Time to First Byte (TTFB) | Articles

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href="/explore/ai" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: AI" track-name="ai" data-category="Site-Wide Custom Events" data-label="Responsive Tab: AI" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > AI </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/how-to-optimize-inp" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Optimize Interaction to Next Paint (INP)" track-name="optimize interaction to next paint (inp)" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Optimize Interaction to Next Paint (INP)" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Optimize Interaction to Next Paint (INP) </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/progressive-web-apps" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Progressive Web Apps" track-name="progressive web apps" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Progressive Web Apps" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Progressive Web Apps </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/accessibility" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Accessible to all" track-name="accessible to all" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Accessible to all" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Accessible to all </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/reliable" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Network reliability" track-name="network reliability" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Network reliability" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Network reliability </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/secure" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Safe and secure" track-name="safe and secure" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Safe and secure" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Safe and secure </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/discoverable" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Easily discoverable" track-name="easily discoverable" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Easily discoverable" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Easily discoverable </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/payments" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Web Payments" track-name="web payments" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Web Payments" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Web Payments </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/media" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Media" track-name="media" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Media" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Media </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/devices" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Devices" track-name="devices" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Devices" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Devices </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/animations" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Animations" track-name="animations" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Animations" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Animations </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/identity" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Identity" track-name="identity" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Identity" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Identity </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/webassembly" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: WebAssembly" track-name="webassembly" data-category="Site-Wide Custom Events" data-label="Responsive Tab: WebAssembly" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > WebAssembly </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/test-automation" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Test automation" track-name="test automation" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Test automation" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Test automation </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/react" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: React" track-name="react" data-category="Site-Wide Custom Events" data-label="Responsive Tab: React" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > React </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/angular" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Angular" track-name="angular" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Angular" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Angular </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/explore/mini-apps" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Mini apps" track-name="mini apps" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Mini apps" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Mini apps </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> </ul> </li> <li class="devsite-nav-item"> <a href="/patterns" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Tab: Patterns" track-name="patterns" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Patterns" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Patterns </span> </a> </li> <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: Case studies" track-name="case studies" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Case studies" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Case studies </span> </a> </li> </ul> </div> <div class="devsite-mobile-nav-bottom"> <ul class="devsite-nav-list" menu="_book"> <li class="devsite-nav-item devsite-nav-heading"><div class="devsite-nav-title devsite-nav-title-no-path"> <span class="devsite-nav-text" tooltip>Introduction</span> </div></li> <li class="devsite-nav-item"><a href="/articles/user-centric-performance-metrics" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /articles/user-centric-performance-metrics" track-type="bookNav" track-name="click" track-metadata-eventdetail="/articles/user-centric-performance-metrics" ><span class="devsite-nav-text" tooltip>User-centric performance metrics</span></a></li> <li class="devsite-nav-item devsite-nav-heading"><div class="devsite-nav-title devsite-nav-title-no-path"> <span class="devsite-nav-text" tooltip>Important metrics to measure</span> </div></li> <li class="devsite-nav-item"><a href="/articles/lcp" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /articles/lcp" track-type="bookNav" track-name="click" track-metadata-eventdetail="/articles/lcp" ><span class="devsite-nav-text" tooltip>Largest Contentful Paint (LCP)</span></a></li> <li class="devsite-nav-item"><a href="/articles/cls" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /articles/cls" track-type="bookNav" track-name="click" track-metadata-eventdetail="/articles/cls" ><span class="devsite-nav-text" tooltip>Cumulative Layout Shift (CLS)</span></a></li> <li class="devsite-nav-item"><a href="/articles/inp" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /articles/inp" track-type="bookNav" track-name="click" track-metadata-eventdetail="/articles/inp" ><span class="devsite-nav-text" tooltip>Interaction to Next Paint (INP)</span></a></li> <li class="devsite-nav-item"><a href="/articles/ttfb" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /articles/ttfb" track-type="bookNav" track-name="click" track-metadata-eventdetail="/articles/ttfb" ><span class="devsite-nav-text" tooltip>Time to First Byte (TTFB)</span></a></li> <li class="devsite-nav-item"><a href="/articles/fcp" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /articles/fcp" track-type="bookNav" track-name="click" track-metadata-eventdetail="/articles/fcp" ><span class="devsite-nav-text" tooltip>First Contentful Paint (FCP)</span></a></li> <li class="devsite-nav-item"><a href="/articles/tbt" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /articles/tbt" track-type="bookNav" track-name="click" track-metadata-eventdetail="/articles/tbt" ><span class="devsite-nav-text" tooltip>Total Blocking Time (TBT)</span></a></li> <li class="devsite-nav-item devsite-nav-heading"><div class="devsite-nav-title devsite-nav-title-no-path"> <span class="devsite-nav-text" tooltip>Define your own metrics</span> </div></li> <li class="devsite-nav-item"><a