template-columns: 100px 100px 200px; Creates a three-column grid: The first column is 100px, the second 100px, the third 200px.
grid-template-columns: min-content max-content fit-content(10em) Creates a three-column grid: The first column is the min-content size for that track, the second the max-content size. The third is either max-content unless the content is larger than 10em, in which case it is clamped to 10em.
grid-template-columns: 1fr 1fr 1fr; Creates a three-column grid using the fr unit. The available space in the grid container is divided into three and shared between the three columns.
grid-template-columns: repeat(2, 10em 1fr); Creates a four-column grid with a repeating pattern of 10em 1fr 10em 1fr as the track-list in the repeat statement is repeated twice.
grid-template-columns: repeat(auto-fill, 200px); Fills the container with as many 200px columns as will fit leaving a gap at the end if there is spare space.
grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); Fills the container with as many 200px columns as will fit then distributes the remaining space equally between the created columns.
grid-template-columns: [full-start] 1fr [content-start] 3fr [content-end] 1fr [full-end]; Creates a three-column grid: The first and third columns have 1 part each of the available space while the middle column has 3 parts. The lines are named by putting line names in square brackets.

As you can see there are many ways to create a track listing! Let’s have a look at exactly how these all work, with a few tips in terms of why you might use each one.

Using Length Units

You can use any length units, or a percentage to create your tracks. If the size of the tracks adds up to less than is available in the grid container, then by default the tracks will line up at the start of the container and the spare space will go to the end. This is because the default value of align-content and justify-content is start. You can space out the grid tracks, or move them to the end of the container using the alignment properties, which I explain in detail in my article “How To Align Things In CSS”.

See the Pen Grid Container: length units by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: length units by Rachel Andrew (@rachelandrew) on CodePen.

You can also use the keywords min-content, max-content and fit-content(). Using min-content will give you a track that is as small as it can be without causing overflow. Therefore, when used as a column size, the content will softly wrap wherever possible. The track becoming the size of the longest word in the column or largest fixed-size element.

Using max-content will cause the content to not do any soft-wrapping at all. In a column, any string of text will unwrap which may cause overflow.

The fit-content keyword can only be used by passing in a value. That value becomes the max that this track will grow to. Therefore, the track will act like max-content with the content unwrapping and stretching out until it hits the value you passed in. At that point, it will start wrapping as normal. So your track may be smaller than the value you pass in, but never larger.

See the Pen Grid Container: min-content, max-content, fit-content() by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: min-content, max-content, fit-content() by Rachel Andrew (@rachelandrew) on CodePen.

You can find out more about sizing in Grid and other layout methods in my article “How Big Is That Box? Understanding Sizing In CSS Layout”.

If you end up with tracks that take up more space than you have in your container, they will overflow. If you use percentages then, as with percentage-based float or flex layouts, you will need to take care that the total percentage is not more than 100% if you want to avoid overflow.

The fr Unit

Grid Layout includes a method that can save you calculating percentages for yourself — track sizing with the fr unit. This unit isn’t a length, and therefore can’t be combined with calc(); it is a flex unit and represents the available space in the grid container.

This means that with a track-list of 1fr 1fr 1fr; the available space is divided into three and shared evenly between the tracks. With a track-list of 2fr 1fr 1fr, the available space is divided into four and two parts are given to track one — one part each to tracks two and three.

See the Pen Grid Container: fr by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: fr by Rachel Andrew (@rachelandrew) on CodePen.

Something to watch out for is that what is being shared out by default is available space which is not the total space in the container. If any of your tracks contain a fixed-size element or a long word that can’t be wrapped, this will be laid out before the space is shared out.

In the next example, I removed the spaces between the words of ItemThree. This made a long unbreakable string so space distribution happens after the layout of that item has been accounted for.

See the Pen Grid Container: fr with larger content by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: fr with larger content by Rachel Andrew (@rachelandrew) on CodePen.

You can mix the fr unit with fixed length tracks, and this is where it becomes very useful. For example, you could have a component with two fixed-sized columns and a center area that stretches:

See the Pen Grid Container: mixing fr units and fixed-size tracks by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: mixing fr units and fixed-size tracks by Rachel Andrew (@rachelandrew) on CodePen.

You can have a component with one track set to fit-content(300px) and the other to 1fr. This makes for a component that can have something smaller than 300px in the first track, in which case it only takes the space it needs and the fr unit expands to take up the rest of the space.

If you add something larger (such as an image with max-width: 100%), the first track will stop growing at 300px and the fr unit takes the rest of the space. Mixing the fr unit with fit-content is a way to make some very flexible components for your site.

See the Pen Grid Container: mixing fr and fit-content() by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: mixing fr and fit-content() by Rachel Andrew (@rachelandrew) on CodePen.

The repeat() Function

Using repeat() in your track-list can save typing out the same value or values over and over again. For example the following two lines are the same:

grid-template-columns: 1fr 1fr 1fr 1fr 1fr 1fr 1fr 1fr 1fr 1fr 1fr 1fr;
grid-template-columns: repeat(12, 1fr);

When using repeat() the value before the column is the number of times to repeat the track-list that comes after the comma. That track-list can be multiple values. This means you can repeat a pattern of tracks.

You can use the repeat() function for part of a track-list. For example, the following line would give you a 1fr track, 3 200px tracks, and a final 1fr track.

grid-template-columns: 1fr repeat(3,200px) 1fr

In addition to a number before the comma to indicate a fixed number of times to repeat the pattern, you can also use the keywords auto-fill or auto-fit. Using one of these keywords means that instead of a fixed number of tracks, your grid container will be filled with as many tracks as will fit.

See the Pen Grid Container: auto-fill by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: auto-fill by Rachel Andrew (@rachelandrew) on CodePen.

Using a fixed-length unit means that, unless the container is able to be exactly divided by that size, you will end up with some spare space remaining. In the example above my container is 500px wide, so I get two 200px tracks plus space at the end.

We can use another grid function to make the value a minimum, with any spare space distributed across all of the tracks. The minmax() function takes a minimum and a maximum size. With a minimum of 200px and a max of 1fr, we get as many 200px tracks as will fit and because the max is 1fr, which we already know will share out the space evenly, the extra is distributed across the tracks.

See the Pen Grid Container: auto-fill and minmax() by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: auto-fill and minmax() by Rachel Andrew (@rachelandrew) on CodePen.

I mentioned there are two possible keywords: auto-fill and auto-fit. If you have enough content to fill the first row of cells, then these will behave in exactly the same way. If, however, you do not (e.g. if we remove all but one item inside the container above), then they behave differently.

Using auto-fill will maintain the available track sizing even if there is no content to go into it.

See the Pen Grid Container: auto-fill and minmax() with one item by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: auto-fill and minmax() with one item by Rachel Andrew (@rachelandrew) on CodePen.

If, instead, you use auto-fit, the empty tracks will be collapsed:

See the Pen Grid Container: auto-fit and minmax() with one item by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: auto-fit and minmax() with one item by Rachel Andrew (@rachelandrew) on CodePen.

By using the Firefox Grid Inspector, you can see that the tracks are still there, but have been collapsed to zero. The end line of our grid is still line 3 as we can fit two tracks.

A single grid item fills the container, the grid inspector highlights the column lines

The track is still there but collapsed

Named Lines

My final example above used the named lines approach. When using Grid. you always have line numbers, however, you can also name the lines. Lines are named inside square brackets. You can have multiple names for one line; in that case, a space separates them. For example, in the following track-list, all of my lines have two names.

grid-template-columns: [main-start sidebar-start] 1fr [sidebar-end content-start] 4fr [content-end main-end]

You can name your lines anything that you like, except the word span as that is a reserved word due to being used when placing items on the grid.

Note: In the next article in this series, I’ll be talking more about line-based placement and how named lines are used. In the meantime, read my article on “Naming Things in CSS Grid Layout” to help you learn more on the topic.

The Explicit vs The Implicit Grid

When creating a grid using grid-template-columns and grid-template-rows with a track-list, you are creating what is referred to as the explicit grid. This is the grid you have defined which has the sizing you have chosen for each track.

If you have more items than will fit, or place an item so it falls outside of the bounds of the grid you have created, Grid will create tracks in the implicit grid. These implicit tracks will be auto-sized by default. We saw this implicit grid in action when I declared display: grid on the parent element and grid created rows, one for each item. I didn’t define these rows, but as there were grid items, the row tracks were created to give them somewhere to go.

You can set a size for implicit rows or columns by using the grid-auto-rows or grid-auto-columns properties. These properties take a track-listing, so if you want all implicit columns to be at least 200 pixels tall but grow if there is more content, you could use the following:

grid-auto-rows: minmax(200px, auto)

If you want the first implicit row to be auto-sized, and the second to be min-content sized, and so on (until all of the grid items have been accommodated), you can pass in multiple values:

grid-auto-rows: auto 100px

See the Pen Grid Container: grid-auto-rows by Rachel Andrew (@rachelandrew) on CodePen.

See the Pen Grid Container: grid-auto-rows by Rachel Andrew (@rachelandrew) on CodePen.

Using A Grid With Auto-Placement

Creating a grid (and allowing the browser to auto-place items) gets you a long way in terms of the useful patterns you can achieve. We have not yet looked at placing items on the grid, but many layouts that make use of Grid don’t do any placement. They simply rely on placing the items in source order — one in each grid cell.

If you are new to CSS Grid, then playing with different track sizes and seeing how the items place themselves into the cells you create is a great way to start.

Smashing Editorial
(il)

Source: Smashing Magazine, Understanding CSS Grid: Creating A Grid Container

Collective #577

dreamt up by webguru in Uncategorized | Comments Off on Collective #577




Collective item image

Mix and Jam

André Cardoso started a gamedev journey and shares it by creating videos and making all of the code available.

Check it out















Collective item image

Convert2Svg

A free and open-source tool to easily transform any image or photo into a multi-colored SVG file. Created by Vincent Will with Next.js.

Check it out


C577_Botland

Bot Land

Bot Land is an automated strategy game where you have to create bots, write scripts, and battle other players.

Check it out




Collective item image

From Our Blog

Case Study: Akaru 2019

In this creative breakdown you will learn how the signature WebGL oil effect of the new Akaru website was created.

Read it


Collective #577 was written by Pedro Botelho and published on Codrops.


Source: Codrops, Collective #577

How To Decide Which PWA Elements Should Stick

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How To Decide Which PWA Elements Should Stick

How To Decide Which PWA Elements Should Stick

Suzanne Scacca



As the number of website visitors and shoppers grows on mobile, it’s important to consider how small additions to your design will encourage them to do more than just research and browse. One of the elements I think mobile designers — for PWAs and mobile websites — need to do more with is the sticky bar.

What exactly do I mean by “more”? Well, I mean using the fixed navigation bar at the top or bottom of a mobile site for more than just navigation or branding.

Today, I’m going to show you some creative uses for sticky elements in mobile design, so you can help more of your visitors to take action.

Sticky Element Inspiration For Mobile Design

Think about the main challenge we face when it comes to mobile. While users are more than willing to take their first steps on a website or PWA from their mobile devices, conversion often happens on desktop (if they remember to do it at all).

When used properly, fixed elements can encourage more mobile visitors to take action right where they are. And this works for all kinds of websites.

1. Make the Top Sticky Bar Useful

The sticky bar at the top of your mobile site shouldn’t just be there for branding.

That said, I get that it can be tricky using that space when the logo may end up comprising a good chunk of that space. But if you design it thin enough, you can stack another banner beside it. Just make sure it’s useful.

