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CSS containment in Chrome 52 | Blog | Chrome for Developers
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lang="de" >Deutsch</a> </li> <li role="presentation"> <a role="menuitem" lang="es_419" >Español – América Latina</a> </li> <li role="presentation"> <a role="menuitem" lang="fr" >Français</a> </li> <li role="presentation"> <a role="menuitem" lang="id" >Indonesia</a> </li> <li role="presentation"> <a role="menuitem" lang="it" >Italiano</a> </li> <li role="presentation"> <a role="menuitem" lang="nl" >Nederlands</a> </li> <li role="presentation"> <a role="menuitem" lang="pl" >Polski</a> </li> <li role="presentation"> <a role="menuitem" lang="pt_br" >Português – Brasil</a> </li> <li role="presentation"> <a role="menuitem" lang="vi" >Tiếng Việt</a> </li> <li role="presentation"> <a role="menuitem" lang="tr" >Türkçe</a> </li> <li role="presentation"> <a role="menuitem" lang="ru" >Русский</a> </li> <li role="presentation"> <a role="menuitem" lang="he" >עברית</a> </li> <li role="presentation"> <a role="menuitem" lang="ar" >العربيّة</a> </li> <li role="presentation"> <a role="menuitem" lang="fa" >فارسی</a> </li> <li role="presentation"> <a role="menuitem" lang="hi" >हिंदी</a> </li> <li role="presentation"> <a role="menuitem" lang="bn" >বাংলা</a> </li> <li role="presentation"> <a role="menuitem" lang="th" >ภาษาไทย</a> </li> <li role="presentation"> <a role="menuitem" lang="zh_cn" >中文 – 简体</a> </li> <li role="presentation"> <a role="menuitem" lang="zh_tw" >中文 – 繁體</a> </li> <li role="presentation"> <a role="menuitem" lang="ja" >日本語</a> </li> <li role="presentation"> <a role="menuitem" lang="ko" >한국어</a> </li> </ul> </devsite-language-selector> <devsite-user enable-profiles id="devsite-user"> <span class="button devsite-top-button" aria-hidden="true" visually-hidden>Sign in</span> </devsite-user> </div> </div> </div> <div class="devsite-collapsible-section devsite-header-no-lower-tabs "> <div class="devsite-header-background"> <div class="devsite-product-id-row" > <div class="devsite-product-description-row"> <ul class="devsite-breadcrumb-list" > <li class="devsite-breadcrumb-item "> <a href="https://developer.chrome.com/blog" class="devsite-breadcrumb-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Lower Header" data-value="1" track-type="globalNav" track-name="breadcrumb" track-metadata-position="1" track-metadata-eventdetail="Blog" > Blog </a> </li> </ul> </div> </div> </div> </div> </div> </devsite-header> <devsite-book-nav scrollbars hidden> <div class="devsite-book-nav-filter" hidden> <span class="filter-list-icon material-icons" aria-hidden="true"></span> <input type="text" placeholder="Filter" aria-label="Type to filter" role="searchbox"> <span class="filter-clear-button hidden" data-title="Clear filter" aria-label="Clear filter" role="button" tabindex="0"></span> </div> <nav class="devsite-book-nav devsite-nav nocontent" aria-label="Side menu"> <div class="devsite-mobile-header"> <button type="button" id="devsite-close-nav" class="devsite-header-icon-button button-flat material-icons gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Close navigation" aria-label="Close navigation"> </button> <div class="devsite-product-name-wrapper"> <a href="/" class="devsite-site-logo-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Site logo" track-type="globalNav" track-name="chromeForDevelopers" track-metadata-position="nav" track-metadata-eventDetail="nav"> <picture> <source srcset="https://www.gstatic.com/devrel-devsite/prod/v38a693baeb774512feb42f10aac8f755d8791ed41119b5be7a531f8e16f8279f/chrome/images/lockup-dark-theme.svg" media="(prefers-color-scheme: dark)" class="devsite-dark-theme" alt="Chrome for Developers"> <img src="https://www.gstatic.com/devrel-devsite/prod/v38a693baeb774512feb42f10aac8f755d8791ed41119b5be7a531f8e16f8279f/chrome/images/lockup.svg" class="devsite-site-logo" alt="Chrome for Developers"> </picture> </a> <span class="devsite-product-name"> <ul class="devsite-breadcrumb-list" > <li class="devsite-breadcrumb-item "> </li> </ul> </span> </div> </div> <div class="devsite-book-nav-wrapper"> <div class="devsite-mobile-nav-top"> <ul class="devsite-nav-list"> <li class="devsite-nav-item"> <a href="/case-studies" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Tab: Get inspired" track-name="get inspired" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Get inspired" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Get inspired </span> </a> </li> <li class="devsite-nav-item"> <a href="/blog" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Tab: Blog" track-name="blog" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Blog" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip 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in chrome" data-category="Site-Wide Custom Events" data-label="Responsive Tab: New in Chrome" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > New in Chrome </span> </a> </li> </ul> </div> <div class="devsite-mobile-nav-bottom"> <ul class="devsite-nav-list" menu="Docs" aria-label="Side menu" hidden> <li class="devsite-nav-item devsite-nav-heading"> <span class="devsite-nav-title" tooltip > <span class="devsite-nav-text" tooltip > Build with Chrome </span> </span> </li> <li class="devsite-nav-item"> <a href="/docs/web-platform" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Web Platform" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Web Platform </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/capabilities" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Capabilities" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Capabilities </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/chromedriver" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: ChromeDriver" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > ChromeDriver </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/extensions" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Extensions" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Extensions </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/webstore" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Chrome Web Store" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Chrome Web Store </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/chromium" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Chromium" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Chromium </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/aurora" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Aurora" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Aurora </span> </a> </li> <li 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<span class="devsite-nav-text" tooltip > Release notes </span> </a> </li> <li class="devsite-nav-item devsite-nav-heading"> <span class="devsite-nav-title" tooltip > <span class="devsite-nav-text" tooltip > Productivity </span> </span> </li> <li class="devsite-nav-item"> <a href="/docs/devtools" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: DevTools" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > DevTools </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/lighthouse" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Lighthouse" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Lighthouse </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/crux" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Chrome UX Report" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Chrome UX Report </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/accessibility" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Accessibility" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Accessibility </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/workbox" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Workbox" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Workbox </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/puppeteer" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Puppeteer" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Puppeteer </span> </a> </li> <li class="devsite-nav-item devsite-nav-heading"> <span class="devsite-nav-title" tooltip > <span class="devsite-nav-text" tooltip > Experience </span> </span> </li> <li class="devsite-nav-item"> <a href="/docs/ai" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: AI" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > AI </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/performance" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Performance" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Performance </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/css-ui" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: CSS and UI" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > CSS and UI </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/identity" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Identity" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Identity </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/payments" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Payments" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Payments </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/privacy-security" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Privacy and security" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Privacy and security </span> </a> </li> <li class="devsite-nav-item devsite-nav-heading"> <span class="devsite-nav-title" tooltip > <span class="devsite-nav-text" tooltip > Resources </span> </span> </li> <li class="devsite-nav-item"> <a href="/docs" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: All documentation" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > All documentation </span> </a> </li> <li class="devsite-nav-item"> <a href="https://web.dev/baseline" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Baseline" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Baseline </span> </a> </li> <li class="devsite-nav-item"> <a href="https://web.dev" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: web.dev" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > web.dev </span> </a> </li> <li class="devsite-nav-item"> <a href="https://pagespeed.web.dev" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: PageSpeed Insights audit" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > PageSpeed Insights audit </span> </a> </li> </ul> </div> </div> </nav> </devsite-book-nav> <section id="gc-wrapper"> <main role="main" id="main-content" class="devsite-main-content" has-sidebar > <div class="devsite-sidebar"> <div class="devsite-sidebar-content"> <devsite-toc class="devsite-nav" role="navigation" aria-label="On this page" depth="2" scrollbars ></devsite-toc> <devsite-recommendations-sidebar class="nocontent devsite-nav"> </devsite-recommendations-sidebar> </div> </div> <devsite-content> <article