href="/articles/custom-metrics" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /articles/custom-metrics" track-type="bookNav" track-name="click" track-metadata-eventdetail="/articles/custom-metrics" ><span class="devsite-nav-text" tooltip>Custom metrics</span></a></li> </ul> </div> </div> </nav> </devsite-book-nav> <section id="gc-wrapper"> <main role="main" class="devsite-main-content" has-book-nav 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://web.dev/" 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="" > Home </a> </li> <li class="devsite-breadcrumb-item "> <div class="devsite-breadcrumb-guillemet material-icons" aria-hidden="true"></div> <a href="https://web.dev/articles" 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="Articles" > Articles </a> </li> <li class="devsite-breadcrumb-item "> <div class="devsite-breadcrumb-guillemet material-icons" aria-hidden="true"></div> <a href="https://web.dev/explore" class="devsite-breadcrumb-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Breadcrumbs" data-value="3" track-type="globalNav" track-name="breadcrumb" track-metadata-position="3" track-metadata-eventdetail="" > Explore </a> </li> <li class="devsite-breadcrumb-item "> <div class="devsite-breadcrumb-guillemet material-icons" aria-hidden="true"></div> <a href="https://web.dev/explore/metrics" class="devsite-breadcrumb-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Breadcrumbs" data-value="4" track-type="globalNav" track-name="breadcrumb" track-metadata-position="4" track-metadata-eventdetail="" > Metrics </a> </li> </ul> <devsite-thumb-rating position="header"> </devsite-thumb-rating> </div> <h1 class="devsite-page-title" tabindex="-1"> Time to First Byte (TTFB) </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> <div class="wd-authors" translate="no"> <div class="wd-author"> <img class="devsite-landing-row-item-icon" alt="Jeremy Wagner" src="https://web.dev/images/authors/jlwagner-v3.jpg" decoding="async" height="64" loading="lazy" width="64"> <div> <span> Jeremy Wagner </span> <div class="wd-author__links"> <a href="https://github.com/malchata" aria-label="Jeremy Wagner on GitHub" rel="me"> <svg xmlns="http://www.w3.org/2000/svg" width="22" height="22" viewBox="0 0 32.6 31.8"> <title>GitHub</title> <path d="M16.3 0C7.3 0 0 7.3 0 16.3c0 7.2 4.7 13.3 11.1 15.5.8.1 1.1-.4 1.1-.8v-2.8c-4.5 1-5.5-2.2-5.5-2.2-.7-1.9-1.8-2.4-1.8-2.4-1.5-1 .1-1 .1-1 1.6.1 2.5 1.7 2.5 1.7 1.5 2.5 3.8 1.8 4.7 1.4.1-1.1.6-1.8 1-2.2-3.6-.4-7.4-1.8-7.4-8.1 0-1.8.6-3.2 1.7-4.4-.1-.3-.7-2 .2-4.2 0 0 1.4-.4 4.5 1.7 1.3-.4 2.7-.5 4.1-.5 1.4 0 2.8.2 4.1.5 3.1-2.1 4.5-1.7 4.5-1.7.9 2.2.3 3.9.2 4.3 1 1.1 1.7 2.6 1.7 4.4 0 6.3-3.8 7.6-7.4 8 .6.5 1.1 1.5 1.1 3V31c0 .4.3.9 1.1.8 6.5-2.2 11.1-8.3 11.1-15.5C32.6 7.3 25.3 0 16.3 0z" fill-rule="evenodd" clip-rule="evenodd" fill="currentColor" /> </svg></a> <a href="https://www.linkedin.com/in/malchata" aria-label="Jeremy Wagner on LinkedIn" rel="me"> <svg xmlns="http://www.w3.org/2000/svg" width="22" height="22" viewBox="0 0 200 200"> <title>LinkedIn</title> <path d="M185.2 0H14.8C6.6 0 0 6.4 0 14.3v171.3c0 7.9 6.6 14.3 14.8 14.3h170.4c8.1 0 14.8-6.4 14.8-14.3V14.3C199.9 6.4 193.3 0 185.2 0zM60.6 167.3H30.4V77.1h30.2v90.2zM45.5 64.8h-.2c-10.1 0-16.7-6.9-16.7-15.6 0-8.8 6.7-15.6 17.1-15.6 10.3 0 16.7 6.7 16.9 15.6 0 8.6-6.5 15.6-17.1 15.6zm124 102.5h-30.2V119c0-12.1-4.4-20.4-15.3-20.4-8.4 0-13.3 5.6-15.5 11-.8 1.9-1 4.6-1 7.3v50.4H77.3s.4-81.8 0-90.3h30.2v12.8c4-6.1 11.2-14.9 27.2-14.9 19.9 0 34.8 12.9 34.8 40.6v51.8zm-62.2-77.1c0-.1.1-.2.2-.3v.3h-.2z" fill="currentColor" /> </svg></a> <a href="https://jlwagner.net/" aria-label="Jeremy Wagner'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 class="wd-author"> <img class="devsite-landing-row-item-icon" alt="Barry Pollard" src="https://web.dev/images/authors/tunetheweb.jpg" decoding="async" height="64" loading="lazy" width="64"> <div> <span> Barry Pollard </span> <div class="wd-author__links"> <a href="https://twitter.com/tunetheweb" aria-label="Barry Pollard 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://github.com/tunetheweb" aria-label="Barry Pollard on GitHub" rel="me"> <svg xmlns="http://www.w3.org/2000/svg" width="22" height="22" viewBox="0 0 32.6 31.8"> <title>GitHub</title> <path d="M16.3 0C7.3 0 0 7.3 0 16.3c0 7.2 4.7 13.3 11.1 15.5.8.1 1.1-.4 1.1-.8v-2.8c-4.5 1-5.5-2.2-5.5-2.2-.7-1.9-1.8-2.4-1.8-2.4-1.5-1 .1-1 .1-1 1.6.1 2.5 1.7 2.5 1.7 1.5 2.5 3.8 1.8 4.7 1.4.1-1.1.6-1.8 1-2.2-3.6-.4-7.4-1.8-7.4-8.1 0-1.8.6-3.2 1.7-4.4-.1-.3-.7-2 .2-4.2 0 0 1.4-.4 4.5 1.7 1.3-.4 2.7-.5 4.1-.5 1.4 0 2.8.2 4.1.5 3.1-2.1 4.5-1.7 4.5-1.7.9 2.2.3 3.9.2 4.3 1 1.1 1.7 2.6 1.7 4.4 0 6.3-3.8 7.6-7.4 8 .6.5 1.1 1.5 1.1 3V31c0 .4.3.9 1.1.8 6.5-2.2 11.1-8.3 11.1-15.5C32.6 7.3 25.3 0 16.3 0z" fill-rule="evenodd" clip-rule="evenodd" fill="currentColor" /> </svg></a> <a href="https://webperf.social/@tunetheweb" aria-label="Barry Pollard on Mastodon" rel="me"> <svg xmlns="http://www.w3.org/2000/svg" width="22" height="22" viewBox="0 0 16 16"> <title>Mastodon</title> <path fill="currentColor" d="M 15.659 9.592 C 15.424 10.72 13.553 11.956 11.404 12.195 C 10.283 12.32 9.18 12.434 8.003 12.384 C 6.079 12.302 4.56 11.956 4.56 11.956 C 4.56 12.13 4.572 12.297 4.595 12.452 C 4.845 14.224 6.478 14.33 8.025 14.379 C 9.586 14.429 10.976 14.02 10.976 14.02 L 11.04 15.337 C 11.04 15.337 9.948 15.884 8.003 15.984 C 6.93 16.039 5.598 15.959 4.047 15.576 C 0.683 14.746 0.104 11.4 0.015 8.006 C -0.012 6.998 0.005 6.048 0.005 5.253 C 0.005 1.782 2.443 0.765 2.443 0.765 C 3.672 0.238 5.782 0.017 7.975 0 L 8.029 0 C 10.221 0.017 12.332 0.238 13.561 0.765 C 13.561 0.765 15.999 1.782 15.999 5.253 C 15.999 5.253 16.03 7.814 15.659 9.592 Z M 13.124 5.522 L 13.124 9.725 L 11.339 9.725 L 11.339 5.646 C 11.339 4.786 10.951 4.35 10.175 4.35 C 9.317 4.35 8.887 4.867 8.887 5.891 L 8.887 8.124 L 7.113 8.124 L 7.113 5.891 C 7.113 4.867 6.683 4.35 5.825 4.35 C 5.049 4.35 4.661 4.786 4.661 5.646 L 4.661 9.725 L 2.876 9.725 L 2.876 5.522 C 2.876 4.663 3.111 3.981 3.582 3.476 C 4.067 2.971 4.703 2.712 5.493 2.712 C 6.406 2.712 7.098 3.039 7.555 3.695 L 8 4.39 L 8.445 3.695 C 8.902 3.039 9.594 2.712 10.507 2.712 C 11.297 2.712 11.933 2.971 12.418 3.476 C 12.889 3.981 13.124 4.663 13.124 5.522 Z" style="stroke:none;stroke-miterlimit:10;fill-rule:evenodd;"></path> </svg></a> <a href="https://www.tunetheweb.com" aria-label="Barry Pollard'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" 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aria-hidden="true"> 35 </span> </li> <li data-support="yes"> <img alt="Safari: 11." src="data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink' width='24' height='24' viewBox='195 190 135 135'%3E%3Cdefs%3E%3ClinearGradient id='s-a' x1='132.6' x2='134.4' y1='111.7' y2='-105.3' xlink:href='%23s-b'%3E%3Cstop offset='0' stop-color='%23d2d2d2' /%3E%3Cstop offset='.5' stop-color='%23f2f2f2' /%3E%3Cstop offset='1' stop-color='%23fff' /%3E%3C/linearGradient%3E%3ClinearGradient id='s-b' gradientUnits='userSpaceOnUse' /%3E%3ClinearGradient id='s-c' x1='65.4' x2='67.4' y1='115.7' y2='17.1' xlink:href='%23s-b'%3E%3Cstop offset='0' stop-color='%23005ad5' /%3E%3Cstop offset='.2' stop-color='%230875f0' /%3E%3Cstop offset='.3' stop-color='%23218cee' /%3E%3Cstop offset='.6' stop-color='%2327a5f3' /%3E%3Cstop offset='.8' stop-color='%2325aaf2' /%3E%3Cstop offset='1' stop-color='%2321aaef' /%3E%3C/linearGradient%3E%3ClinearGradient id='s-d' x1='158.7' 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/%3E%3Ccircle cx='-69.9' cy='69.3' fill='url(%23s-i)' transform='translate(138 -2)' r='54' /%3E%3C/g%3E%3Cellipse cx='120' cy='14.2' fill='url(%23s-j)' rx='93.1' ry='93.7' transform='matrix(.58 0 0 .58 192 250)' /%3E%3Cg transform='matrix(.58 0 0 .57 197 182)'%3E%3Cpath fill='%23cac7c8' d='M46 192h1l72-48-7-9-66 57Z' /%3E%3Cpath fill='%23fbfffc' d='M46 191v1l66-57-7-9-59 65Z' /%3E%3Cpath fill='url(%23s-d)' d='m119 144-7-9 66-57-59 66Z' /%3E%3Cpath fill='%23fb645c' d='m105 126 7 9 66-57-1-1-72 49Z' /%3E%3C/g%3E%3Cpath stroke='%23fff' stroke-linecap='round' stroke-miterlimit='1' stroke-width='1.3' d='m287 278 3-2m-12-17 8-2m-8-3h4m-4-13 8 2m-8 3h4m-1-13 7 3m-4-11 7 4m-2-11 6 6m0-12 6 7m1-11 4 6m4-10 3 7m5-9 2 7m15-7-1 7m10-5-3 7m11-4-4 7m11-2-5 6m16 7-7 4m10 4-7 3m10 6-8 1m8 16-8-2m5 10-7-3m4 11-7-4m2 11-6-5m0 11-5-6m-2 11-4-7m-4 11-3-8m-6 10-1-8m-16 8 2-8m-10 5 3-7m-11 4 4-7m-11 2 5-6m-8 3 3-3m4 8 2-3m5 8 2-4m6 7 1-4m8 5v-4m8 4v-4m9 3-1-4m9 1-2-4m9 0-2-4m9-2-3-3m8-4-3-2m8-5-4-2m7-6-4-1m5-8h-4m4-8h-4m3-9-4 1m1-9-4 2m-1-9-3 2m-2-9-3 3m-4-8-2 3m-5-8-2 4m-6-6-1 3m-8-5v4m-8-4v4m-9-2 1 3m-9 0 2 3m-9 1 2 3m-9 2 3 3m-8 4 3 2m-8 5 4 2m-7 6 4 1m-4 25 4-1m-2 5 7-3m-6 7 4-2m-2 6 7-4m-13-21h8m41-41v-8m0 