The Lancome PWA is an interesting example because it simultaneously does this well and poorly:

Lancome sticky bars

Lancome has three sticky bars at the top of its PWA. (Source: Lancome) (Large preview)

There are three sticky bars at the top of the PWA:

  • A banner promoting a special offer,
  • A standard navigation bar,
  • A secondary navigation bar with shop categories.

The two navigation bars are great. Together, they don’t take up too much space and they make it much easier for users to find what they’re looking for and to complete their purchases. However, that promotional banner is not very well executed.

For starters, it’s too big and demands too much attention. Secondly, there’s no way to dismiss the message. It just stays there, stuck to the top of the PWA, no matter where the visitor goes.

If you’re going to use a sticky bar to promote an offer — no matter its size — give your users the option to move it out of the way if it’s irrelevant or if they’ve already collected the pertinent details from it.

George.com is another e-commerce web app that takes advantage of the top sticky bar. This one, however, doesn’t waste the space with distracting elements.

George.com sticky navigation and search

George.com uses a standard navigation bar and sticky search bar on its PWA. (Source: George.com) (Large preview)

On the home page, George.com attaches a sticky and voice-enabled search bar to the top of the page. This is great as it caters to a number of visitor types:

  • Visitors that prefer to use the standard navigation from the menu.
  • Visitors that prefer to type a quick search to the exact item they need.
  • Visitors that want to use their voice to search for something.

It checks off all the boxes.

In addition to providing a great search experience for its store, George.com also customizes this sticky element as visitors go deeper into the site:

George.com sticky Sort and Filter

George.com provides shoppers with a sticky Sort and Filter bar. (Source: George.com) (Large preview)

As shoppers peruse product pages, the sticky search bar becomes a Sort and Filter bar that follows them down the page. For big online stores, this is a useful tool so mobile users don’t have to scroll all the way to the top to adjust their search results.

The top sticky bar isn’t just useful for e-commerce stores as you’ll see in the rest of the examples in this article. However, when it comes to mobile, there’s a greater opportunity for e-commerce sites to pack extra value into this space, so take advantage of it.

2. Add a Bottom Navigation Bar with Quick-Tap Actions

Okay, so we’ve established what makes for a good sticky top bar. But what about a bottom bar? Is it even necessary?

One of the benefits of designing a PWA instead of a mobile site is that we can give it the top and bottom wrapper. But it’s not always needed. I’d say as a general rule of thumb to include a bottom bar when there are commonly used actions you want users to have easy access to.

Let’s start with an example that’s a mix of the good and the eh: Twitter.

Twitter sticky bottom navigation bar

Twitter places its sticky navigation bar on the bottom of the PWA. (Source: Twitter) (Large preview)

Twitter has chosen a different placement for its navigation bar. While the sticky bar at the top provides a place to access user settings, the bottom is for:

  • Visiting one’s news feed;
  • Searching for posts, people, hashtags, etc.;
  • Checking on notifications and direct messages.

For a social media app, this design makes a lot of sense. It’s not as though users are going to spend much time updating their settings, so why not put it out of the thumb zone and keep the regularly used elements within reach?

The issue I take with Twitter’s sticky elements is the click-to-tweet button (the big blue button in the bottom-left). While it’s not high enough to cover content being read at the top of the page, it does cover part of it down below.

It’s awfully reminiscent of those floating social icons that used to cover content on mobile. You don’t really see that anymore and I think it was for that exact reason.

If you’re thinking about adding a free-standing sticky element of your own to your site, make sure it doesn’t cover any content. Twitter may be able to get away with it, but your brand might not.

As for other examples of bottom bars, let’s turn our attention to the Weather Channel PWA:

Weather Channel PWA sticky bars

The Weather Channel PWA uses both a sticky top and bottom bar. (Source: Weather Channel) (Large preview)

What’s nice about the top bar, in particular, is that it prioritizes the user experience instead of its own branding. Once a visitor enters their location, the rest of the site’s content is personalized, which is great.

As for the bottom navigation, Weather Channel has done a really nice job with this. Similar to how Twitter places commonly used buttons in its bottom bar, the same idea is present here. After all, it’s not as though Weather Channel visitors are coming to the site to read about Dover Federal Credit Union. They want to get precise predictions for upcoming weather.

Now, the two examples above show you how to use the bottom navigation bar as a permanent fixture on a mobile site. But you can also use it as a custom feature on your internal pages as job search site The Muse does:

The Muse bottom sticky bar

The Muse uses a sticky bar to shortcut various actions visitors might want to take. (Source: The Muse) (Large preview)

This bottom sticky bar appears only on job listings pages. Notice how it doesn’t just say “Apply”.

I’m willing to bet The Muse designer spent time studying its user journey and how frequently job seekers actually apply for a position the first time they see it. By including “Email Myself” and “Save” buttons in this action bar, it addresses the fact that job seekers might need time to mull the decision over or to prepare the application before filling it out.

So, while you can certainly use a sticky bottom bar as a type of secondary navigation for commonly-clicked pages, I’d also suggest looking at it the way The Muse has: by designing a sticky bar that’s tailor-made for your own user’s journey.

3. Simplify Order Customization with Sticky Elements

Remember the days when you’d have to call up your local restaurant to place an order for delivery or when, gulp, you had to actually visit a store to buy something? Online ordering is an amazing thing — but it could be even better if we set up our mobile sites and PWAs the right way for it.

Again, I want to start with an example that kinda gets it right.

This is the PWA for MINI USA:

MINI USA PWA car customization

Users customize their Mini Cooper on a page with an oversized sticky element. (Source: MINI USA) (Large preview)

This is what users go through when they want to customize their car before purchasing. Looking at it from this screenshot, it looks nice. You can see the car in its customized state along with the updated price.

However, that entire section — down to the “Review” and “Save” buttons — is fixed. That means that all customization takes place on about a third to a quarter of the screen down below. It’s not an easy customization experience, to say the least.

While the customization screen needs some work, it’s the final Review screen that is done nicely:

MINI USA sticky action bar

The MINI USA Review page adds a sticky action bar to the bottom. (Source: MINI USA) (Large preview)

Here the top bar has gone back to a normal size while a new action bar has been added to the bottom. This is similar to what The Muse does to streamline the next steps with job applicants. In this case, MINI gives potential customers the ability to choose one of a number of options, even if they don’t lead to an immediate sale.

There are other types of PWAs and mobile sites that can and should simplify the online ordering process. Like MINI, Uber Eats uses custom sticky elements to help users put together their orders.

Uber Eats sticky menu

Uber Eats includes a top menu navigation bar in its PWA. (Source: Uber Eats) (Large preview)

When a user has selected a restaurant to order from, a sticky menu bar appears at the top of the page. This is especially useful for lengthy menus as well as to help users quickly navigate to the kind of food they’re jonesing for.

Assuming the user has found an item they want, the next page removes the top sticky bar and adds an “Add to Order” button/bar instead.

Uber Eats “Add to Order” button

Uber Eats places an “Add to Order” button at the bottom of its web app. (Source: Uber Eats) (Large preview)

This way, the distraction of other menu categories is gone and now the user only has to focus on customizing the selected item before placing it in the cart.

Again, what this comes down to is being able to predict your users’ steps before they even get there. You can use either the top or bottom navigation to aid in this process, but it’s best to place initial steps in a sticky top bar and later steps at the bottom as they near conversion.

4. Display “Sidebar” Widgets On Digital Publications

Without a sidebar on mobile, you might try to tuck the widgets that would otherwise be there at the bottom of your content. But unless you know that your content is going to be read all the way through and that visitors will keep scrolling for more, there’s no guarantee they’ll see anything you put down there.

So, when it makes sense to do so, use sticky bars to add only the most essential sidebar-esque content.

Let’s take Inc., for example.

nc.’s sticky bars and elements

Inc.’s PWA comes with a sticky subscription bar, banner ad and secondary hamburger menu. (Source: Inc.) (Large preview)

There are three sticky elements that appear around Inc.’s articles:

  • A subscription form (which can be dismissed),
  • A banner ad (which cannot),
  • A floating hamburger menu.

The first two elements are fine since at least one of them is dismissible. However, the floating hamburger menu is problematic since it covers part of the content. Considering this is a content-centric site, it’s probably not a good idea to cover any part of the page.

The only way we might be able to excuse the placement of this fixed element is if it were to add extra value to the content. However, all it does is give readers more articles to read:

Inc. floating hamburger menu

Inc.’s floating hamburger menu contains more articles to read. (Source: Inc.) (Large preview)

The goal on any content website is to get visitors to actually read the content. But if you’re presenting them with other options straight away, you’re only giving them more content to get distracted by.

The concept of this floating menu is a good one, but the execution isn’t great. I’d recommend displaying it as visitors get at least 75% of the way down the page. That way, it only comes into view when they should be looking for related content to read.

As for publications that get the sticky elements right, look for ones that keep it simple.

The New Yorker, for instance, does a nice job of using the sticky navigation bar and a darker, less distracting bottom bar to promote its subscriptions:

The New Yorker sticky bars

The New Yorker uses sticky bars to promote its paid subscriptions. (Source: The New Yorker) (Large preview)

If it’s important to you to get subscribers for your publication — especially paid ones — this is a good way to make use of the fixed bars on mobile.

If, instead, you’re more focused on getting the word out about your content, then a sticky bar like the one The Billings Gazette uses would be better:

The Billings Gazette sticky social bar

The Billings Gazette prioritizes sharing over subscribing of its content. (Source: The Billings Gazette) (Large preview)

This is really well done. Social media sharing options are limited to the ones that make the most sense for mobile users. The same goes for the other share options here: WhatsApp, text, and email. When clicked, the corresponding app opens, so readers don’t have to use their browser sharing options or copy-and-paste the link.

In all honesty, I’m not sure it should be an either/or. I think you could use the top bar to promote your subscription so long as it’s easy to dismiss. Then, the bottom bar could be used for sharing links. Just make sure one of the bars moves out of the way so you can maximize the reading space.

Wrapping Up

Bottom line? It’s time to start using your sticky mobile elements for more than just storage of a logo, hamburger menu or search bar.

As we’ve seen here today, the key is to figure out what your users need most from you. Then, use your sticky elements to build a shortcut that makes a difference in their experience.

Smashing Editorial
(ra, yk, il)

Source: Smashing Magazine, How To Decide Which PWA Elements Should Stick

2019: A Smashing Year In Review

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2019: A Smashing Year In Review

2019: A Smashing Year In Review

Rachel Andrew



2019 has been a productive — sometimes challenging — but ultimately very successful year for the Smashing Team. In this annual round-up, I’d like to share some of my thoughts and those of some of the Smashing team, as we look back on the past year as well as look ahead and forward to 2020.

Travel And Friendships

As always, my 2019 has involved a lot of travel. In addition to my conference speaking engagements and travel to W3C meetings, I attended all four of our Smashing conferences; I ran CSS Layout workshops in Toronto, New York and San Francisco. The conferences are a time when most of the team is together in person.

An illustration of Topple the Smashing Mascot cat networking while sitting in a comfortable couch with its laptop placed on its lap holding a cup of coffee or tea, who knowsThe home of Smashing is in Freiburg, Germany, and before SmashingConf Freiburg, we held a big team meeting, with almost everyone who is involved with Smashing able to take part. There have been many changes in the Smashing Team this year, and that meeting in Freiburg was a chance for us all to come together; I believe that it was one of the most valuable things we have done this year.

There are many challenges in doing all of the things we do as a small (mainly part-time and remote) team. However, if we keep talking and keep the Smashing community at the heart of everything we do, the past year demonstrates that we can achieve amazing things!

