CINXE.COM

<!doctype html><html lang="en-US" prefix="og: https://ogp.me/ns#"><head><meta charSet="utf-8"/><meta name="viewport" content="width=device-width,initial-scale=1"/><link rel="icon" href="https://developer.mozilla.org/favicon-48x48.bc390275e955dacb2e65.png"/><link rel="apple-touch-icon" href="https://developer.mozilla.org/apple-touch-icon.528534bba673c38049c2.png"/><meta name="theme-color" content="#ffffff"/><link rel="manifest" href="https://developer.mozilla.org/manifest.f42880861b394dd4dc9b.json"/><link rel="search" type="application/opensearchdescription+xml" href="/opensearch.xml" title="MDN Web Docs"/><title>Connection management in HTTP/1.x - HTTP | MDN</title><link rel="alternate" title="Verbindungsmanagement in HTTP/1.x" href="https://developer.mozilla.org/de/docs/Web/HTTP/Connection_management_in_HTTP_1.x" hrefLang="de"/><link rel="alternate" title="Gestión de la conexión en HTTP/1.x" href="https://developer.mozilla.org/es/docs/Web/HTTP/Connection_management_in_HTTP_1.x" hrefLang="es"/><link rel="alternate" title="HTTP/1.x のコネクション管理" href="https://developer.mozilla.org/ja/docs/Web/HTTP/Connection_management_in_HTTP_1.x" hrefLang="ja"/><link rel="alternate" title="HTTP/1.x의 커넥션 관리" href="https://developer.mozilla.org/ko/docs/Web/HTTP/Connection_management_in_HTTP_1.x" hrefLang="ko"/><link rel="alternate" title="Gerenciamento de Conexão em HTTP/1.x" href="https://developer.mozilla.org/pt-BR/docs/Web/HTTP/Connection_management_in_HTTP_1.x" hrefLang="pt"/><link rel="alternate" title="Connection management in HTTP/1.x" href="https://developer.mozilla.org/ru/docs/Web/HTTP/Connection_management_in_HTTP_1.x" hrefLang="ru"/><link rel="alternate" title="HTTP/1.x 的连接管理" href="https://developer.mozilla.org/zh-CN/docs/Web/HTTP/Connection_management_in_HTTP_1.x" hrefLang="zh"/><link rel="alternate" title="Connection management in HTTP/1.x" href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x" hrefLang="en"/><link rel="preload" as="font" type="font/woff2" href="/static/media/Inter.var.c2fe3cb2b7c746f7966a.woff2" crossorigin=""/><link rel="alternate" type="application/rss+xml" title="MDN Blog RSS Feed" href="https://developer.mozilla.org/en-US/blog/rss.xml" hrefLang="en"/><meta name="description" content="Connection management is a key topic in HTTP: opening and maintaining connections largely impacts the performance of websites and Web applications. In HTTP/1.x, there are several models: short-lived connections, persistent connections, and HTTP pipelining."/><meta property="og:url" content="https://developer.mozilla.org/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x"/><meta property="og:title" content="Connection management in HTTP/1.x - HTTP | MDN"/><meta property="og:type" content="website"/><meta property="og:locale" content="en_US"/><meta property="og:description" content="Connection management is a key topic in HTTP: opening and maintaining connections largely impacts the performance of websites and Web applications. In HTTP/1.x, there are several models: short-lived connections, persistent connections, and HTTP pipelining."/><meta property="og:image" content="https://developer.mozilla.org/mdn-social-share.d893525a4fb5fb1f67a2.png"/><meta property="og:image:type" content="image/png"/><meta property="og:image:height" content="1080"/><meta property="og:image:width" content="1920"/><meta property="og:image:alt" content="The MDN Web Docs logo, featuring a blue accent color, displayed on a solid black background."/><meta property="og:site_name" content="MDN Web Docs"/><meta name="twitter:card" content="summary_large_image"/><meta name="twitter:creator" content="MozDevNet"/><link rel="canonical" href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x"/><style media="print">.article-actions-container,.document-toc-container,.language-menu,.main-menu-toggle,.on-github,.page-footer,.place,.sidebar,.top-banner,.top-navigation-main,ul.prev-next{display:none!important}.main-page-content,.main-page-content pre{padding:2px}.main-page-content pre{border-left-width:2px}</style><script src="/static/js/gtag.js" defer=""></script><script defer="" src="/static/js/main.5e889624.js"></script><link href="/static/css/main.26c64ea7.css" rel="stylesheet"/></head><body><script>if(document.body.addEventListener("load",(t=>{t.target.classList.contains("interactive")&&t.target.setAttribute("data-readystate","complete")}),{capture:!0}),window&&document.documentElement){const t={light:"#ffffff",dark:"#1b1b1b"};try{const e=window.localStorage.getItem("theme");e&&(document.documentElement.className=e,document.documentElement.style.backgroundColor=t[e]);const o=window.localStorage.getItem("nop");o&&(document.documentElement.dataset.nop=o)}catch(t){console.warn("Unable