99v-8m49-42h-8' transform='translate(-65 8)' /%3E%3C/svg%3E" > <span aria-hidden="true"> 11 </span> </li> </ul> <p><a href="https://developer.mozilla.org/docs/Web/API/PerformanceResourceTiming/responseStart">Source</a></p> </div> </p> <aside class="note"> <b>Note:</b> Time to First Byte (TTFB) is a foundational metric for measuring connection setup time and web server responsiveness in both the lab and the field. It helps identify when a web server is too slow to respond to requests. In the case of navigation requests鈥攖hat is, requests for an HTML document鈥攊t precedes every other meaningful loading performance metric. </aside> <h2 id="what_is_ttfb" data-text="What is TTFB?" tabindex="-1">What is TTFB?</h2> <p>TTFB is a metric that measures the time between the request for a resource and when the first byte of a response begins to arrive.</p> <figure> <img src="/static/articles/ttfb/image/performance-navigation-timing-timestamp-diagram.svg" alt="A visualization of network request timings. The timings from left to right are Redirect, Service Worker Init, Service Worker Fetch event, HTTP Cache, DNS, TCP, Request, Early Hints (103), Response (which overlaps with Prompt for Unload), Processing, and Load. The associated timings are redirectStart and redirectEnd, fetchStart, domainLookupStart, domainLookupEnd, connectStart, secureConnectionStart, connectEnd, requestStart, interimResponseStart, responseStart, unloadEventStart, unloadEventEnd, responseEnd, domInteractive, domContentLoadedEventStart, domContentLoadedEventEnd, domComplete, loadEventStart, and loadEventEnd." width="800" height="319"> <figcaption class="wd-caption"> A diagram of network request phases and their associated timings. TTFB measures the elapsed time between <code translate="no" dir="ltr">startTime</code> and <code translate="no" dir="ltr">responseStart</code>. </figcaption> </figure> <p>TTFB is the sum of the following request phases:</p> <ul> <li>Redirect time</li> <li>Service worker startup time (if applicable)</li> <li>DNS lookup</li> <li>Connection and TLS negotiation</li> <li>Request, up until the point at which the first byte of the response has arrived</li> </ul> <p>Reducing latency in connection setup time and on the backend can lower your TTFB.</p> <h3 id="other-definitions" data-text="Other definitions of TTFB" tabindex="-1">Other definitions of TTFB</h3> <p>The previous definition is the conventional definition but with the introduction of <a href="https://developer.chrome.com/docs/web-platform/early-hints">Early Hints</a> what is considered the "first byte" is up for debate. The <a href="https://developer.mozilla.org/docs/Web/API/PerformanceResourceTiming/firstInterimResponseStart"><code translate="no" dir="ltr">firstInterimResponseStart</code></a> is an new additional timing entry to <code translate="no" dir="ltr">responseStart</code> to differentiate between these but this is only supported in Chrome and Chromium-based browsers. Therefore some browsers and tools (<a href="https://developer.chrome.com/docs/crux/methodology/metrics#ttfb-metric">including CrUX</a>) measure until the first bytes are received including Early Hints.</p> <p>Early Hints is just a newer example of responding early. Some servers allow flushing of the document response to happen before the main body is available鈥攅ither with just the HTTP headers, or with the <code translate="no" dir="ltr"><head></code> element, both of which could be considered similar in effect to Early Hints and so also cloud the definition of what TTFB measures.</p> <p>As a measure of when the "first bytes" of actionable data for the document are received by the browser, all these definitions could be considered valid, There is real value in sending back data early if the full response is going to take some more time. What is most important is to understand what the measure the tool you are using measures and how that is affected by the platform being measured. This does make it difficult to compare TTFB across different platforms or technologies depending on what features they use, and how that impacts the TTFB measurement being used.