The Conferences

The SmashingConf team of Amanda Annandale, Charis Rooda and Mariona Jones are a force of nature. They seem to achieve the impossible and (as Charis told me) still have time to enjoy the surroundings of the places they visit.

The team in front of the Toronto sign

The SmashingConf team in Toronto

I’m always blown away when I walk into the venue and see what has been achieved — even before the event starts. Artwork created by the talented Ricardo Gimenes is everywhere — such as the movie posters from Toronto, and the artwork in the theater we use as a venue in New York.

Movie posters features Topple the Smashing cat

Our movie posters in Toronto (Photo credit Marc Thiele)

A large theatre sign featuring Topple the cat

The signage in the theater in New York (Photo credit Drew McLellan)

One of my favorite things to do at the conferences is to lead the Smashing Run, which we normally manage to do on both conference days. This is becoming quite a fixture, with several attendees and speakers running and chatting for half an hour before breakfast. I’m already looking forward to our inaugural run in Austin in 2020, though it may be a bit of a warm one!

I sometimes help the conference team out when words need writing or editing, and sometimes when the legality of balloons is called into question. As Amanda Annandale (Senior Event Manager) remembers:

“September marked my third year at Smashing, and while it provided a whole new set of challenges, it also provided a huge sense of accomplishments. The conference team sat down at the end of 2018 and was able to make some big plans for the future.

“It’s been amazing to see these plans (from organization to side-events to new locations), and our team, come together. But, new tasks can bring about some hilarious roadblocks. Smashing is on a long and necessary quest to reduce our carbon footprint. BUT, Vitaly is rather partial to balloons.

“For those who may not know (because Rachel Andrew and I were shocked to learn), foil balloons are heavily regulated in the state of California. This (we discovered while spending a disproportionate time researching eco-balloons over plastic balloons) is obviously bad for the environment. We’ve never been so happy to find a company making fully eco-friendly balloons, that are fully biodegradable in a very short amount of time! This experience definitely strengthened our resolve.

“We are now working with a company out of Austin to improve our printing processes to be more eco-friendly, and working with each of our caterers to reduce our waste. We still have a way to go, but we’re aiming for a Smashing impact in 2020!”

Conference attendees standing up throwing balloons

The (eco-friendly) balloons are deployed in San Francisco (Photo credit Marc Thiele)

Conferences are expensive to produce and we are fortunate to have some wonderful partners who help us to create these events. They are looked after by our partnerships manager Mariona Jones, who has been joined this year by Esther Fernández. Between them, they are working to bring together all of the Smashing properties in order to create new partnership opportunities. Mariona told me,

“The most exciting moment this year has been to be able to create together with the whole team the Smashing Media platform bringing together events, magazine, publishing house, membership and Smashing TV. The highlight of the year is undoubtedly the birth of the partnerships and data office and the addition to the Smashing Family of my dear colleague Esther.”

Esther adds,

“Joining the Smashing team has been one of the highlights of the year. It’s been a pleasure to enter this community and to make the Smashing conferences happen.”

I’m looking forward to working together with Mariona and Esther this year as we open up new opportunities for partnerships that cross the boundaries of the different parts of the platform!

Smashing Magazine

Topple the Cat wearing its Thinking HatThe heart of what I do at Smashing is the online magazine; as Editor in Chief, my role here is to try to bring you web design and development content that will inform you, help with your day-to-day work, and also make you think. We publish almost every weekday, so always have a large list of articles moving through the writing, editing and publishing process.

Looking through our analytics, I pulled up a list of the most popular articles published in the last year. The range of topics making it to the top may surprise you, and demonstrate the wide range of subjects we cover here. We have the Front-End Performance Checklist, an article comparing Sketch, Figma, and Adobe XD, and two articles about designing tables: Table Design Patterns On The Web and How To Architect A Complex Web Table. HTML and CSS are always popular with How To Align Things In CSS, How To Learn CSS and HTML5 Input Types: Where Are They Now? —all getting a top spot. They are joined by Styling An Angular Application With Bootstrap and Using Vue.js To Create An Interactive Weather Dashboard. That’s quite the range of subject matter!

Covering such a broad spectrum of web design and development is certainly a challenge and one I couldn’t do alone. My subject editors Alma Hoffmann, Chui Chui Tan, Drew McLellan and Michel Bozgounov bring their expertise to the topics they help curate. Copy editors Andrew Lobo and Owen Gregory help preserve the tone of voice of our authors while ensuring the content is easy to understand for an international audience. Cosima Mielke ensures that the newsletter is well researched along with many other roles (including eBook production), and Yana Kirilenko does a great job of getting articles from Google Docs, Dropbox Paper and various Markdown apps into the CMS. Senior editor Iris Ljesnjanin does an amazing job of keeping everything on track, fielding the email, hitting publish on most of the pieces, and making sure that we are all using smashingly correct punctuation! I am very grateful for all of their work.

Vitaly and I are well-known faces in the web community, however, there is a whole cast of folk working behind the scenes to keep the magazine running successfully. I don’t say thank you enough, but I sincerely appreciate all the work that goes into the magazine across the team.

Smashing Magazine turned 13 this year to which I shared personal stories from the team — you can read more about the people behind the Smashing scenes over here.

This year, I’ve tried to bring the various facets of the business into the magazine. For example, each conference results in a set of high-quality videos of the presentations which was hidden away on Vimeo. This year, I’ve published a write-up of each event, listing all of the videos. I hope that this means more people can benefit from the wisdom of our speakers and also shows the brilliant work the conference team does in curating and putting on these events.

Something that I really enjoy is to publish articles by folks who have never written for a large publication before and to help their articles go through the process. Earlier this year, I wrote an article on Pitching Your Writing To Publications. If your 2020 goals include writing for Smashing Magazine, drop us a line with an outline of your idea. We would love to work with you!

Smashing Books And Our First Print Magazine

In 2019, we published two printed books, plus our very first print magazine. Art Direction For The Web was published in the spring, and at the end of the year, we began shipping Inclusive Components.

In the middle of the launch of Inclusive Components, we welcomed a new team member, Ari Stiles. She told me,

“It was challenging and fun to start working on the Smashing Library right after Heydon’s book was released, when promotion was already in full swing. A bit like stepping in front of a firehose — but in a good way! It helps that Inclusive Components is a well-written, timely book. I love helping people discover new and helpful resources like this one, and I’m excited about all of our new books for 2020.”

Topple the Cat presenting the Smashing Print coverSelecting a topic for our first print magazine was tricky. We wanted these magazines to be a snapshot of the industry at a certain time, but also to have a longer shelf life than tutorials on topics that will be out of date in a few months. Ultimately, for issue one, we chose a subject that was at the forefront of many minds in 2019 — that of ethics and privacy. The collection of essays I commissioned is designed to make you think, and we still have a few print copies and the digital version, if you would like to read them.

🎉 We’re currently in the planning stage for issue 2 — watch this space!

All of our books come with an eBook version, and one of Cosima Mielke’s many roles is to produce this version from the final manuscript. Memories of working on these projects were her response when I asked her about her 2019:

“As an eBook Producer, the moment when you’re being handed over the proofread manuscript to get started with eBook production is always a special moment. So many people — reviewers, proofreaders, and most importantly, the authors themselves, have already invested so much time and efforts into the manuscript, and now it’s your turn to put it into its final shape: the eBook that people are going to download and read.

“My personal highlight (and biggest challenge) this year was to turn the monumental opus that Andy provided with “Art Direction for the Web” into an eBook. The assets included almost 600 images — most of the designs created by Andy from scratch — and turning these into an eBook that does justice to the author’s meticulous work, provides a pleasant reading experience (given the rather limited possibilities that eBook reading devices usually offer), and has a reasonable file size at the same time, was quite a balancing act. Looking back, it was the most challenging eBook I have worked on to date — and, naturally, these kinds of projects make you feel proudest once you’ve accomplished them. I’m already curious to find out what 2020 will bring.”

The Smashing Podcast

Smashing Podcast moderated by Drew McLellanFor the first time this year, Smashing Magazine has a podcast. Hosted by Drew McLellan, this bi-weekly show interviews someone from the world of web design and development. We hope to bring you some well-known names, but also speak to folks doing interesting things across the industry.

In addition to having a very broad base of subject matter, Smashing has a global audience; we’d like to reflect that and bring you interviews from people all over the world. I asked Drew for his thoughts on these first few episodes:

“I was really pleased to be able to launch the Smashing Podcast this year. We spent quite a bit of time in development with it, trying to work out what the best format and tone to take would be. We tried to make it sound like Smashing and embody the same values; a good place to learn and stay informed, but with a sense of fun.

Our early guests have included experts such as Jina Ann, Liz Elcoate, and Jason Pamental. And we’ve spoken to authors of Smashing books Andy Clarke and Heydon Pickering.

The reception so far has been great, and you can always let us know what you think via the contact page. I’m looking forward to releasing episodes with the guests we have lined up for 2020!”

If you haven’t listened to an episode yet, you can catch up by subscribing here, or check out the individual episodes and full transcripts.

Smashing Membership

Topple the Cat showing off its ice skating skillsWe love our Smashing Members! This year you have continued to sign up and support the publication of independent content. We’ve been running webinars (with the help of Scott Whitehead and Bethany Andrew where members get to chat with one another in our Membership Slack, while enjoying free copies of our eBooks, plus a copy of the print magazine! We’re really keen to build on and evolve membership over the next years, and we sincerely thank our members for their support.

We have been running a membership table at our event, where members and prospective members can chat with the team. Our partnership manager, Mariona Jones remembers,

“While running the membership table at SmashingConf, I met a group of attendees who shared their passion for many things, among them open-source, stickers, code, and caffeine while browsing together through the first-ever Smashing print magazine on ethics and privacy and conversing about the relevance of this important topic.”

That’s enough from me! Still, we can’t wrap up 2019 without some thoughts from Vitaly, without who Smashing would not exist at all.

Vitaly on stage in front of a slide saying Welcome

Vitaly opens a SmashingConf (Photo credit Marc Thiele)

“It’s common to think that it’s all about the achievements or goals that make a year special, but for me, this year was full of meeting wonderful people. So, so many people. I’ve had a chance to speak with hundreds of people all around the globe, learning from their experiences and sharing mine. I was lucky to travel to over 40 places this year, from Albania, Serbia and Bosnia-Herzegovina to Kyiv, Sweden and Budapest. I vividly remember some of the stories and experiences I shared over a fire in the evening, in cars on the way somewhere, and in buses talking to strangers I’ll never see again. These were extremely rewarding, valuable and precious moments for me. They are the ones that I’ll be looking back to years from now. In essence, it’s all about people in the end.

“It was wonderful to connect with some of our readers at New Adventures in Nottingham, InfoShare in Gdansk, Poland, BTConf in Dusseldorf, FrontEndUnited in Utrecht, Netherlands, YGLF in Vilnius, Lithuania, perf.now in Amsterdam, Netherlands, and so many others! That said, travel is not without drama. When I was on a short vacation in Albania, I ended up getting lost in the woods in the middle of nowhere at midnight. That was quite scary, but thanks to 6% on my phone and a hardly visible, remote McDonalds sign, I was able to get out in a few hours, returning to the hotel around 5 AM.

“I think that this year at Smashing we’ve learned what it really means to be a team. We had tough and difficult situations, but we pulled together in a respectful, kind and very supportive way, and we kept strong and we made it. It was a year full of challenges and adventures, but in the end, we’ve grown even closer together, and I’m very proud of our team for getting there. I’m also very proud of the fact that we have been exploring topics that are often not seen as particularly interesting nor trendy — accessibility, ethical design, privacy. At our conferences, for example, we’ve looked into common problems and issues that developers and designers struggle with, and tried to find solutions and common techniques to tackle them. It’s something that I strongly believe is important for the health of our industry, and I’m happy to see more discussions around these topics this year.