to read theme from localStorage",t)}}</script><div id="root"><ul id="nav-access" class="a11y-nav"><li><a id="skip-main" href="#content">Skip to main content</a></li><li><a id="skip-search" href="#top-nav-search-input">Skip to search</a></li><li><a id="skip-select-language" href="#languages-switcher-button">Skip to select language</a></li></ul><div class="page-wrapper category-http document-page"><div class="top-banner loading"><section class="place top container"></section></div><div class="sticky-header-container"><header class="top-navigation "><div class="container "><div class="top-navigation-wrap"><a href="/en-US/" class="logo" aria-label="MDN homepage"><svg id="mdn-docs-logo" xmlns="http://www.w3.org/2000/svg" x="0" y="0" viewBox="0 0 694.9 104.4" style="enable-background:new 0 0 694.9 104.4" xml:space="preserve" role="img"><title>MDN Web Docs</title><path d="M40.3 0 11.7 92.1H0L28.5 0h11.8zm10.4 0v92.1H40.3V0h10.4zM91 0 62.5 92.1H50.8L79.3 0H91zm10.4 0v92.1H91V0h10.4z" class="logo-m"></path><path d="M627.9 95.6h67v8.8h-67v-8.8z" class="logo-_"></path><path d="M367 42h-4l-10.7 30.8h-5.5l-10.8-26h-.4l-10.5 26h-5.2L308.7 42h-3.8v-5.6H323V42h-6.5l6.8 20.4h.4l10.3-26h4.7l11.2 26h.5l5.7-20.3h-6.2v-5.6H367V42zm34.9 20c-.4 3.2-2 5.9-4.7 8.2-2.8 2.3-6.5 3.4-11.3 3.4-5.4 0-9.7-1.6-13.1-4.7-3.3-3.2-5-7.7-5-13.7 0-5.7 1.6-10.3 4.7-14s7.4-5.5 12.9-5.5c5.1 0 9.1 1.6 11.9 4.7s4.3 6.9 4.3 11.3c0 1.5-.2 3-.5 4.7h-25.6c.3 7.7 4 11.6 10.9 11.6 2.9 0 5.1-.7 6.5-2 1.5-1.4 2.5-3 3-4.9l6 .9zM394 51.3c.2-2.4-.4-4.7-1.8-6.9s-3.8-3.3-7-3.3c-3.1 0-5.3 1-6.9 3-1.5 2-2.5 4.4-2.8 7.2H394zm51 2.4c0 5-1.3 9.5-4 13.7s-6.9 6.2-12.7 6.2c-6 0-10.3-2.2-12.7-6.7-.1.4-.2 1.4-.4 2.9s-.3 2.5-.4 2.9h-7.3c.3-1.7.6-3.5.8-5.3.3-1.8.4-3.7.4-5.5V22.3h-6v-5.6H416v27c1.1-2.2 2.7-4.1 4.7-5.7 2-1.6 4.8-2.4 8.4-2.4 4.6 0 8.4 1.6 11.4 4.7 3 3.2 4.5 7.6 4.5 13.4zm-7.7.6c0-4.2-1-7.4-3-9.5-2-2.2-4.4-3.3-7.4-3.3-3.4 0-6 1.2-8 3.7-1.9 2.4-2.9 5-3 7.7V57c0 3 1 5.6 3 7.7s4.5 3.1 7.6 3.1c3.6 0 6.3-1.3 8.1-3.9 1.8-2.7 2.7-5.9 2.7-9.6zm69.2 18.5h-13.2v-7.2c-1.2 2.2-2.8 4.1-4.9 5.6-2.1 1.6-4.8 2.4-8.3 2.4-4.8 0-8.7-1.6-11.6-4.9-2.9-3.2-4.3-7.7-4.3-13.3 0-5 1.3-9.6 4-13.7 2.6-4.1 6.9-6.2 12.8-6.2 5.7 0 9.8 2.2 12.3 6.5V22.3h-8.6v-5.6h15.8v50.6h6v5.5zM493.2 56v-4.4c-.1-3-1.2-5.5-3.2-7.3s-4.4-2.8-7.2-2.8c-3.6 0-6.3 1.3-8.2 3.9-1.9 2.6-2.8 5.8-2.8 9.6 0 4.1 1 7.3 3 9.5s4.5 3.3 7.4 3.3c3.2 0 5.8-1.3 7.8-3.8 2.1-2.6 3.1-5.3 3.2-8zm53.1-1.4c0 5.6-1.8 10.2-5.3 13.7s-8.2 5.3-13.9 5.3-10.1-1.7-13.4-5.1c-3.3-3.4-5-7.9-5-13.5 0-5.3 1.6-9.9 4.7-13.7 3.2-3.8 7.9-5.7 14.2-5.7s11 1.9 14.1 5.7c3 3.7 4.6 8.1 4.6 13.3zm-7.7-.2c0-4-1-7.2-3-9.5s-4.8-3.5-8.2-3.5c-3.6 0-6.4 1.2-8.3 3.7s-2.9 5.6-2.9 9.5c0 3.7.9 6.8 2.8 9.4 1.9 2.6 4.6 3.9 8.3 3.9 3.6 0 6.4-1.3 8.4-3.8 1.9-2.6 2.9-5.8 2.9-9.7zm45 5.8c-.4 3.2-1.9 6.3-4.4 9.1-2.5 2.9-6.4 4.3-11.8 4.3-5.2 0-9.4-1.6-12.6-4.8-3.2-3.2-4.8-7.7-4.8-13.7 0-5.5 1.6-10.1 4.7-13.9 3.2-3.8 7.6-5.7 13.2-5.7 2.3 0 4.6.3 6.7.8 2.2.5 4.2 1.5 6.2 2.9l1.5 9.5-5.9.7-1.3-6.1c-2.1-1.2-4.5-1.8-7.2-1.8-3.5 0-6.1 1.2-7.7 3.7-1.7 2.5-2.5 5.7-2.5 9.6 0 4.1.9 7.3 2.7 9.5 1.8 2.3 4.4 3.4 7.8 3.4 5.2 0 8.2-2.9 9.2-8.8l6.2 1.3zm34.7 1.9c0 3.6-1.5 6.5-4.6 8.5s-7 3-11.7 3c-5.7 0-10.6-1.2-14.6-3.6l1.2-8.8 5.7.6-.2 4.7c1.1.5 2.3.9 3.6 1.1s2.6.3 3.9.3c2.4 0 4.5-.4 6.5-1.3 1.9-.9 2.9-2.2 2.9-4.1 0-1.8-.8-3.1-2.3-3.8s-3.5-1.3-5.8-1.7-4.6-.9-6.9-1.4c-2.3-.6-4.2-1.6-5.7-2.9-1.6-1.4-2.3-3.5-2.3-6.3 0-4.1 1.5-6.9 4.6-8.5s6.4-2.4 9.9-2.4c2.6 0 5 .3 7.2.9 2.2.6 4.3 1.4 6.1 2.4l.8 8.8-5.8.7-.8-5.7c-2.3-1-4.7-1.6-7.2-1.6-2.1 0-3.7.4-5.1 1.1-1.3.8-2 2-2 3.8 0 1.7.8 2.9 2.3 3.6 1.5.7 3.4 1.2 5.7 1.6 2.2.4 4.5.8 6.7 1.4 2.2.6 4.1 1.6 5.7 3 1.4 1.6 2.2 3.7 2.2 6.6zM197.6 73.2h-17.1v-5.5h3.8V51.9c0-3.7-.7-6.3-2.1-7.9-1.4-1.6-3.3-2.3-5.7-2.3-3.2 0-5.6 1.1-7.2 3.4s-2.4 4.6-2.5 6.9v15.6h6v5.5h-17.1v-5.5h3.8V51.9c0-3.8-.7-6.4-2.1-7.9-1.4-1.5-3.3-2.3-5.6-2.3-3.2 0-5.5 1.1-7.2 3.3-1.6 2.2-2.4 4.5-2.5 6.9v15.8h6.9v5.5h-20.2v-5.5h6V42.4h-6.1v-5.6h13.4v6.4c1.2-2.1 2.7-3.8 4.7-5.2 2-1.3 4.4-2 7.3-2s5.3.7 7.5 2.1c2.2 1.4 3.7 3.5 4.5 6.4 1.1-2.5 2.7-4.5 4.9-6.1s4.8-2.4 7.9-2.4c3.5 0 6.5 1.1 8.9 3.3s3.7 5.6 3.7 10.2v18.2h6.1v5.5zm42.5 0h-13.2V66c-1.2 2.2-2.8 4.1-4.9 5.6-2.1 1.6-4.8 2.4-8.3 2.4-4.8 0-8.7-1.6-11.6-4.9-2.9-3.2-4.3-7.7-4.3-13.3 0-5 1.3-9.6 4-13.7 2.6-4.1 6.9-6.2 12.8-6.2s9.8 2.2 12.3 6.5V22.7h-8.6v-5.6h15.8v50.6h6v5.5zm-13.3-16.8V52c-.1-3-1.2-5.5-3.2-7.3s-4.4-2.8-7.2-2.8c-3.6 0-6.3 1.3-8.2 3.9-1.9 2.6-2.8 5.8-2.8 9.6 0 4.1 1 7.3 3 9.5s4.5 3.3 7.4 3.3c3.2 0 5.8-1.3 7.8-3.8 2.1-2.6 3.1-5.3 3.2-8zm61.5 16.8H269v-5.5h6V51.9c0-3.7-.7-6.3-2.2-7.9-1.4-1.6-3.4-2.3-5.7-2.3-3.1 0-5.6 1-7.4 3s-2.8 4.4-2.9 7v15.9h6v5.5h-19.3v-5.5h6V42.4h-6.2v-5.6h13.6V43c2.6-4.6 6.8-6.9 12.7-6.9 3.6 0 6.7 1.1 9.2 