class="devsite-article"> <div class="devsite-article-meta nocontent" role="navigation"> <ul class="devsite-breadcrumb-list" aria-label="Breadcrumb"> <li class="devsite-breadcrumb-item "> <a href="https://developer.chrome.com/" class="devsite-breadcrumb-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Breadcrumbs" data-value="1" track-type="globalNav" track-name="breadcrumb" track-metadata-position="1" track-metadata-eventdetail="Chrome for Developers" > Chrome for Developers </a> </li> <li class="devsite-breadcrumb-item "> <div class="devsite-breadcrumb-guillemet material-icons" aria-hidden="true"></div> <a href="https://developer.chrome.com/blog" class="devsite-breadcrumb-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Breadcrumbs" data-value="2" track-type="globalNav" track-name="breadcrumb" track-metadata-position="2" track-metadata-eventdetail="Blog" > Blog </a> </li> </ul> <devsite-thumb-rating position="header"> </devsite-thumb-rating> </div> <h1 class="devsite-page-title" tabindex="-1"> CSS containment in Chrome 52 </h1> <devsite-feature-tooltip ack-key="AckCollectionsBookmarkTooltipDismiss" analytics-category="Site-Wide Custom Events" analytics-action-show="Callout Profile displayed" analytics-action-close="Callout Profile dismissed" analytics-label="Create Collection Callout" class="devsite-page-bookmark-tooltip nocontent" dismiss-button="true" id="devsite-collections-dropdown" dismiss-button-text="Dismiss" close-button-text="Got it"> <devsite-bookmark></devsite-bookmark> <span slot="popout-heading"> Stay organized with collections </span> <span slot="popout-contents"> Save and categorize content based on your preferences. </span> </devsite-feature-tooltip> <div class="devsite-page-title-meta"><devsite-view-release-notes></devsite-view-release-notes></div> <devsite-toc class="devsite-nav" depth="2" devsite-toc-embedded > </devsite-toc> <div class="devsite-article-body clearfix "> <p><style> .wd-authors { --avatar-size: 65px; display: flex; gap: 2em; } .wd-author { display: flex; flex-wrap: wrap; gap: 1em; line-height: calc(var(--avatar-size) / 2); } .wd-author img { border-radius: 50%; height: var(--avatar-size, 65px); width: var(--avatar-size, 65px); } .dcc-authors { --avatar-size: 65px; display: flex; gap: 2em; } .dcc-author { display: flex; flex-wrap: wrap; gap: 1em; line-height: calc(var(--avatar-size) / 2); } .dcc-author img { border-radius: 50%; height: var(--avatar-size, 65px); width: var(--avatar-size, 65px); } .dcc-author__links a { margin-inline-end: 6px; } .dcc-author__links a:last-of-type { margin-inline-end: 0; } </style> <div class="dcc-authors" translate="no"> <div class="dcc-author"> <div> <span> Paul Lewis </span> <div class="dcc-author__links"> <a href="https://twitter.com/aerotwist" aria-label="Paul Lewis on X" rel="me"> <svg xmlns="http://www.w3.org/2000/svg" width="22" height="22" viewBox="0 0 300 271"> <title>X</title> <path fill="currentColor" d="m236 0h46l-101 115 118 156h-92.6l-72.5-94.8-83 94.8h-46l107-123-113-148h94.9l65.5 86.6zm-16.1 244h25.5l-165-218h-27.4z"></path> </svg></a> <a href="https://aerotwist.com/" aria-label="Paul Lewis's homepage" rel="me"> <svg xmlns="http://www.w3.org/2000/svg" width="22" height="22" viewBox="0 0 30 30"> <title>Homepage</title> <circle cx="14.5" cy="14.5" r="13.5" stroke-width="2" stroke-miterlimit="10" fill="none" stroke="currentColor" /> <ellipse cx="14.5" cy="14.5" rx="6.1" ry="13.5" stroke-width="2" stroke-miterlimit="10" fill="none" stroke="currentColor" /> <path d="M1.6 9.6h25.8M1.6 19.4h25.8" stroke-width="2" stroke-miterlimit="10" fill="none" stroke="currentColor" /> </svg></a> </div> </div> </div> </div></p> <h2 id="tldr" data-text="TL;DR" tabindex="-1">TL;DR</h2> <p>The new CSS Containment property lets developers limit the scope of the browser's styles, layout and paint work.</p> <figure> <img src="/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef.jpg" alt="CSS Containment. Before: layout takes 59.6ms. After: layout takes 0.05ms" width="800" height="363" srcset="https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_36.jpg 36w,https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_48.jpg 48w,https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_72.jpg 72w,https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_96.jpg 96w,https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_480.jpg 480w,https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_720.jpg 720w,https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_856.jpg 856w,https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_960.jpg 960w,https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_1440.jpg 1440w,https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_1920.jpg 1920w,https://developer.chrome.com/static/blog/css-containment/image/css-containment-before-dd44d7d4075ef_2880.jpg 2880w" sizes="(max-width: 840px) 100vw, 856px"> </figure> <p>It has a few values, making its syntax this:</p> <div></div><devsite-code><pre class="devsite-click-to-copy" translate="no" dir="ltr" is-upgraded syntax="CSS"><code translate="no" dir="ltr"><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nt">contain</span><span