“My sincere hope is that we’ll establish an even stronger team filling in the gaps we currently have, and we’ll manage to create a very strong alignment within the company. I hope we’ll be able to reach out to more people — especially the new generation of designers and developers — and connect with them. I can’t wait for the books that we’ll be releasing next year as well! I have a number of ideas in mind of things I think we could do, but before jumping there, I want to make sure we are stable, healthy and strong. No rush — I’ve been patient my entire life.”

Onwards To 2020!

The whole team is looking forward to seeing what 2020 brings, and to sharing that with the Smashing Community — wherever you are in the world. Thank you for being part of our journey!

A lineup on stage in front of a screen saying Thank you

The Smashing team on stage in New York (Photo credit: Drew McLellan)
Smashing Editorial
(il)

Source: Smashing Magazine, 2019: A Smashing Year In Review

New Adventures Ahead! (January 2020 Wallpapers)

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New Adventures Ahead! (January 2020 Wallpapers)

New Adventures Ahead! (January 2020 Wallpapers)

Cosima Mielke



Let’s welcome 2020 with a new wallpaper! After all, the new year is the perfect occasion to tidy up your desktop and start on a fresh, blank slate — no clutter, just the things you really need and space for what’s about to come. And some inspiration, of course.

As every month since more than nine years already, artists and designers from across the globe once again took out their favorite tools to create wallpapers to inspire you, make you smile, think, or just to cater for a blob of color on a dark winter day. The wallpapers are available in versions with and without a calendar for January 2020 and can be downloaded for free. And since this little challenge has brought forth so many unique artworks over the past few years, we also assembled a selection of older January favorites at the end of this post. We wish you a wonderful start into the new year and a lot of exciting adventures to cross your way in 2020!

Please note that:

  • All images can be clicked on and lead to the preview of the wallpaper,
  • We respect and carefully consider the ideas and motivation behind each and every artist’s work. This is why we give all artists the full freedom to explore their creativity and express emotions and experience through their works. This is also why the themes of the wallpapers weren’t anyhow influenced by us but rather designed from scratch by the artists themselves.

Submit your wallpaper

Do you have an idea for a February wallpaper design? We are always looking for creative talent to be featured in our wallpapers posts. Don’t be shy, join in! →

New Year, New Beginnings

— Designed by MasterBundles from USA

New Year, New Beginnings

National Popcorn Day

“In this epic Netflix and Chill era, nothing has gotten more important than popcorn during the newest blockbuster! Time to gain awareness about celebrating our delicious guilty pleasure during the movies!

A little story around the wallpaper: Mr Popcorn and Mrs Popcorn are enjoying a great movie with… You guessed it right, popcorn!! But Mr Popcorn is somewhat annoyed as his Mrs eats Popcorn from his head instead of eating from the bucket right in between the loved ones.”

Designed by Nicolas van der Straten Ponthoz from Belgium

National Popcorn Day

It’s Snowing!

“It is January, it’s cold and snowy… In the house, the fireplace is on and it’s hot. Only penguins are enjoying time out there.”

Designed by Veronica Valenzuela from Spain

It’s Snowing!

Month of the Garnet Birthstone

“I wanted to approach the monthly challenge from a more unique perspective. Instead of chosing a cliché subject that has been done way too many times before, I chose a less known, special subject. The birthstone. Enjoy.”

Designed by Bram Copermans from Belgium

Month of the Garnet Birthstone

Rubber Ducky Day

“Winter can be such a gloomy time of the year. The sun sets earlier, the wind feels colder and our heating bills skyrocket. I hope to brighten up your month with my wallpaper for Rubber Ducky Day!”

Designed by Ilya Plyusnin from Belgium

Rubber Ducky Day

Good Intentions

— Designed by Jonathan Verhaegen from Belgium

Good intentions

The King Of Rock And Roll

“On January 8th 1935, the creator of the rock ‘n’ roll genre was born and he’s back for his final debut on this wallpaper!”

Designed by Bailey Lievens from Belgium

The King Of Rock And Roll

Aquaman

“Aquaman relaxing in the ‘nice’ January weather.”

Designed by Ricardo Gimenes from Sweden

Aquaman

Laughter Is An Instant Vacation

“These are polarized times we’re living through. It seems like there is division all around. So sometimes you just have to find the time to remember that the one thing that connects us all is a good laugh. And there is no better laugh than the belly laugh! So on the 24th of January, let’s celebrate one of life’s truly great joys and let it all hang out!”

Designed by Ever Increasing Circles from the United Kingdom

Laughter Is An Instant Vacation

Chocolate Cake Day

“I really love chocolate cake, so when I found out about “Chocolate Cake Day” I had to make a wallpaper about it!”

Designed by Aaron Claes from Belgium

Chocolate Cake Day

Earth’s Rotation Day

— Designed by Bob Storms from Belgium

Earth’s Rotation Day

Go Green & Save The Earth

“Taking care of the Earth is not just a responsibility, it’s a necessity. So I designed a wallpaper to remind everyone what we can do to help save the planet.”

Designed by Farhat Asif from India

Go Green & Save The Earth

Stickers from the 70’s

“I didn’t want to make a typical New Year themed wallpaper for January so I started looking for fun ideas. Apparently January 13th is day of the stickers and so I made something original with this. I wanted to add an extra challenge that was totally out of my comfort zone. So I designed everything in seventies style. Grooovy baby!”

Designed by Bastien Corens from Belgium

Stickers from the 70's

The Wolf’s Month

“I love wolves!”

Designed by Morgane Van Achter from Belgium

Wolfs month

Oldies But Goodies

The beginning of something new, the colors of winter, local New Year’s traditions — these are just a few of the things that inspired people to create a January wallpaper over the years. Below you’ll find a selection of designs from our archives that are just too good to be forgotten. Enjoy! (Please note that these wallpapers don’t come with a calendar.)

Start Somewhere

“If we wait until we’re ready, we’ll be waiting for the rest of our lives. Start today — somewhere, anywhere.”

Designed by Shawna Armstrong from the United States

Start Somewhere

Facts

“I was reminded of a simple fact while I was browsing for inspiration for this wallpaper. I’ve read on Wikipedia that January is the coldest month on most of the northern hemisphere and the hottest one on most of the southern hemisphere. I found it fascinating that someone in Australia is enjoying a surf while I am watching the first snowflakes of the winter. I was hoping to create a wallpaper that will serve as a reminder of the fact that we live in a fascinating world full of varieties and contrasts. The old-worn-out-encyclopedia style hopefully emphasizes the educational theme of the wallpaper.”

Designed by Danijel Gajan from Serbia

Smashing Desktop Wallpapers - January 2012

Hidden Gem

“Kingfishers are called ‘ijsvogels’ (ice-birds) in Dutch. Not because they like the winter cold, but because of the intense blue and teal colors…”

Designed by Franke Margrete from the Netherlands

Hidden Gem

Freedom

“It is great to take shots of birds and think about the freedom they have. Then I start dreaming of becoming one and flying around the world with their beautiful wings.”

Designed by Marija Zaric from Belgrade, Serbia

Freedom

January Is The Month For Dreaming

“It can be very hot in Australia and very cold in Europe so I think that it is a good month for dreaming and making plans.”

Designed by Tazi from Australia

January Is The Month For Dreaming

Travel And Explore

“For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. (Leonardo da Vinci)”

Designed by Dipanjan Karmakar from India

Travel & Explore

A New Beginning

“I wanted to do a lettering-based wallpaper because I love lettering. I chose January because for a lot of people the new year is perceived as a new beginning and I wish to make them feel as positive about it as possible! The idea is to make them feel like the new year is (just) the start of something really great.”

Designed by Carolina Sequeira from Portugal

A New Beginning

Open The Doors Of The New Year

“January is the first month of the year and usually the coldest winter month in the Northern hemisphere. The name of the month of January comes from ‘ianua’, the Latin word for door, so this month denotes the door to the new year and a new beginning. Let’s open the doors of the new year together and hope it will be the best so far!”

Designed by PopArt Studio from Serbia

Open the Doors of the New Year

“I wanted to try my hand at creating a low poly illustration and thought a champagne glass would be fun.”

Designed by Denise Johnson from Chicago

Pop, Fizz, Clink

Oaken January

“In our country, Christmas is celebrated in January when oak branches and leaves are burnt to symbolize the beginning of the New Year and new life. It’s the time when we gather with our families and celebrate the arrival of the new year in a warm and cuddly atmosphere.”

Designed by PopArt Studio from Serbia

Oaken January

Snowy Octopus

— Designed by Karolina Palka from Poland

Snowy Octopus

Soft Wishes

“Let yourself be carried away by the delicate desires of your heart…”

Designed by Katia Piccinni from Italy

Smashing Desktop Wallpapers - January 2012

Boom!

— Designed by Elise Vanoorbeek from Belgium

Boom.

The Early January Bird

“January is the month of a new beginning, hope and inspiration. That’s why it reminds me of an early bird.”

Designed by Zlatina Petrova from Bulgaria

The Early January Bird

Winter Leaves

— Designed by Nathalie Ouederni from France

Winter Leaves

Caucasian Mountains

“From Caucasus with love!”

Designed by Ilona from Russia

Smashing Desktop Wallpapers - January 2012

Wolf-Month

“Wolf-month (in Dutch “wolfsmaand”) is another name for January.”

Designed by Chiara Faes from Belgium

Wolf-Month

Be Awesome Today

“A little daily motivation to keep your cool during the month of January.”

Designed by Amalia Van Bloom from the United States

be awesome today

Blue Neon Sign

— Designed by Jong S. Kim from the United States

Smashing Desktop Wallpaper — January 2013

Join In Next Month!

Thank you to all designers for their participation. Join in next month!

Smashing Editorial
(cm, il)

Source: Smashing Magazine, New Adventures Ahead! (January 2020 Wallpapers)

Smashing Podcast Episode 6 With Luca Mezzalira: What Are Micro-Frontends?

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Smashing Podcast Episode 6 With Luca Mezzalira: What Are Micro-Frontends?

Smashing Podcast Episode 6 With Luca Mezzalira: What Are Micro-Frontends?

Drew McLellan



Luca MezzaliraWe finish off this year with yet another Smashing podcast! This time, we’ll be talking about micro-frontends. What is a micro-frontend? How is it different from the sort of approach we might be taking at the moment? Let’s find out from micro-frontend pioneer, Luca Mezzalira.

Show Notes

Weekly Update

Micro-Frontends

Transcript

Drew McLellan: He’s a Google developer expert on web technologies and manager of the London JavaScript community. With more than 15 years experience, he currently works as VP of Architecture, designing sports video platform DAZN, which delivers on demand sports content to millions of users all watching live. He’s the author of the book Front-End Reactive Architectures for Apress and is also a technical reviewer for Apress, Packt Publishing, Pragmatic Bookshelf, and O’Reilly, as well as being an experienced public speaker at technical conferences all around the world. He’s Italian, sports a handsome beard, and clearly has deep knowledge of the web platform. But did you know he once crossed South America on an ostrich? My smashing friends, please welcome Luca Mezzalira. Hi, Luca. How are you?

Luca Mezzalira: I’m smashing.