3.3s3.7 5.6 3.7 10.2v18.2h6v5.4h-.2z" class="logo-text"></path></svg></a><button title="Open main menu" type="button" class="button action has-icon main-menu-toggle" aria-haspopup="menu" aria-label="Open main menu" aria-expanded="false"><span class="button-wrap"><span class="icon icon-menu "></span><span class="visually-hidden">Open main menu</span></span></button></div><div class="top-navigation-main"><nav class="main-nav" aria-label="Main menu"><ul class="main-menu nojs"><li class="top-level-entry-container active"><button type="button" id="references-button" class="top-level-entry menu-toggle" aria-controls="references-menu" aria-expanded="false">References</button><a href="/en-US/docs/Web" class="top-level-entry">References</a><ul id="references-menu" class="submenu references hidden inline-submenu-lg" aria-labelledby="references-button"><li class="apis-link-container mobile-only "><a href="/en-US/docs/Web" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">Overview / Web Technology</div><p class="submenu-item-description">Web technology reference for developers</p></div></a></li><li class="html-link-container "><a href="/en-US/docs/Web/HTML" class="submenu-item "><div class="submenu-icon html"></div><div class="submenu-content-container"><div class="submenu-item-heading">HTML</div><p class="submenu-item-description">Structure of content on the web</p></div></a></li><li class="css-link-container "><a href="/en-US/docs/Web/CSS" class="submenu-item "><div class="submenu-icon css"></div><div class="submenu-content-container"><div class="submenu-item-heading">CSS</div><p class="submenu-item-description">Code used to describe document style</p></div></a></li><li class="javascript-link-container "><a href="/en-US/docs/Web/JavaScript" class="submenu-item "><div class="submenu-icon javascript"></div><div class="submenu-content-container"><div class="submenu-item-heading">JavaScript</div><p class="submenu-item-description">General-purpose scripting language</p></div></a></li><li class="http-link-container "><a href="/en-US/docs/Web/HTTP" class="submenu-item "><div class="submenu-icon http"></div><div class="submenu-content-container"><div class="submenu-item-heading">HTTP</div><p class="submenu-item-description">Protocol for transmitting web resources</p></div></a></li><li class="apis-link-container "><a href="/en-US/docs/Web/API" class="submenu-item "><div class="submenu-icon apis"></div><div class="submenu-content-container"><div class="submenu-item-heading">Web APIs</div><p class="submenu-item-description">Interfaces for building web applications</p></div></a></li><li class="apis-link-container "><a href="/en-US/docs/Mozilla/Add-ons/WebExtensions" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">Web Extensions</div><p class="submenu-item-description">Developing extensions for web browsers</p></div></a></li><li class="apis-link-container desktop-only "><a href="/en-US/docs/Web" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">Web Technology</div><p class="submenu-item-description">Web technology reference for developers</p></div></a></li></ul></li><li class="top-level-entry-container "><button type="button" id="guides-button" class="top-level-entry menu-toggle" aria-controls="guides-menu" aria-expanded="false">Guides</button><a href="/en-US/docs/Learn" class="top-level-entry">Guides</a><ul id="guides-menu" class="submenu guides hidden inline-submenu-lg" aria-labelledby="guides-button"><li class="apis-link-container mobile-only "><a href="/en-US/docs/Learn" class="submenu-item "><div class="submenu-icon learn"></div><div class="submenu-content-container"><div class="submenu-item-heading">Overview / MDN Learning Area</div><p class="submenu-item-description">Learn web development</p></div></a></li><li class="apis-link-container desktop-only "><a href="/en-US/docs/Learn" class="submenu-item "><div class="submenu-icon learn"></div><div class="submenu-content-container"><div class="submenu-item-heading">MDN Learning Area</div><p class="submenu-item-description">Learn web development</p></div></a></li><li class="html-link-container "><a href="/en-US/docs/Learn/HTML" class="submenu-item "><div class="submenu-icon html"></div><div class="submenu-content-container"><div class="submenu-item-heading">HTML</div><p class="submenu-item-description">Learn to structure web content with HTML</p></div></a></li><li class="css-link-container "><a href="/en-US/docs/Learn/CSS" class="submenu-item "><div class="submenu-icon css"></div><div class="submenu-content-container"><div class="submenu-item-heading">CSS</div><p class="submenu-item-description">Learn to style content using CSS</p></div></a></li><li class="javascript-link-container "><a