class="devsite-syntax-o">:</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nt">none</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">|</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nt">strict</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">|</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nt">content</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">|</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">[</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nt">size</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">||</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nt">layout</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">||</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nt">style</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">||</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nt">paint</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">]</span> </code></pre></devsite-code> <p>It’s in Chrome 52+ and Opera 40+ (and it has <a href="https://www.chromestatus.com/features/6522186978295808">public support from Firefox</a>), so give it a whirl and let us know how you go!</p> <h2 id="the_contain_property" data-text="The contain property" tabindex="-1">The contain property</h2> <p>When making a web app, or even a complex site, a key performance challenge is limiting the effects of styles, layout and paint. Oftentimes the <em>entirety</em> of the DOM is considered “in scope” for computation work, which can mean that attempting a self-contained “view” in a web app can prove tricky: changes in one part of the DOM can affect other parts, and there’s no way to tell the browser what should be in or out of scope.</p> <p>For example, let’s say part of your DOM looks like this:</p> <div></div><devsite-code><pre class="devsite-click-to-copy" translate="no" dir="ltr" is-upgraded syntax="HTML"><code translate="no" dir="ltr"> <section class="view"> Home </section> <section class="view"> About </section> <section class="view"> Contact </section> </code></pre></devsite-code> <p>And you append a new element to one view, which will trigger styles, layout and paint:</p> <div></div><devsite-code><pre class="devsite-click-to-copy" translate="no" dir="ltr" is-upgraded syntax="HTML"><code translate="no" dir="ltr"> <section class="view"> Home </section> <section class="view"> About <div class="newly-added-element">Check me out!</div> </section> <section class="view"> Contact </section> </code></pre></devsite-code> <p>In this case, however, the <em>whole DOM</em> is effectively in scope, meaning that style, layout, and paint calculations will have to consider <em>all the elements</em> irrespective of whether or not they were changed. The bigger the DOM, the more computation work that involves, meaning that you could well make your app unresponsive to user input.</p> <p>The good news is that modern browsers are getting really smart about limiting the scope of styles, layout, and paint work automatically, meaning that things are getting faster without you having to do anything.</p> <p>But the <em>even better</em> news is that there’s a new CSS property that hands scope controls over to developers: <strong>Containment</strong>.</p> <p>CSS Containment is a new property, with the keyword contain, which supports four values:</p> <ul> <li><code translate="no" dir="ltr">layout</code></li> <li><code translate="no" dir="ltr">paint</code></li> <li><code translate="no" dir="ltr">size</code></li> <li><code translate="no" dir="ltr">style</code></li> </ul> <p>Each of these values allows you to limit how much rendering work the browser needs to do. Let’s take a look at each in a little more detail.</p> <h3 id="layout_contain_layout" data-text="Layout (contain: layout)" tabindex="-1">Layout (contain: layout)</h3> <aside class="note"><b>Note:</b> This value turns on layout containment for the element. This ensures that the containing element is totally opaque for layout purposes; nothing outside can affect its internal layout, and vice versa. <a href="https://drafts.csswg.org/css-contain/#valdef-contain-layout">Containment spec</a></aside> <p>Layout containment is probably <em>the</em> biggest benefit of containment, along with <code translate="no" dir="ltr">contain: paint</code>.</p> <p>Layout is normally document-scoped, making it scale proportionally to the size of your DOM, so if you change an element's <code translate="no" dir="ltr">left</code> property, every single element in the DOM might need to be checked.</p> <p>Enabling containment here can potentially reduce the number of elements to just a handful, rather than the whole document, saving the browser a ton of unnecessary work and significantly improving performance.</p> <h3 id="paint_contain_paint" data-text="Paint (contain: paint)" tabindex="-1">Paint (contain: paint)</h3> <aside class="note"><b>Note:</b> This value turns on paint containment for the element. This ensures that the descendants of the containing element don’t display outside its bounds, so if an element is off-screen or otherwise not visible, its descendants are also guaranteed to be not visible. <a href="https://drafts.csswg.org/css-containment/#valdef-contain-paint">Containment spec</a></aside> <p>Scoping paint is another incredibly useful benefit of containment. Paint containment essentially clips the element in question, but it also has a few other side effects:</p> <ul> <li><strong>It acts as a containing block for absolutely positioned and fixed position elements.</strong> This means any children are positioned based on the element with <code translate="no" dir="ltr">contain: paint</code> not any other parent element like -- say -- the document.