Drew: I want to talk to you today about the subject of micro-frontends. Now this is a concept that’s completely new to me, certainly by the name, and I expect it’s new to a lot of our listeners, too. Before we get into micro-frontends themselves, I guess we should understand the problem that you’re looking to address with them. So perhaps you could tell us a little bit about how you see applications in a more traditional way and what sort of problems do those things hit that maybe micro-frontends might be the solution to?

Luca: Okay, that’s a good starting point, in my opinion. So usually when you implement or design a new green field project and you want to work with front end applications, you have a few architecture that you can leverage. You can use a single page application, you can use a server side rendering application, or you can use a multi-page application composed by just simple HTML pages. Obviously those are super valid options and I think very used by many, many developers. The real problem that we’re trying to solve here is how you can scale these concepts with distributed teams to hundreds of developers working on the same codebase, because the reality is when you’re working in these platforms in particular, when you think about SaaS platform for instance, you need to have multiple developers and multiple teams that are working on the same project. And obviously the way how, for instance, you do acquisition or retention is completely different on the way how you expose the catalog or how you show a specific part of a platform.

Luca: So now in my experience I work a lot with single-page application. I work with server-side rendering application, but at some point in DAZN I’d be asked to think about a way to scale our technical team. And I need to come up … if for backend we have some solution that are microservices in this case, so we can scale our APIs independently, and take in consideration that the scale and the volume for a specific throughput on a specific API. On the front end, really, it’s really more difficult because if you think about that, you don’t have technical problem to solve when you need to scale, if you’re using a single page application, for instance. Probably for a server-side rendering you have some, but on a single-page application, for instance, it’s distributed by nature because it’s on client-side, different client-side.

Luca: So the only thing that they are loading are just some static files like CSS and HTML and JavaScript that are served by CDN, and in that case you can scale accordingly, it’s not a big challenge. But the real challenge is how you scale the teams working on the same platform, because sometimes the challenges that are faced by one team could be completely different from the challenges that are faced by another team, and usually what you do is you try to find a lot of tradeoffs between the things. Because if you think, let’s try to think on a normal use case. So usually when you start a platform you’re starting small. So you try to create that quick single-page application, as well you have your monolith, so you just set up everything in your CICD just once for front end and back end, and then you start to iterate on your logic. But the reality is when you have success, you need to evolve this part, and it’s not always maintaining the same architecture that could, let’s say, create the benefit for your business, because maybe you can find some bottlenecks.

Luca: So now going back to the single-page application part. So if we want to scale a single-page application part, the challenge is not technical, it’s with humans if you want. So how we can scale teams working on the same application. So what I did a few years ago is, was the starting to look at a possible architecture that and principles that would allow me to scale the front end as well as the backend. So working on the backend principles so that you can find the microservices. I started to look at the different solution and they came out with the micro-frontends that at the beginning we didn’t even call it that way because obviously for years ago there wasn’t the, let’s say, that name for that specific architecture.

Luca: But the reality is taking a monolith, so a single page application and slicing it in a way that will allow us to focus ourselves in a tiny problem. So a smaller problem than the entire application and trying to solve that in the best way possible. Technically speaking. Obviously that lead to have independent pieces of your frontend application that could be deployed in production without affecting all the others. So the challenge basically for Micro-frontend is trying to figure out their way to take a single page application or server side rendered application and create a artifact of these, let’s say, as close as possible to a business domain, and can be deployed independently.

Drew: So I mean you mentioned micro services on the back end. So conceptually this is a similar sort of solution to the problem. The micro services serve on the back end, but ported over to the front end. Is that a rough equivalence or is it more involved in that?

Luca: Yes. No, it’s a way to solve the same problem it is trying to solve microservices on the back end but on the front end in this time. Usually when I started this journey at the beginning, you know, you start to think about that and you start to evaluate different approaches. And in the last few months I came up with what they call, the Micro-frontend decision framework that basically is four steps that they use in order to, let’s say you identify an approach for Micro-frontend, because if up to now, we usually pick one framework that designed architecture for us and we implement on top of their architecture. If you think about angular or think about React or Redux. You have all the pieces that are needed but you don’t take architectural decisions. You would take a design decisions or how you implement on top of that specific architecture.

Luca: So on Micro-frontend you need to start the step back. So we need to think about how we want to first slice our application. So there are two usually options for that. You can slice horizontally, so you can have multiple micro-frontends in the same view or you can slice vertically. Therefore you always load one Micro-frontend per time. And those decision are quite key because it will then cascade certain other options that you have based on the initial decision to make. So the first, as I said, you decide how you want to slice your application. The second one is how you want to compose your application. So you want to have like, for instance, an app shell that is loading one or multiple micro-frontends in the same view. You want to have, I don’t know, application server that is composing different fragments of your applications, so different Micro-frontend and then serve the final view to your user. Or you want to use edge-side included, it’s a standard that is inside of CDNs in order to compose a page and serve these there.

Luca: Those are three of the options that you have. And then apart from composing, then you need to think how you want to route. So how you route from, I don’t know, /login or /signin to the catalog part or a specific detail object. Also here you have like three option. You can do it at the application server, you can do it on CDN level with Lambda Edge or any other web workers in CloudFlare or anything else. Or you can do a client site. So you have a logic inside your app shell that you say, okay, now for this specific URL you need to load another view or another micro-frontend. And the last bit is how you communicate with Micro-frontend.

Luca: So usually if you have like multiple Micro-frontend on the same page, there is higher complexity on managing this communication, because you need to maintain the different Micro-frontend independent. So that means you cannot have any reference on how the page is structured. So usually you can use stuff like custom events or an event meter that is injected inside each single Micro-frontend. And then the Micro-frontend are communicating together. Obviously in the other case when you have like let’s say a vertical split off your Micro-frontend is way easier, because inside the vertical basically the representation of a vertical Micro-frontend is a single page application or a single page. And in that case it’s easier to let’s say create and share having a shared state across the entire Micro-frontend.

Luca: Then if you think about having multiple Micro-frontend all together, then you should avoid to have states that are shared across Micro-frontend, because otherwise you are coupling things. Instead of the whole concept here is decoupling and have independent deployment. And therefore let’s say the challenges of a horizontal split, which is the first decision you should take or vertical split, are completely different, and we need to be very well aware which one fits our use case.

Drew: So rather than a specific technical solution, micro frontends are very much like a design pattern that you would implement in whatever technology is appropriate for the particular problem you’re trying to solve?

Luca: Yeah, more than technology, I would see that we pick the right architecture for the right job. Just to give you an example, I was talking … there is a famous framework, a fairly new for Micro-frontend, it’s called Luigi framework, that was released by SAP open source. What they are doing is creating some iframes where they are wrapping their Micro-frontend inside it. So now if you think about that, let’s say, using iframes nowadays, you’re on a public website that maybe as the SEO or other features that are mandatory, it could be problematic.

Luca: But in the case of SAP, if you think about that, they have like enterprise application where they can control the browser that the user is using, they can control the environment, they don’t need to be available on a multitude or different version of the browser. So for them these thing allows them to have certain areas of the application that are constant and they have certain areas that are changing independently without any problem. But obviously an iframe solution wouldn’t work in other situation. Just to give another example, Spotify, we’re using iframes at the beginning. In fact the desk publication is still composed by multiple iframes and each single iframe is a tiny application that does, I don’t know, just a music player or just their recommendation, whatever it is. They try to have the same approach on web, but they dismissed that this year in order to move back to a single page application.

Luca: And that means, they explain why in the technical blog, they were saying that obviously if you apply that to millions of users that are using iframes that needs to load every time the same vendors file. And then you have like a lot of dependancies duplicated and the time for interacting with your page would be longer. So in reality, this approach could fit for certain use cases, but they shouldn’t fit for all of them. That’s why I’m saying, as I described before, if you have a decision framework that helps you to address those thing and you can start to say, okay, I sliced the application in this way, therefore I have those options that are available when I want to compose, when I want to route, when I want to communicate, it should guide you in order to have the right decision at the right time.

Luca: Then obviously apart from those four decisions, there are many others. Like how you create consistency in the design system that you have across all the Micro-frontend. Or I don’t know how you manage the dependencies and avoid the clashing of the dependency inside the Micro-frontend, but the reality is those four decisions that I mentioned before will allow you to then take all the others in a quick way without having the problem of overthinking, which is the best solution because you already set the cornerstone, the four pillars, that will allow you to take all the other decision … I don’t say in a easy way, but in a quicker way than a review or the spectrum of opportunities.

Drew: You mentioned before, the way that Micro-frontend can help with the sort of structure of teams within your organization and having lots of people working on the same application. What are some of the implications then and does it make any difference if your teams are distributed or co located or are there any challenges that are faced there?

Luca: Yes. So I can tell you what is the story of DAZN. That is the company where I’m working on. Currently in DAZN, we had like a nice challenge. So currently we have over 300 people that are working on the front and the back end of our platform. It’s an OTT platform that is streaming live at sport events globally. And the interesting bit is if all microservices we know how to manage more or less and we have distributed teams. So we have four dev centers. We’d want to put teams in each single dev centers on the front, and we tried this approach and it work pretty well. So with Micro-frontend we were able to provide different business domains in different locations and allow the cross communication between teams inside a specific business domain, very because the worst case scenario there that if you have to speak with another team on your same business domain, you just reach the walking distance from your desk. If instead you need to discuss specific thing on the distributive team, so with maybe somebody in London instead of Amsterdam, or instead of company in Poland, you just organize a call.

Luca: But those kinds of communication are more rare than the ones that are happening across teams inside the same location. And that’s why we started working on that. So the first thing that they did was looking at how our users were interacting with our website, how did the company was structured. And when we identify the four key areas that we are working on, that are currently acquisition and retention, let’s say porting of their core application on multiple TV’s and mobile and having the core domain that for us is the video player and the discovery phase of our content. And finally all the back office elements. I was able to identify those four areas and we those four areas we assigned for each single dev center.

Luca: Obviously there are some point of contacts between those areas, but then there are ways that you can let’s say mitigate and have some initial workshop with the different teams that are in different location and then work towards the same API contract for instance, or the same goal with having some checkpoints during the development. But the nice thing of approaching that allowed approaching with Micro-frontend is the fact that we finally understand deeply how our system was working. We sit down and we analyze how we were structured and we changed not only the way how we were affected things, but also how the company was working. And that was a kind of a different approach from what they have seen so far. But it’s proving that is working pretty well in the case that each single team can interact with the team of the same location in the same domain.

Luca: So they are talking exactly on the same language if you are talking about the domain driven design. And that is that if they need to interact with other teams, they can literally share the workshop or flying to another dev center and it’s less than a problem. But in this way we let’s say, augment the throughput and reduce the communication overhead, and the extent of dependencies that were happening in other situation that they were working on.

Drew: And do all these teams need to be using like a standardized JavaScript framework? Do they all need to be coding in the same things, they all need to be either React or Angular or to enable the interoperability between them or can people be using different things for different Micro-frontend?

Luca: Yeah. So in DAZN we decided to slice vertically our Micro-frontend and that was a decision that allowed us to have the freedom to pick the technology that we need for each single Micro-frontend. Considering that every time we load one Micro-frontend per time and this means that for instance, that how we have a landing page is different from the sign in / sign up journey. So we can update … we’re mainly using React at the moment. But if, for instance, I remember when React 16 was a release that we were able to release in production React 16, also if it wasn’t in the stable version for just a landing page and see if it was working without affecting all the other teams.

Luca: And then at their own speed, at thier own pace, they were updating their own stuff. So that allows us also to let’s say try new technologies or new assumptions that we have on the existing application with a certain amount of users. Because we implement the also candidate releases for front end. We implement the, let’s say several practices that allows us to just try certain times in production and see how the things are working.