href="/en-US/docs/Learn/JavaScript" class="submenu-item "><div class="submenu-icon javascript"></div><div class="submenu-content-container"><div class="submenu-item-heading">JavaScript</div><p class="submenu-item-description">Learn to run scripts in the browser</p></div></a></li><li class=" "><a href="/en-US/docs/Web/Accessibility" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">Accessibility</div><p class="submenu-item-description">Learn to make the web accessible to all</p></div></a></li></ul></li><li class="top-level-entry-container "><button type="button" id="mdn-plus-button" class="top-level-entry menu-toggle" aria-controls="mdn-plus-menu" aria-expanded="false">Plus</button><a href="/en-US/plus" class="top-level-entry">Plus</a><ul id="mdn-plus-menu" class="submenu mdn-plus hidden inline-submenu-lg" aria-labelledby="mdn-plus-button"><li class=" "><a href="/en-US/plus" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">Overview</div><p class="submenu-item-description">A customized MDN experience</p></div></a></li><li class=" "><a href="/en-US/plus/ai-help" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">AI Help</div><p class="submenu-item-description">Get real-time assistance and support</p></div></a></li><li class=" "><a href="/en-US/plus/updates" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">Updates</div><p class="submenu-item-description">All browser compatibility updates at a glance</p></div></a></li><li class=" "><a href="/en-US/plus/docs/features/overview" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">Documentation</div><p class="submenu-item-description">Learn how to use MDN Plus</p></div></a></li><li class=" "><a href="/en-US/plus/docs/faq" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">FAQ</div><p class="submenu-item-description">Frequently asked questions about MDN Plus</p></div></a></li></ul></li><li class="top-level-entry-container "><a class="top-level-entry menu-link" href="/en-US/curriculum/">Curriculum <sup class="new">New</sup></a></li><li class="top-level-entry-container "><a class="top-level-entry menu-link" href="/en-US/blog/">Blog</a></li><li class="top-level-entry-container "><button type="button" id="tools-button" class="top-level-entry menu-toggle" aria-controls="tools-menu" aria-expanded="false">Tools</button><ul id="tools-menu" class="submenu tools hidden inline-submenu-lg" aria-labelledby="tools-button"><li class=" "><a href="/en-US/play" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">Playground</div><p class="submenu-item-description">Write, test and share your code</p></div></a></li><li class=" "><a href="/en-US/observatory" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">HTTP Observatory</div><p class="submenu-item-description">Scan a website for free</p></div></a></li><li class=" "><a href="/en-US/plus/ai-help" class="submenu-item "><div class="submenu-icon"></div><div class="submenu-content-container"><div class="submenu-item-heading">AI Help</div><p class="submenu-item-description">Get real-time assistance and support</p></div></a></li></ul></li></ul></nav><div class="header-search"><form action="/en-US/search" class="search-form search-widget" id="top-nav-search-form" role="search"><label id="top-nav-search-label" for="top-nav-search-input" class="visually-hidden">Search MDN</label><input aria-activedescendant="" aria-autocomplete="list" aria-controls="top-nav-search-menu" aria-expanded="false" aria-labelledby="top-nav-search-label" autoComplete="off" id="top-nav-search-input" role="combobox" type="search" class="search-input-field" name="q" placeholder=" " required="" value=""/><button type="button" class="button action has-icon clear-search-button"><span class="button-wrap"><span class="icon icon-cancel "></span><span class="visually-hidden">Clear search input</span></span></button><button type="submit" class="button action has-icon search-button"><span class="button-wrap"><span class="icon icon-search "></span><span class="visually-hidden">Search</span></span></button><div id="top-nav-search-menu" role="listbox" aria-labelledby="top-nav-search-label"></div></form></div><div class="theme-switcher-menu"><button type="button" class="button action has-icon theme-switcher-menu small" aria-haspopup="menu"><span class="button-wrap"><span class="icon icon-theme-os-default "></span>Theme</span></button></div><ul class="auth-container"><li><a href="/users/fxa/login/authenticate/?next=%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FConnection_management_in_HTTP_1.x" class="login-link" rel="nofollow">Log in</a></li><li><a href="/users/fxa/login/authenticate/?next=%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FConnection_management_in_HTTP_1.x" target="_self" rel="nofollow" class="button