</p> <p>TTFB is also often considered as an indicator of server or host response time. However, it will be affected by factors outside of that direct control such as redirect time, whether it is served from a cache hit by a CDN or has to make a potentially longer journey back to an origin server. This is particularly apparent in field data鈥攍ab testing typically is less affected by these factors since the end URL is usually tested and often repeatedly negating caching changes. Lighthouse reports <a href="https://developer.chrome.com/docs/lighthouse/performance/server-response-time"><em>server response time</em></a> rather than TTFB to make this clearer but other lab tools may not.</p> <h3 id="good-ttfb-score" data-text="What is a good TTFB score?" tabindex="-1">What is a good TTFB score?</h3> <p>Because TTFB precedes <a href="/articles/user-centric-performance-metrics">user-centric metrics</a> such as <a href="/articles/fcp">First Contentful Paint (FCP)</a> and <a href="/articles/lcp">Largest Contentful Paint (LCP)</a>, it's recommended that your server responds to navigation requests quickly enough so that the <strong>75th percentile</strong> of users experience an <a href="/articles/fcp#what_is_a_good_fcp_score">FCP within the "good" threshold</a>. As a rough guide, most sites should strive to have a TTFB of <strong>0.8 seconds</strong> or less.</p> <figure> <picture> <source srcset="https://web.dev/static/articles/ttfb/image/good-ttfb-values.svg" media="(min-width: 640px)" width="800" height="200"> <img src="/static/articles/ttfb/image/good-ttfb-values-are-08-ca73d93f5df2d.svg" alt="Good TTFB values are 0.8 seconds or less, poor values are greater than 1.8 seconds, and anything in between needs improvement" width="640" height="480"> </picture> <figcaption class="wd-caption"> Good TTFB values are 0.8 seconds or less, and poor values are greater than 1.8 seconds. </figcaption> </figure> <aside class="key-point"> <p> <b>Key point:</b> Because TTFB isn't a <a href="/articles/vitals">Core Web Vitals</a> metric, it's not absolutely necessary that sites meet the "good" TTFB threshold, provided that it doesn't impede their ability to score well on the metrics that matter. </p> <p> Websites vary in how they deliver content. A low TTFB is crucial for getting markup out to the client as soon as possible. However, if a website delivers the initial markup quickly, but that markup then requires JavaScript to populate it with meaningful content鈥攁s is the the case with Single Page Applications (SPAs)鈥攖hen achieving the lowest possible TTFB is especially important so that the client-rendering of markup can occur sooner. </p> <p> Conversely, a server-rendered site that does not require as much client-side work could have a higher TTFB, but better FCP and LCP values than an entirely client-rendered experience. This is why the TTFB thresholds are a "rough guide", and will need to be weighed against how your site delivers its core content. </p> </aside> <h2 id="measure-ttfb" data-text="How to measure TTFB" tabindex="-1">How to measure TTFB</h2> <p>TTFB can be measured in <a href="/articles/user-centric-performance-metrics#in_the_lab">the lab</a> or in <a href="/articles/user-centric-performance-metrics#in_the_field">the field</a> in the following ways.</p> <h3 id="field_tools" data-text="Field tools" tabindex="-1">Field tools</h3> <ul> <li><a href="https://developer.chrome.com/docs/crux">Chrome User Experience Report</a></li> <li><a href="https://github.com/GoogleChrome/web-vitals"><code translate="no" dir="ltr">web-vitals</code> JavaScript library</a></li> </ul> <h3 id="lab_tools" data-text="Lab tools" tabindex="-1">Lab tools</h3> <ul> <li>In the <a href="https://developer.chrome.com/docs/devtools/network">network panel</a> of Chrome's DevTools</li> <li><a href="https://www.webpagetest.org/">WebPageTest</a></li> </ul> <h3 id="measure-in-javascript" data-text="Measure TTFB in JavaScript" tabindex="-1">Measure TTFB in JavaScript</h3> <p>You can measure the TTFB of <a href="https://developer.mozilla.org/docs/Web/API/Request/mode">navigation requests</a> in the browser with the <a href="https://developer.mozilla.org/docs/Web/API/Navigation_timing_API">Navigation Timing API</a>. The following example shows how to create a <a href="https://developer.mozilla.org/docs/Web/API/PerformanceObserver"><code translate="no" dir="ltr">PerformanceObserver</code></a> that listens for a <code translate="no" dir="ltr">navigation</code> entry