Luca: The beauty of these approaches that we can independently decide to have the right tool for the right job more than having a common denominator across the entire stack. Because as you can imagine, when you started to work on a project, the decision that you made the first few years are probably different on the decision that you made in a trajectory where the company’s growing, the business is evolving and these became more mature and the challenge is completely different. So it wouldn’t be flexible enough or agile enough, if you think about that, the fact that we stick with the same decision we take two years ago. In particular an institution like DAZN, that we move from basically zero to 3000 employees in three years. So as you can imagine it was a massive growth and it was a massive growth for the company as well as on the user base.

Drew: Is there an established way for the different Micro-frontend to share data and to communicate with each other, for example, just to keep each other in step with the same view or is there a way to do that?

Luca: Yes, there is. It depends which of the decision framework, which path you’re going to take. Because if you’re going to take the vertical slice that became very easy. So what we have in order to communicate through Micro-frontend is an app shell that is loading in Micro-frontend inside itself. And what it does is storing everything that has to be, let’s say, shared across different Micro-frontend or on a web storage, either a session or local storage or in memory. And then based on those information, the Micro-frontend is loaded, can retrieve from the app shell to this information and then consume that, amend that or change them. It’s completely up to how you slice the application, but in this case, just to provide an example, if you think when you are authenticated users and you need to go to the sign in page, when you in and the APIs are our consumed and they are providing a JWT token, Micro-frontend is passing these to the app shell and the app shell these starting we saved their web storage.

Luca: Then after that the app shell is loading the new authenticated area for that specific application and those authenticated areas, they’re retrieving the JWT token from the app shell and is performing either a refresh access token or is validating some data starting inside the JWT token. So it’s using basically the information that were produced by another Micro-frontend at their own wheel.

Drew: It sounds like a very interesting concept and I can potentially see lots of big advantages to working this way, but it can’t be without its challenges, surely. Are there any particular things that are more difficult to deal with when architecting things in this way?

Luca: I think first and foremost the main challenges that I see is the shift of mindset. Because before we were used to have a, let’s say, the tech leads or the lead developers that were deciding everything around an entire application taking all decisions. Now finally we move from this centralized entity to a de-centralized entity that is local for each state. As you can imagine, this is bringing some challenges because if before we have someone that is tracing the path, now is that we have, let’s say, multiple people at the top defining the right path inside their domain, and this is a huge shift of mindset.

Luca: On the other side, I think the complexity is accepting sometimes that you doing the wrong abstraction could be, let’s say, more expensive than duplicating code. And that’s I know there’s something that I found very challenging in managing developers because they’re thinking, “Okay, now I can reuse this object or this specific library hundreds of times inside the project,” but the reality is very different. I saw components library that were abstract and they spend a lot of time making that as the best code ever or the best in a perfect shape. But the reality were used just twice. So the effort of doing that, it wasn’t exactly that. I saw on the other side libraries that they started with a couple of use cases for a specific component. And then those use cases became 10 and then the code became unmaintainable.

Luca: So trying to add a new function inside the same component could be more at risk than a benefit. So I think the other thing that we need to understand with Micro-frontend is how much we want to share it and how much we want to duplicate. And there is no harm, honestly, duplicating. In our case for instance we have a duplication of footer and header, and we did that mainly because we changed like three times the header in four years. So as you can imagine the fact that we are centralizing these, are assigned to a team and create an external dependency for all the teams, all the hundreds of developers that we have, is more let’s say an issue that a benefit for the company because we are not adding an enormous value.

Luca: At the same time currently we are refactoring, our shared libraries that would be payment library, because obviously payment has some logic behind that and if we want to change once, we don’t want to apply that twice in multiple parts of the code. We want to have just one library that is a source of truth, but for the header and footer, also if there is a discrepancy or for pixel or there is a function that this is deployed like a week later, it won’t hurt the application.

Drew: So are there some telltale signs that people should look for when evaluating an application and thinking, “Oh yes, this would be a good candidate to move to a Micro-frontend sort of architecture?”

Luca: Yeah, so my suggestion would be first and foremost I wouldn’t start a greenfield project with Micro-frontend unless we know exactly how it should be built. And usually it’s very unlikely that you have this information because, particularly if you have a new platform or a new project and it’s the first time that you are working on this, it could be a nontrivial finding this information. Usually what I suggest is starting with an existing architecture that would be so a single page application and then evolving that. In particular for instance I found, I think that using Micro-frontend for legacy applications or when we want to replace specific part of the application or when we have a project that we want to evolve and scale for multiple teams, those are three use cases that I feel very strong could suit the Micro-frontend architecture. Obviously that doesn’t mean that from now on everything should be made Micro-frontend, because Micro-frontend is not the silver bullet at all.

Luca: What they are is an additional architecture that we can leverage on the front end world. And up to now we had like a certain amount of architectures, now we have an additional one. But that’s a lot of challenges because obviously you need to, if before server side rendering or a single page application, there are clear patterns that were explored and then implemented by several framework and so on. With Micro-frontend currently, is one way to do things. But adding the decision framework probably should allow people to make the right decisions for their use cases. Because often there are a lot of misconceptions on what Micro-frontend are and how they should be used. And lots of people are thinking that maybe let’s say, are evil for, I don’t know, having too many libraries in one view or other things.

Luca: The reality is you need to understand deeply the concept, understand how to implement that and then you can start to work on that. I fully agree that there are technical challenges and there are a lot of decisions that you have to make and you cannot just start straight away with an editor in front of you writing code and thinking, okay, now I’m creating a micro-frontend architecture. Because you need to understand the concept, understand the context and create, also governance around that because the complexity is not just writing the code, it’s also understanding how all the pieces are fitting together in the CICD part the SEO part and so on.

Luca: So Micro-frontend does provide, let’s say a level of flexibility and require a lot of effort for defining the governance right. Because when you have the governance right, everything would be smooth. Often and unfortunately I would say too often, I saw companies that where they don’t spend enough time on the governance side, understanding the CICD for instance, because they don’t think that this is important. But instead for Micro-frontend, like for microservices, having automation right will allow you to speed up the development. If you don’t spend enough time on the automation bit, you risk to have more burden than benefits.

Drew: I guess it’s like so many things in the web development world where people are in danger of diving in with a technical solution before they’ve really understood the problem. And it sounds like with Micro-frontend is very much a case you need to see the problem and then implement the solution to know what problem that you’re solving. I guess the very nature of Micro-frontend make it very easy to start integrating into an existing application, to spot a small problem and swap it out with a Micro-frontend in order to solve that problem. Is that a reasonable suggestion?

Luca: Yeah, I would say so. In this case, the only thing that I would suggest if we start in this way is looking more at the vertical slicing over the horizontal slicing, because otherwise you need to solve so many problems about, let’s assume that for instance you’re using Angular and you want to move to a new version of Angular. If you need to have two Angular version living together without using I-frame, it could be complicated or even not possible. So if you start, you the aspect not from … if you check the challenge, not from the technical point of view, but from the business point of view. Maybe for instance, you can take, I don’t know, the sign-in part on that you want to write with a different version or the same version but more update version of a framework and that could be a good way. And then you route through the path. That could be a good way to replace slowly but steady a specific application.

Luca: What we have done in our case is basically applying the strangler pattern that is a well known pattern for microservices, but on the front end. So based on the URL and based on the browser and country of the user. So slowly but steady, basically we were killing the monolith, that in this case was single page application, releasing our new application more often and see the behaviors of the users, if it was improving the experience, it was causing any problem on our system or not. And that allowed us to provide immediate value to the business, but at the same time allowed us to test our assumptions and see if we were going to the right direction or not.

Drew: It sounds like a very attractive solution to some problems I’m sure a lot of people are facing. If I, as a developer, wanted to start investigating more about Micro-frontend, where would be a good place to start?

Luca: Yes, so currently I’m spending a lot of my spare time trying to advocating around these architecture, because I think there are a lot of misconceptions. On my Medium account. I’ve wrote several articles that are available there as well. A recorded a lot of videos in conferences that you can find on YouTube without any problem. And the other thing I would suggest if you’re looking for some code example on some frameworks, the one that I would recommend to start with is a single SPA, mainly because it has a vertical slicing approach, it’s easier to pick it up and you can start to understand the benefit of this architecture. Then there are many others that are available. Before I mentioned Luigi framework, as well as many others that are currently out there that are allowing you to compose multiple Micro-frontends in the same view.

Luca: Like another one in my head is TailorJS is another interesting. But definitely there is open components that is one developed by Open Table. But in general there are plenty of opportunity if you start to search about Micro-frontend, they’re out there.

Drew: That sounds great. Is there anything else that you wanted to talk about with regard to the Micro-frontends?

Luca: Yeah. Personally I would suggest to take an open mind approach on learning this architecture and this approach, technical approach, mainly because I believe that there is a lot of good, but we need to, let’s say, invest a bit of time and spend a bit of time to deeply understand how the things are working. Because obviously there isn’t, just one way to do things. We are used that we take a framework and immediately we start to work on it and it’s super productive, if you think about that.

Luca: But in this case you need to spend a bit of more time understanding, as you said a couple of times, the problem. Understand which is the pattern that would allow you to express better not only from a technical point of view but those two from our organizational point of view, the solution that you have in mind.

Drew: So I’ve been learning all about Micro-frontend today. What have you been learning about lately?

Luca: Recently there are two things that I’m learning. So last week I was in Las Vegas during the AWS event and is obviously a cloud conference. Pretty amazing, 70,000 people, a lot of sessions that were spreading several hotels in Vegas. And there for me, a serverless is a paradigm that I’m studying the most because I truly believe that in the future that will be the way how we are going to design and implement software and obviously AWS is very prominent on this approach.

Luca: And the second topic is around management and how to be a leader of a tech team. Because obviously I’m SVP of architecture. I have a team of architects that I’m leading and you can never rest because you need to not only to be on top of the technical side, but you need also to understand the people problems, understand how you can make them successful. Because obviously if they are successful, you are successful. You are first a technical facilitator to a certain extent. So that for me, those for me are the two things that currently I’m studying on top of exploring the Micro-frontend world.

Drew: If you, dear listener, would like to hear more from Luca, you can follow him on Twitter where he’s @LucaMezzalira or find his activities collected together at Lucamezzalira.com. Thanks for joining us today, Luca. Did you have any parting words?

Luca: No, but thank you very much for listening up to now.

Smashing Editorial
(dm, ra, il)

Source: Smashing Magazine, Smashing Podcast Episode 6 With Luca Mezzalira: What Are Micro-Frontends?

5 Things To Stop Doing In Mobile App Design

dreamt up by webguru in Uncategorized | Comments Off on 5 Things To Stop Doing In Mobile App Design

5 Things To Stop Doing In Mobile App Design

5 Things To Stop Doing In Mobile App Design

Suzanne Scacca



I move to a new state every two to three years, so it’s important for me to live “light”. Every time I prepare to move, I go through the “Do I really need to keep this?” exercise. Although I’ve been doing this for almost 20 years, it never gets any easier. I wonder things like:

What if I sell my bed and never have a comfortable night’s sleep again?

What if I get rid of the fancy dress I wore once but might need for some hypothetical future event?

What if I decide to start baking cupcakes again and don’t have my cupcake tin anymore?

It’s easy to get attached to things when they served you well at one time or another. But if you take a closer look at the “stuff” you’ve accumulated, you’ll realize that a lot of it has lost its usefulness along the way.