primary mdn-plus-subscribe-link"><span class="button-wrap">Sign up for free</span></a></li></ul></div></div></header><div class="article-actions-container"><div class="container"><button type="button" class="button action has-icon sidebar-button" aria-label="Expand sidebar" aria-expanded="false" aria-controls="sidebar-quicklinks"><span class="button-wrap"><span class="icon icon-sidebar "></span></span></button><nav class="breadcrumbs-container" aria-label="Breadcrumb"><ol typeof="BreadcrumbList" vocab="https://schema.org/" aria-label="breadcrumbs"><li property="itemListElement" typeof="ListItem"><a href="/en-US/docs/Web" class="breadcrumb" property="item" typeof="WebPage"><span property="name">References</span></a><meta property="position" content="1"/></li><li property="itemListElement" typeof="ListItem"><a href="/en-US/docs/Web/HTTP" class="breadcrumb" property="item" typeof="WebPage"><span property="name">HTTP</span></a><meta property="position" content="2"/></li><li property="itemListElement" typeof="ListItem"><a href="/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x" class="breadcrumb-current-page" property="item" typeof="WebPage"><span property="name">Connection management in HTTP/1.x</span></a><meta property="position" content="3"/></li></ol></nav><div class="article-actions"><button type="button" class="button action has-icon article-actions-toggle" aria-label="Article actions"><span class="button-wrap"><span class="icon icon-ellipses "></span><span class="article-actions-dialog-heading">Article Actions</span></span></button><ul class="article-actions-entries"><li class="article-actions-entry"><div class="languages-switcher-menu open-on-focus-within"><button id="languages-switcher-button" type="button" class="button action small has-icon languages-switcher-menu" aria-haspopup="menu"><span class="button-wrap"><span class="icon icon-language "></span>English (US)</span></button><div class="hidden"><ul class="submenu language-menu " aria-labelledby="language-menu-button"><li class=" "><form class="submenu-item locale-redirect-setting"><div class="group"><label class="switch"><input type="checkbox" name="locale-redirect"/><span class="slider"></span><span class="label">Remember language</span></label><a href="https://github.com/orgs/mdn/discussions/739" rel="external noopener noreferrer" target="_blank" title="Enable this setting to automatically switch to this language when it's available. (Click to learn more.)"><span class="icon icon-question-mark "></span></a></div></form></li><li class=" "><a data-locale="de" href="/de/docs/Web/HTTP/Connection_management_in_HTTP_1.x" class="button submenu-item"><span>Deutsch</span><span title="Diese Übersetzung ist Teil eines Experiments."><span class="icon icon-experimental "></span></span></a></li><li class=" "><a data-locale="es" href="/es/docs/Web/HTTP/Connection_management_in_HTTP_1.x" class="button submenu-item"><span>Español</span></a></li><li class=" "><a data-locale="ja" href="/ja/docs/Web/HTTP/Connection_management_in_HTTP_1.x" class="button submenu-item"><span>日本語</span></a></li><li class=" "><a data-locale="ko" href="/ko/docs/Web/HTTP/Connection_management_in_HTTP_1.x" class="button submenu-item"><span>한국어</span></a></li><li class=" "><a data-locale="pt-BR" href="/pt-BR/docs/Web/HTTP/Connection_management_in_HTTP_1.x" class="button submenu-item"><span>Português (do Brasil)</span></a></li><li class=" "><a data-locale="ru" href="/ru/docs/Web/HTTP/Connection_management_in_HTTP_1.x" class="button submenu-item"><span>Русский</span></a></li><li class=" "><a data-locale="zh-CN" href="/zh-CN/docs/Web/HTTP/Connection_management_in_HTTP_1.x" class="button submenu-item"><span>中文 (简体)</span></a></li></ul></div></div></li></ul></div></div></div></div><div class="main-wrapper"><div class="sidebar-container"><aside id="sidebar-quicklinks" class="sidebar" data-macro="HTTPSidebar"><button type="button" class="button action backdrop" aria-label="Collapse sidebar"><span class="button-wrap"></span></button><nav aria-label="Related Topics" class="sidebar-inner"><header class="sidebar-actions"><section class="sidebar-filter-container"><div class="sidebar-filter "><label id="sidebar-filter-label" class="sidebar-filter-label" for="sidebar-filter-input"><span class="icon icon-filter"></span><span class="visually-hidden">Filter sidebar</span></label><input id="sidebar-filter-input" autoComplete="off" class="sidebar-filter-input-field false" type="text" placeholder="Filter" value=""/><button type="button" class="button action has-icon clear-sidebar-filter-button"><span class="button-wrap"><span class="icon icon-cancel "></span><span class="visually-hidden">Clear