</li> <li><strong>It becomes a stacking context.</strong> This means that things like <code translate="no" dir="ltr">z-index</code> will have an effect on the element, and children will be stacked according to the new context.</li> <li><strong>It becomes a new formatting context.</strong> This means that if you have, for example, a block level element with paint containment, it will be treated as a new, <em>independent</em> layout environment. This means that layout outside of the element won’t typically affect the containing element's children.</li> </ul> <h3 id="size_contain_size" data-text="Size (contain: size)" tabindex="-1">Size (contain: size)</h3> <aside class="note"><b>Note:</b> The value turns on size containment for the element. This ensures that the containing element can be laid out without needing to examine its descendants. <a href="https://drafts.csswg.org/css-contain/#valdef-contain-size">Containment spec</a></aside> <p>What <code translate="no" dir="ltr">contain: size</code> means is that the element’s children <em>do not affect the parent’s size</em>, and that its inferred or declared dimensions will be the ones used. Consequently if you were to set <code translate="no" dir="ltr">contain: size</code> but didn’t specify dimensions for the element (either directly or via flex properties), it would be rendered at 0px by 0px!</p> <p>Size containment is really a belt-and-braces measure to ensure you don’t rely on child elements for sizing, but by itself it doesn’t offer much performance benefit.</p> <h3 id="style_contain_style" data-text="Style (contain: style)" tabindex="-1">Style (contain: style)</h3> <aside class="note"><b>Note:</b> This value turns on style containment for the element. This ensures that, for properties which can have effects on more than just an element and its descendants, those effects don’t escape the containing element. <a href="https://drafts.csswg.org/css-contain/#valdef-contain-style">Containment spec</a></aside> <p>It can be hard to predict what the effects on the DOM tree of changing an element’s styles will be back up the tree. One example of this is in something like <a href="https://developer.mozilla.org/docs/Web/CSS/CSS_Lists_and_Counters/Using_CSS_counters">CSS counters</a>, where changing a counter in a child can affect counter values of the same name used elsewhere in the document. With <code translate="no" dir="ltr">contain: style</code> set, style changes won’t get propagated back up past the containing element.</p> <p><strong>To be super clear, what <code translate="no" dir="ltr">contain: style</code> <em>doesn’t</em> provide is scoped styling as you’d get from Shadow DOM</strong>; containment here is purely about limiting the parts of the tree that are under consideration when styles are mutated, <em>not</em> when they are declared.</p> <h2 id="strict_and_content_containment" data-text="Strict and content containment" tabindex="-1">Strict and content containment</h2> <p>You can also combine keywords, such as <code translate="no" dir="ltr">contain: layout paint</code>, which will apply only those behaviors to an element. But contain also supports two additional values:</p> <ul> <li><code translate="no" dir="ltr">contain: strict</code> means the same as <code translate="no" dir="ltr">contain: size layout paint</code></li> <li><code translate="no" dir="ltr">contain: content</code> means the same as <code translate="no" dir="ltr">contain: layout paint</code></li> </ul> <p>Using strict containment is great when you know the size of the element ahead of time (or wish to reserve its dimensions), but bear in mind that if you declare strict containment <em>without</em> dimensions, because of the implied size containment, the element may be rendered as a 0px by 0px box.</p> <p>Content containment, on the other hand, offers significant scope improvements, but does not require you to know or specify the dimensions of the element ahead of time.</p> <p>Of the two, <code translate="no" dir="ltr">contain: content</code> is the one you should look to use by default. You should treat strict containment as something of a more an escape hatch when <code translate="no" dir="ltr">contain: content</code> isn’t strong enough for your needs.</p> <h2 id="let_us_know_how_you_get_on" data-text="Let us know how you get on" tabindex="-1">Let us know how you get on</h2> <p>Containment is a great way to start indicating to the browser what you intend to be kept isolated within your page. Give it a try in Chrome 52+ and let us know how you get on!</p> <h3 id="useful_links" data-text="Useful links" tabindex="-1">Useful links</h3> <ul> <li><a href="https://drafts.csswg.org/css-contain/">CSS Containment Spec</a></li> <li><a href="https://www.chromestatus.com/features/6522186978295808">Containment on Chrome Status</a></li> </ul> </div> <devsite-thumb-rating position="footer"> </devsite-thumb-rating> <div class="devsite-floating-action-buttons"> </div> </article> <devsite-content-footer class="nocontent"> <p>Except as otherwise noted, the content of this page is licensed under the <a href="https://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution 4.0 License</a>, and code samples are licensed under the <a href="https://www.apache.org/licenses/LICENSE-2.0">Apache 2.0 License</a>. For details, see the <a href="https://developers.google.com/site-policies">Google Developers Site Policies</a>. 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