I think it’s important to run through a similar type of decluttering exercise in the work you do as a designer. That way, the apps you build always look fresh and modern instead of weighed down by antiquated features or functionality that at one time had a purpose.

Before you start charging ahead into the new year, take a moment to reflect on how you approach mobile app design. If you’re still holding onto components or functionality that no longer serve any purpose or, worse, intrude on the user experience, it’s time for a change.

Want some help? I’m going to run through some elements you can afford to scrap from mobile app builds in 2020 and beyond.

Related Reading on SmashingMag:

1. Harmful FOMO Elements

You know why marketers, influencers, and designers use FOMO (i.e. it can be really effective in boosting sales). However, you also know how damaging it can be for users’ mindsets (not to mention the distrust they feel towards brands as a result).

You could avoid FOMO altogether, but it’s a tricky thing, isn’t it?

You know that (when left to their own devices) mobile app users may forget that your app even exists on their phones without something to pull them back in. But it’s too easy to go overboard with FOMO-inducing components.

For example, this is ToonBlast:

ToonBlast home screen countdown timers

The ToonBlast gaming app has numerous modules and countdown timers to induce constant FOMO. (Image source: ToonBlast) (Large preview)

The home screen is incredibly overwhelming. More than that, those ticking clocks (there are four of them) are a nightmare for users who can’t help but click on things they feel they’re going to miss out on by not doing so. And for users who can ignore the timers, they won’t be completely unaffected by them either. The game displays pop-up reminders for each of the countdowns. It’s impossible to ignore them.

This is FOMO at its absolute worst.

Even if reminders for each of the countdowns were sent as push notifications instead of disruptive pop-ups, it still would be bad for the user experience. There are just too many things competing for the user’s attention and each of the clocks is like a ticking time bomb.

I know it might seem like giving app users more reasons to engage is a good idea, especially if you’re struggling to attract and retain users. But if that’s really an issue, then you need to work on improving the core product first and foremost.

Going forward, I think we’d all do well to move away from harmful FOMO elements and embrace more simplified and stronger core products.

If you’re not sure what that looks like, I’d recommend turning your attention to Instagram:

Instagram FOMO-free

Instagram is working on removing FOMO from its app. (Image source: Instagram) (Large preview)

Instagram is a simple and straightforward product. Users turn their news feeds into personal curations of people and accounts they want to follow while sharing their own content with the world.

Now, Instagram isn’t completely FOMO-free as you can see from the Stories bar at the top of the page. However, there’s nothing really urgent about the way these stories are displayed. They don’t take up much space in the app (unlike the way Facebook handles it, for instance) nor are there any screaming alarms that say, “Hey! So-and-so’s story is about to expire! Watch it now!”

That said, Instagram is working to remove the harmful effects of FOMO in its app by doing away with like counters and cracking down on influencers and companies that don’t mark ads as such. If you want to create a strong yet simple product that keeps harmful FOMO elements out of the picture, keep this one on your radar.

2. Out-of-Context Access Requests

Unlike mobile websites and PWAs, mobile apps have the ability to get in front of 100% of users who activate push notifications. But that’s the catch. Your users have to be willing to press “OK” or “Allow” when you display that push notification (or phone access) request pop-up.

So, how do you get more of them to do that without constantly shoving those requests down their throats?

Some brands haven’t figured this out yet, to be honest. Take Snapchat, for example.

Snapchat push notification request

Snapchat doesn’t like when users disable notifications and phone access. (Image source: Snapchat) (Large preview)

This is one of those apps that just goes way overboard when it comes to requesting access to users’ devices. It wants to:

  • Send push notifications.
  • Use the camera.
  • Use the microphone.
  • Access saved photos.
  • Enable location tracking.
  • And so on.

Rather than ask for access when it’s relevant, it often sends a deluge of requests first thing when users sign into the app. That’s the wrong way to create a welcoming environment for your users.

A better way to go about asking for access or permissions would be to place it in the context of the app — and only when it makes sense. I’ll show you a couple of examples.

This is the app for ParkWhiz:

ParkWhiz location tracking request

ParkWhiz reminds users about the benefits of enabling location tracking. (Image source: ParkWhiz) (Large preview)

Look at the section called “Help Us Find You” toward the bottom.

Not only does ParkWhiz gently remind users to enable location tracking on their devices, but it does so by explaining the reasons why it would benefit them to do so. Notice also that this isn’t displayed in an intrusive pop-up at the point of entry. Instead, it’s in a spot in the app where, when enabled, it can help streamline the search experience.

YouTube is another app that does this well.

YouTube push notification tooltip

YouTube displays a small tooltip to remind users to turn on notifications. (Image source: YouTube) (Large preview)

In this example, YouTube quickly displays a tooltip over the disabled notification icon. The notice reads:

“You’re missing out on subscriptions! Tap the bell to turn on notifications.”

They’re right. I’m subscribed to this channel and, yet, I haven’t received notifications (push or email) about new videos for a while. I hadn’t realized this until I saw this reminder.

The way this is handled is nice. It makes users stop and think about what they’re missing out on instead of rushing to close out another request pop-up. It also doesn’t force them to turn on push for everything. They can customize which notifications they receive.

Push notifications are supposed to be helpful. And access to your users’ phones is supposed to enhance their experience. That’s why it’s important to ask for their cooperation in enabling these features within the right context. Rather than bombard them with request after request at the outset of installing or opening an app, deliver them within the experience as in-line elements.

3. Unnecessary Icon Labels

Note that this point is called unnecessary icon labels and not just a sweeping generalization of all of them. That’s because there are certain parts of an app where icon labels still work well. Like the navigation bar.

However, I’ve noticed an alarming trend lately whereby apps pair every page or tab name with a matching icon. There are a number of reasons why this is an issue and I’m going to use the GEICO app to demonstrate them.

GEICO mobile app home page

The GEICO mobile app home page comes with a list of services and modules paired with icons. (Image source: GEICO) (Large preview)

This home page makes it easy for users to take advantage of their auto insurance and related services on the go. Let’s focus on the “Vehicle Trouble” section though.

There are four tabs:

  • Emergency Roadside Service represented by a tow truck icon,
  • Start a New Claim represented by a car with what looks like a crash symbol,
  • Report Glass Damage represented by a car with a crack on the windshield,
  • View Recent Claims represented by a clipboard with the letter “C” on it.

The icons aren’t all that easy to decipher (except the tow truck) and I’m just not sure they add any value here. Really, if you can’t think of anything better than putting a letter “C” on a clipboard to represent claims, maybe icons aren’t needed after all?

Next, let’s take a look at the GEICO app’s list of settings:

GEICO app navigation

The GEICO app’s navigation pairs each page with an icon. (Image source: GEICO) (Large preview)

There are a lot of settings pages here. Not only that, they’re not the kinds of pages you’d typically see in other mobile apps, so the designer has had to get creative in pairing them with icons.

If this navigation didn’t have icons, I think it would be much easier to read through the options. The same goes for the home page. Without the icons, the font size could be increased so the focus could strictly be on the page names and insured users could get to the information they need more quickly. As it stands now, the icons are just wasted space.

Let’s look at another example.

Rover is an app that pet owners can use to book pet sitting and walking services. Icons are used sparingly through the app to distinguish services from one another as well as to label the navigation pages.

Rover mobile app with icons

The Rover mobile app includes icons to label its navigation and services. (Image source: Rover) (Large preview)

I don’t think the icons on this page are necessary in terms of expediting user selection (e.g. “I need overnight house sitting so I’m going to choose the moon-over-the-house icon.”). That said, I don’t think the icons detract from the button text since each option is clearly labeled with big, bold font. What’s more, the icons do a nice job of bringing balance to the buttons so there aren’t huge white gaps in the middle.

Now, let’s look at what the designer has chosen to do under the “More” tab:

Rover app settings

Rover’s list of “More” settings don’t include icons like the rest of the app. (Image source: Rover) (Large preview)

This is similar to GEICO’s slide-out navigation menu. But notice how Rover’s is text only. Considering how common these settings are from app to app, it would’ve been easy enough to add icons to each, but the designer chose to leave them off and I think that was a good decision.

There’s a time and place when icons serve a purpose. As far as labeling a secondary navigation menu in your app, it’s time to do away with that. I’d also express caution over labeling pages with icons if it’s a struggle to find a match. That should be a sign to you that they’re not needed to begin with.

4. Excessively Long Home Pages

In web design, we’re seeing much shorter home pages than in years past, thanks to the need for more efficient mobile experiences. So, why isn’t this something we’re doing in mobile app design?

There are some apps where this isn’t an issue. Namely, ones where there’s no scrolling at all (e.g. dating apps, gaming apps, etc.). And there are some cases where endless scrolling on the home page is fine (e.g. news and social media apps).

But what about other apps?

Listings apps (like for real estate or travel) sometimes have a hard time with this. For example, this is the top of the Airbnb mobile app:

Airbnb app home page

Airbnb app home page with search bar and categories. (Image source: Airbnb) (Large preview)

This part of the page is well done and includes everything users need to find what they’re looking for:

  • A search bar,
  • A list of travel categories to swipe through,
  • Quick links to recent search queries.

But for some reason, Airbnb has designed this home page to go on and on and on with sections for:

  • Top-rated experiences,
  • Airbnb Plus places to stay,
  • Introducing Airbnb Adventures,
  • Places to stay around the world,
  • Featured Airbnb Plus destinations,
  • Stay with a superhost,
  • Unique places to stay for your next trip,
  • Explore New York City,
  • And on and on it goes.

Airbnb promotional content

Airbnb includes over a dozen sections of content on the home page of its app. (Image source: Airbnb) (Large preview)

I’m not sure what the logic was here. While I understand wanting to help your users by providing them with useful recommendations, this goes way overboard. It’s not even as though this is personalized content based on the user’s profile or recent searches. It’s just a smattering of categories that, if anything, are going to overload and overwhelm users with options.

If the app you’re building or have built runs into a similar problem, check out Hotels.com for inspiration:

Hotels.com Discovery page in app

The Hotels.com app provides users with a search bar and recently viewed hotels upon entering the app. (Image source: Hotels.com) (Large preview)

Unlike Airbnb, Hotels.com’s home “Discover” page is short. All it takes is three swipes to get to the bottom of the page. Users see sections for:

  • Recent searches,
  • A city guide (based on a recent query),
  • Last-minute deals,
  • Current bookings,
  • Hotels.com Rewards standings (if relevant).

For the most part, the content is 100% relevant to the user and not just meant to promote every possible service or feature of the app.

If you really feel like users would benefit from seeing every possible feature, create a secondary navigation for it. That way, they can quickly scan through the options and pick the one(s) they’re most interested in. When you give them an endless home page to scroll through and too many listings and buttons to click, you’re only going to make it harder for them to take action.

5. Dark Patterns in Ads

You have to monetize a mobile app if you’re going to make the original investment worth your while. It’s as simple as that.

But I’ve recently encountered some very scary dark patterns in mobile app monetization — specifically, with the way ads are designed. And it’s got me wondering if third-party ad networks are really the smartest way to monetize if they’re going to compromise everything you’ve done to create an awesome in-app experience otherwise.

Now, I understand that app designers usually don’t have any role in designing the ads that appear. That said, do you really think your users know anything about ad networks and how those ad placements get inside your app? Of course not!

So, when one of your users has a bad experience with an ad, what do you think is going to happen? They’re not going to think:

“Oh, that advertiser is terrible for doing that.”

Instead, they’re going to think:

“If I see one more ad like this, I’m uninstalling this app.”

Let me show you some examples of ads that will push the limits of your users’ patience.