filter input</span></span></button></div></section></header><div class="sidebar-inner-nav"><div class="in-nav-toc"><div class="document-toc-container"><section class="document-toc"><header><h2 class="document-toc-heading">In this article</h2></header><ul class="document-toc-list"><li class="document-toc-item "><a class="document-toc-link" href="#short-lived_connections">Short-lived connections</a></li><li class="document-toc-item "><a class="document-toc-link" href="#persistent_connections">Persistent connections</a></li><li class="document-toc-item "><a class="document-toc-link" href="#http_pipelining">HTTP pipelining</a></li><li class="document-toc-item "><a class="document-toc-link" href="#domain_sharding">Domain sharding</a></li><li class="document-toc-item "><a class="document-toc-link" href="#conclusion">Conclusion</a></li></ul></section></div></div><div class="sidebar-body"> <ol> <li class="section"><a href="/en-US/docs/Web/HTTP">HTTP</a></li> <li class="section no-link">Guides</li> <li><a href="/en-US/docs/Web/HTTP/Overview">An overview of HTTP</a></li> <li><a href="/en-US/docs/Web/HTTP/Session">A typical HTTP session</a></li> <li><a href="/en-US/docs/Web/HTTP/Messages">HTTP messages</a></li> <li><a href="/en-US/docs/Web/HTTP/MIME_types">MIME types (IANA media types)</a></li> <li><a href="/en-US/docs/Web/HTTP/Compression">Compression in HTTP</a></li> <li><a href="/en-US/docs/Web/HTTP/Caching">HTTP caching</a></li> <li><a href="/en-US/docs/Web/HTTP/Authentication">HTTP authentication</a></li> <li><a href="/en-US/docs/Web/HTTP/Cookies">Using HTTP cookies</a></li> <li><a href="/en-US/docs/Web/HTTP/Redirections">Redirections in HTTP</a></li> <li><a href="/en-US/docs/Web/HTTP/Conditional_requests">HTTP conditional requests</a></li> <li><a href="/en-US/docs/Web/HTTP/Range_requests">HTTP range requests</a></li> <li><a href="/en-US/docs/Web/HTTP/Content_negotiation">Content negotiation</a></li> <li><em><a href="/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x" aria-current="page">Connection management in HTTP/1.x</a></em></li> <li><a href="/en-US/docs/Web/HTTP/Evolution_of_HTTP">Evolution of HTTP</a></li> <li><a href="/en-US/docs/Web/HTTP/Protocol_upgrade_mechanism">Protocol upgrade mechanism</a></li> <li><a href="/en-US/docs/Web/HTTP/Proxy_servers_and_tunneling">Proxy servers and tunneling</a></li> <li><a href="/en-US/docs/Web/HTTP/Client_hints">HTTP Client hints</a></li> <li class="toggle"> <details> <summary>Security and privacy</summary> <ol> <li><a href="/en-US/docs/Web/Security/Practical_implementation_guides">Practical security implementation guides</a></li> <li><a href="/en-US/observatory">HTTP Observatory</a></li> <li><a href="/en-US/docs/Web/HTTP/Permissions_Policy">Permissions Policy</a></li> <li><a href="/en-US/docs/Web/HTTP/CSP">Content Security Policy (CSP)</a></li> <li><a href="/en-US/docs/Web/HTTP/CORS">Cross-Origin Resource Sharing (CORS)</a></li> <li><a href="/en-US/docs/Web/HTTP/Cross-Origin_Resource_Policy">Cross-Origin Resource Policy (CORP)</a></li> <li><a href="/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security">Strict-Transport-Security</a></li> </ol> </details> </li> <li class="section no-link">References</li> <li class="toggle"> <details> <summary>HTTP headers</summary> <ol><li><a href="/en-US/docs/Web/HTTP/Headers/Accept"><code>Accept</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Accept-CH"><code>Accept-CH</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Accept-Encoding"><code>Accept-Encoding</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Accept-Language"><code>Accept-Language</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Accept-Patch"><code>Accept-Patch</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Accept-Post"><code>Accept-Post</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Accept-Ranges"><code>Accept-Ranges</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Credentials"><code>Access-Control-Allow-Credentials</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Headers"><code>Access-Control-Allow-Headers</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Methods"><code>Access-Control-Allow-Methods</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Origin"><code>Access-Control-Allow-Origin</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Access-Control-Expose-Headers"><code>Access-Control-Expose-Headers</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Access-Control-Max-Age"><code>Access-Control-Max-Age</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Access-Control-Request-Headers"><code>Access-Control-Request-Headers</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Access-Control-Request-Method"><code>Access-Control