and logs it to the console:</p> <div></div><devsite-code><pre class="devsite-click-to-copy" translate="no" dir="ltr" is-upgraded syntax="JavaScript"><code translate="no" dir="ltr"><span class="devsite-syntax-ow">new</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">PerformanceObserver</span><span class="devsite-syntax-p">((</span><span class="devsite-syntax-nx">entryList</span><span class="devsite-syntax-p">)</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">=</span>><span class="devsite-syntax-w"> </span><span class="devsite-syntax-p">{</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-kd">const</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-p">[</span><span class="devsite-syntax-nx">pageNav</span><span class="devsite-syntax-p">]</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">=</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">entryList</span><span class="devsite-syntax-p">.</span><span class="devsite-syntax-nx">getEntriesByType</span><span class="devsite-syntax-p">(</span><span class="devsite-syntax-s1">'navigation'</span><span class="devsite-syntax-p">);</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">console</span><span class="devsite-syntax-p">.</span><span class="devsite-syntax-nx">log</span><span class="devsite-syntax-p">(</span><span class="devsite-syntax-sb">`TTFB: </span><span class="devsite-syntax-si">${</span><span class="devsite-syntax-nx">pageNav</span><span class="devsite-syntax-p">.</span><span class="devsite-syntax-nx">responseStart</span><span class="devsite-syntax-si">}</span><span class="devsite-syntax-sb">`</span><span class="devsite-syntax-p">);</span> <span class="devsite-syntax-p">}).</span><span class="devsite-syntax-nx">observe</span><span class="devsite-syntax-p">({</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">type</span><span class="devsite-syntax-o">:</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-s1">'navigation'</span><span class="devsite-syntax-p">,</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">buffered</span><span class="devsite-syntax-o">:</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-kc">true</span> <span class="devsite-syntax-p">});</span> </code></pre></devsite-code> <p>The <a href="https://github.com/GoogleChrome/web-vitals"><code translate="no" dir="ltr">web-vitals</code> JavaScript library</a> can also measure TTFB in the browser more succinctly:</p> <div></div><devsite-code><pre class="devsite-click-to-copy" translate="no" dir="ltr" is-upgraded syntax="JavaScript"><code translate="no" dir="ltr"><span class="devsite-syntax-k">import</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-p">{</span><span class="devsite-syntax-nx">onTTFB</span><span class="devsite-syntax-p">}</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-kr">from</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-s1">'web-vitals'</span><span class="devsite-syntax-p">;</span> <span class="devsite-syntax-c1">// Measure and log TTFB as soon as it's available.</span> <span class="devsite-syntax-nx">onTTFB</span><span class="devsite-syntax-p">(</span><span class="devsite-syntax-nx">console</span><span class="devsite-syntax-p">.</span><span class="devsite-syntax-nx">log</span><span class="devsite-syntax-p">);</span> </code></pre></devsite-code> <h3 id="measure-resource-requests" data-text="Measure resource requests" tabindex="-1">Measure resource requests</h3> <p>TTFB applies to <em>all</em> requests, not just navigation requests. In particular, resources hosted on cross-origin servers can introduce latency due to the need to set up connections to those servers. To measure TTFB for resources in the field, use the <a href="https://developer.mozilla.org/docs/Web/API/Resource_Timing_API/Using_the_Resource_Timing_API">Resource Timing API</a> within a <code translate="no" dir="ltr">PerformanceObserver</code>:</p> <div></div><devsite-code><pre class="devsite-click-to-copy" translate="no" dir="ltr" is-upgraded syntax="JavaScript"><code translate="no" dir="ltr"><span class="devsite-syntax-ow">new</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">PerformanceObserver</span><span class="devsite-syntax-p">((</span><span class="devsite-syntax-nx">entryList</span><span class="devsite-syntax-p">)</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">=</span>><span class="devsite-syntax-w"> </span><span class="devsite-syntax-p">{</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-kd">const</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">entries</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-o">=</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">entryList</span><span class="devsite-syntax-p">.