This is Wordscapes, a gaming app I’m quite fond of:

A cutoff banner ad in Wordscapes app

A banner ad at the bottom of the Wordscapes app is cut off. (Image source: Wordscapes) (Large preview)

I’ve been playing Wordscapes for a long time and when I first started, it was great. The banner ads were there, but they never really got in the way. And the interstitial video ads only appeared every few rounds or so. They were always easy to dismiss, too.

Over the past year or so, however, the quality of ads has majorly deteriorated. Take the banner ad above. That’s actually a video ad that doesn’t fit in the allotted space.

Then, you have this badly designed banner ad for Jynarque:

Dark banner ad for Jynarque

A banner ad that’s too dark appears at the bottom of Wordscape (Image source: Wordscapes) (Large preview)

Neither of these banner ads are really dark patterns. However, they do suggest there’s something not quite right about where Wordscapes is sourcing their ad content from.

Now, I’m going to show you some of the more deceptive ads I’ve come across.

This is an ad from Showtime to promote the TV show Shameless:

Wordscapes interstitial ad for Showtime

Wordscapes shows an interstitial video ad for Showtime’s Shameless. (Image source: Wordscapes) (Large preview)

See the number “5” in the top-right corner? That’s a countdown timer, which should tell users how long they have to wait until they can dismiss the ad. However, when the timer is up, this icon appears:

Showtime ad without an exit

A Showtime ad provides users with an untraditional escape after the timer runs out. (Image source: Wordscapes) (Large preview)

The timer gets to “0” and is replaced by this button. It’s not the traditional “X” that app users are accustomed to when it comes to watching ads, so they might not realize this will take them back into the game. In fact, they might misinterpret this “Next” symbol as a “Play” button and watch the ad in full. While it’s nice that Showtime gives users an exit, it would be better if the iconography were consistent with other video ads.

Then, there’s this interstitial ad for DoorDash:

DoorDash ad with no exit

A DoorDash ad includes two fake “X” buttons. (Image source: Wordscapes) (Large preview)

This is what the ad looks like the second it appears on the screen, which is actually encouraging.

“An ad that’s going to let us exit out of it right away! Woohoo!”

But that’s not the case at all. Notice how there are two X’s in the top-right corner. One of them looks fake (the plain “X” symbol) while the other looks like an “X” you’d use to dismiss an ad.

The first time I saw this, I clicked on the good “X”, hoping my finger would be small enough to miss the fake target. Yet, this is where I ended up:

DoorDash ad to app store exit

An ad for DoorDash tries to take Wordscapes visitors to the app store (Image source: Wordscapes) (Large preview)

The click takes users out of the Wordscapes app and tries to move them to the app store. After hitting “Cancel” and sitting through five more seconds of the DoorDash ad, this new “X” appears in the top-right corner:

DoorDash deceptive mobile ad

DoorDash finally displays the real exit button for its mobile ad. (Image source: Wordscapes) (Large preview)

At this point, I can’t imagine users are very happy with DoorDash or Wordscapes for this experience.

These examples of bad ads and dark patterns in monetization are just the tip of the iceberg, too. There are ads that:

  • Provide no timer or indication of when the ad will end.
  • Switch the placement of the “X” so users unintentionally click the ad instead of leave it.
  • Auto-play sound even when the device’s sound is turned off.

I know I’m picking on Wordscapes because I spend the most time inside the app, but it’s not the only one whose reputation is being hurt by third-party ad content.

Again, I recognize that you have no say in the design or execution of ads that come from ad networks. That said, I’d really urge you to talk to your clients about being more discerning about where they source their ads from. If mobile ads continue to be this bad, it might be worth sourcing your own ad content from partners and sponsors you trust instead of random companies that use deceptive advertising tactics.

Wrapping Up

There are a ton of reasons to declutter your mobile app designs. But if these examples have demonstrated anything, the most important reason to clean up is to get rid of useless and sometimes harmful design elements or techniques.

And if you’re having a hard time getting rid of the excess, I’d encourage you to reevaluate the core product. If it’s not strong enough to stand on its own, in its simplest of forms, then it’s time to go back to the drawing board because no amount of distractions you fill it with will make it a worthwhile download for your users.

Smashing Editorial
(ra, il)

Source: Smashing Magazine, 5 Things To Stop Doing In Mobile App Design

Helping Browsers Optimize With The CSS Contain Property

dreamt up by webguru in Uncategorized | Comments Off on Helping Browsers Optimize With The CSS Contain Property

Helping Browsers Optimize With The CSS Contain Property

Helping Browsers Optimize With The CSS Contain Property

Rachel Andrew



In this article, I’m going to introduce a CSS Specification that has just become a W3C Recommendation. The CSS Containment Specification defines a single property, contain, and it can help you to explain to the browser which parts of your layout are independent and will not need recalculating if some other part of the layout changes.

While this property exists for performance optimization reasons, it can also affect the layout of your page. Therefore, in this article, I’ll explain the different types of containment you can benefit from, but also the things you need to watch out for if applying contain to elements in your site.

The Problem Of Layout Recalculation

If you are building straightforward web pages that do not dynamically add or change elements after they have loaded using JavaScript, you don’t need to worry about the problem that CSS Containment solves. The browser only needs to calculate your layout once, as the page is loaded.

Where Containment becomes useful is when you want to add elements to your page without the user needing to reload it. In my example, I created a big list of events. If you click the button, the first event is modified, a floated element is added, and the text is changed:

A listing of items with a button to change some of the content in the first item

(See the initial example on CodePen)

When the content of our box is changed, the browser has to consider that any of the elements may have changed. Browsers are in general pretty good at dealing with this, as it’s a common thing to happen. That said, as the developer, you will know if each of the components is independent, and that a change to one doesn’t affect the others, so it would be nice if you could let the browser know this via your CSS. This is what containment and the CSS contain property gives you.

How Does Containment Help?

An HTML document is a tree structure which you can see when inspecting any element with DevTools. In my example above, I identify one item that I want to change by using JavaScript, and then make some changes to the internals. (This means that I’m only changing things inside the subtree for that list item.)

DevTools with the list item of the featured item expanded to see the elements inside

Inspecting a list item in DevTools

Applying the contain property to an element tells the browser that changes are scoped to the subtree of that element, so that the browser can do any possible optimizations — safe in the knowledge that nothing else outside of that element will change. Exactly what a particular browser might do is down to the engine. The CSS property simply gives you — as the developer and expert on this layout — the chance to let it know.

In many cases, you will be safe to go right ahead and start using the contain property, however, the different values come with some potential side effects which are worth understanding before adding the property to elements in your site.

Using Containment

The contain property can set three different types of containment:

  • layout
  • paint
  • size

Note: There is a style value in the Level 2 Specification. It was removed from Level 1, so does not appear in the Recommendation, and is not implemented in Firefox.

Layout

Layout containment brings the biggest benefits. To turn on layout containment, use the following snippet:

.item {
  contain: layout;
}

With layout containment enabled, the browser knows that nothing outside the element can affect the internal layout, and nothing from inside the element can change anything about the layout of things outside it. This means that it can make any possible optimizations for this scenario.

A few additional things happen when layout containment is enabled. These are all things which ensure that this box and contents are independent of the rest of the tree.

The box establishes an independent formatting context. This ensures that the content of the box stays in the box — in particular floats will be contained and margins will not collapse through the box. This is the same behavior that we switch on when we use display: flow-root as in explained in my article “Understanding CSS Layout And The Block Formatting Context”. If a float could poke out of your box, causing following text to flow around the float, that would be a situation where the element was changing the layout of things outside it, making it a poor candidate for containment.

The containing box acts as the containing block for any absolutely or fixed position descendants. This means it will act as if you had used position: relative on the box you have applied contain: layout.

The box also creates a stacking context. Therefore z-index will work on this element, it’s children will be stacked based on this new context.

If we look at the example, this time with contain: layout, you can see that when the floated element is introduced it no longer pokes out the bottom of the box. This is our new Block Formatting Context in action, containing the float.

A listing of items, a floated element is contained inside the bounds of the parent box

Using contain: layout the float is contained (See the layout containment example on CodePen)

Paint

To turn on paint containment, use the following:

.item {
  contain: paint;
}

With paint containment enabled, the same side effects as seen with layout containment occur: The containing box becoming an independent formatting context, a containing block for positioned elements, and establishing a stacking context.

What paint containment does is indicate to the browser that elements inside the containing block will not be visible outside of the bounds of that box. The content will essentially be clipped to the box.

We can see this happen with a simple example. Even if we give our card a height, the floated item still pokes out the bottom of the box, due to the fact that the float is taken out of flow.

A floated box poking out the bottom of a containing box

The float is not contained by the list item

With paint containment turned on the floated item is now clipped to the size of the box. Nothing can be painted outside of the bounds of the element with contain: paint applied.

A box with a floated box inside which has been cut off where it escapes the box

The content of the box is clipped to the height of the box (See the paint example on CodePen)

Size

Size containment is the value that is most likely to cause you a problem if you aren’t fully aware of how it works. To apply size containment, use:

.item {
  contain: size;
}

If you use size containment then you are telling the browser that you know the size of the box and it is not going to change. This does mean that if you have a box which is auto-sized in the block dimension, it will be treated as if the content has no size, therefore the box will collapse down as if it had no contents.

In the example below, I have not given the li a height; they also have contain: size applied. You can see that all of the items have collapsed as if they had no content at all, making for a very peculiar looking listing!

A listing of items with a button to change some of the content in the first item

(See the size example on CodePen)

If you give the boxes a height then the height will be respected when contain: size is used. Alone, size containment will not create a new formatting context and therefore does not contain floats and margins as layout and paint containment will do. It’s less likely that you would use it alone; instead, it is most likely you would apply it along with other values of contain to be able to get the most possible containment.

Shorthand Values

In most cases, you can use one of two shorthand values to get the best out of containment. To turn on layout and paint containment, use contain: content;, and to turn on all possible containment (keeping in mind that items which do not have a size will then collapse), use contain: strict.

The Specification says:

contain: content is reasonably “safe” to apply widely; its effects are fairly minor in practice, and most content won’t run afoul of its restrictions. However, because it doesn’t apply size containment, the element can still respond to the size of its contents, which can cause layout-invalidation to percolate further up the tree than desired. Use contain: strict when possible, to gain as much containment as you can.”

Therefore, if you do not know the size of the items in advance, and understand the fact that floats and margins will be contained, use contain: content. If you do know the size of items in addition to being happy about the other side effects of containment, use contain: strict. The rest is down to the browser, you have done your bit by explaining how your layout works.

Can I Use Containment Now?

The CSS Containment specification is now a W3C Recommendation which is what we sometimes refer to as a web standard. In order for the spec to get to this stage, there needed to be two implementations of the feature which we can see in both Firefox and Chrome:

Screenshot of the browser support information on Containment on Can I Use

Browser support for containment (Source: Can I Use)

As this property is transparent to the user, it is completely safe to add to any site even if you have lots of visitors in browsers that do not support it. If the browser doesn’t support containment then the visitor gets the experience they usually get, those in supporting browsers get the enhanced performance.

I would suggest that this is a great thing to add to any components you create in a component or pattern library, if you are working in this way it is likely each component is designed to be an independent thing that does not affect other elements on the page, making contain: content a useful addition.

Therefore, if you have a page which is adding content to the DOM after load, I would recommend giving it a try — if you get any interesting results let me know in the comments!

The following resources will give you some more detail about the implementation of containment and potential performance benefits:

Smashing Editorial
(il)

Source: Smashing Magazine, Helping Browsers Optimize With The CSS Contain Property