-Request-Method</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Age"><code>Age</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Allow"><code>Allow</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Alt-Svc"><code>Alt-Svc</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Alt-Used"><code>Alt-Used</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Attribution-Reporting-Eligible"><code>Attribution-Reporting-Eligible</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Attribution-Reporting-Register-Source"><code>Attribution-Reporting-Register-Source</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Attribution-Reporting-Register-Trigger"><code>Attribution-Reporting-Register-Trigger</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Authorization"><code>Authorization</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Cache-Control"><code>Cache-Control</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Clear-Site-Data"><code>Clear-Site-Data</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Connection"><code>Connection</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Digest"><code>Content-Digest</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Disposition"><code>Content-Disposition</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-DPR"><code>Content-DPR</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Encoding"><code>Content-Encoding</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Language"><code>Content-Language</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Length"><code>Content-Length</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Location"><code>Content-Location</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Range"><code>Content-Range</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy"><code>Content-Security-Policy</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only"><code>Content-Security-Policy-Report-Only</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Type"><code>Content-Type</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Cookie"><code>Cookie</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Critical-CH"><code>Critical-CH</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy"><code>Cross-Origin-Embedder-Policy</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy"><code>Cross-Origin-Opener-Policy</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Cross-Origin-Resource-Policy"><code>Cross-Origin-Resource-Policy</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Date"><code>Date</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Device-Memory"><code>Device-Memory</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Digest"><code>Digest</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/DNT"><code>DNT</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Downlink"><code>Downlink</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/DPR"><code>DPR</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Early-Data"><code>Early-Data</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/ECT"><code>ECT</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/ETag"><code>ETag</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Expect"><code>Expect</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Expect-CT"><code>Expect-CT</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Expires"><code>Expires</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Forwarded"><code>Forwarded</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/From"><code>From</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Host"><code>Host</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/If-Match"><code>If-Match</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/If-Modified-Since"><code>If-Modified-Since</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/If-None-Match"><code>If-None-Match</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/If-Range"><code>If-Range</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/If-Unmodified-Since"><code>If-Unmodified-Since</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Keep-Alive"><code>Keep-Alive</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Last-Modified"><code>Last-Modified</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Link"><code>Link</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Location"><code>Location</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Max-Forwards"><code>Max-Forwards</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/NEL"><code>NEL</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/No-Vary-Search"><code>No-Vary-Search</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Observe-Browsing-Topics"><code