</span><span class="devsite-syntax-nx">getEntries</span><span class="devsite-syntax-p">();</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-k">for</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-p">(</span><span class="devsite-syntax-kd">const</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">entry</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-k">of</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">entries</span><span class="devsite-syntax-p">)</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-p">{</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-c1">// Some resources may have a responseStart value of 0, due</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-c1">// to the resource being cached, or a cross-origin resource</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-c1">// being served without a Timing-Allow-Origin header set.</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-k">if</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-p">(</span><span class="devsite-syntax-nx">entry</span><span class="devsite-syntax-p">.</span><span class="devsite-syntax-nx">responseStart</span><span class="devsite-syntax-w"> > </span><span class="devsite-syntax-mf">0</span><span class="devsite-syntax-p">)</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-p">{</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">console</span><span class="devsite-syntax-p">.</span><span class="devsite-syntax-nx">log</span><span class="devsite-syntax-p">(</span><span class="devsite-syntax-sb">`TTFB: </span><span class="devsite-syntax-si">${</span><span class="devsite-syntax-nx">entry</span><span class="devsite-syntax-p">.</span><span class="devsite-syntax-nx">responseStart</span><span class="devsite-syntax-si">}</span><span class="devsite-syntax-sb">`</span><span class="devsite-syntax-p">,</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">entry</span><span class="devsite-syntax-p">.</span><span class="devsite-syntax-nx">name</span><span class="devsite-syntax-p">);</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-p">}</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-p">}</span> <span class="devsite-syntax-p">}).</span><span class="devsite-syntax-nx">observe</span><span class="devsite-syntax-p">({</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">type</span><span class="devsite-syntax-o">:</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-s1">'resource'</span><span class="devsite-syntax-p">,</span> <span class="devsite-syntax-w"> </span><span class="devsite-syntax-nx">buffered</span><span class="devsite-syntax-o">:</span><span class="devsite-syntax-w"> </span><span class="devsite-syntax-kc">true</span> <span class="devsite-syntax-p">});</span> </code></pre></devsite-code> <p>The previous code snippet is similar to the one used to measure the TTFB for a navigation request, except instead of querying for <code translate="no" dir="ltr">'navigation'</code> entries, you query for <code translate="no" dir="ltr">'resource'</code> entries instead. It also accounts for the fact that some resources loaded from the primary origin may return a value of <code translate="no" dir="ltr">0</code>, since the connection is already open, or a resource is instantaneously retrieved from a cache.</p> <aside class="tip"> TTFB for cross-origin requests won't be measurable in the field if cross-origin servers don't set a <a href="https://developer.mozilla.org/docs/Web/HTTP/Headers/Timing-Allow-Origin"><code translate="no" dir="ltr">Timing-Allow-Origin</code> header</a>. </aside> <h2 id="how_to_improve_ttfb" data-text="How to improve TTFB" tabindex="-1">How to improve TTFB</h2> <p>For guidance on improving your site's TTFB, see our in-depth guide to <a href="/articles/optimize-ttfb">optimizing TTFB</a>.</p> </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>. 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