>Observe-Browsing-Topics</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Origin"><code>Origin</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Origin-Agent-Cluster"><code>Origin-Agent-Cluster</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy"><code>Permissions-Policy</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Pragma"><code>Pragma</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Priority"><code>Priority</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Proxy-Authenticate"><code>Proxy-Authenticate</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Proxy-Authorization"><code>Proxy-Authorization</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Range"><code>Range</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Referer"><code>Referer</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Referrer-Policy"><code>Referrer-Policy</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Refresh"><code>Refresh</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Report-To"><code>Report-To</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Reporting-Endpoints"><code>Reporting-Endpoints</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Repr-Digest"><code>Repr-Digest</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Retry-After"><code>Retry-After</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/RTT"><code>RTT</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Save-Data"><code>Save-Data</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-Browsing-Topics"><code>Sec-Browsing-Topics</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-Prefers-Color-Scheme"><code>Sec-CH-Prefers-Color-Scheme</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-Prefers-Reduced-Motion"><code>Sec-CH-Prefers-Reduced-Motion</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-Prefers-Reduced-Transparency"><code>Sec-CH-Prefers-Reduced-Transparency</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-UA"><code>Sec-CH-UA</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Arch"><code>Sec-CH-UA-Arch</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Bitness"><code>Sec-CH-UA-Bitness</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Full-Version"><code>Sec-CH-UA-Full-Version</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Full-Version-List"><code>Sec-CH-UA-Full-Version-List</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Mobile"><code>Sec-CH-UA-Mobile</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Model"><code>Sec-CH-UA-Model</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Platform"><code>Sec-CH-UA-Platform</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Platform-Version"><code>Sec-CH-UA-Platform-Version</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-Fetch-Dest"><code>Sec-Fetch-Dest</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-Fetch-Mode"><code>Sec-Fetch-Mode</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-Fetch-Site"><code>Sec-Fetch-Site</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-Fetch-User"><code>Sec-Fetch-User</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-GPC"><code>Sec-GPC</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-Purpose"><code>Sec-Purpose</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-WebSocket-Accept"><code>Sec-WebSocket-Accept</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-WebSocket-Extensions"><code>Sec-WebSocket-Extensions</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-WebSocket-Key"><code>Sec-WebSocket-Key</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-WebSocket-Protocol"><code>Sec-WebSocket-Protocol</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Sec-WebSocket-Version"><code>Sec-WebSocket-Version</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Server"><code>Server</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Server-Timing"><code>Server-Timing</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Service-Worker-Navigation-Preload"><code>Service-Worker-Navigation-Preload</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Set-Cookie"><code>Set-Cookie</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Set-Login"><code>Set-Login</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/SourceMap"><code>SourceMap</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Speculation-Rules"><code>Speculation-Rules</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security"><code>Strict-Transport-Security</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Supports-Loading-Mode"><code>Supports-Loading-Mode</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/TE"><code>TE</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Timing-Allow-Origin"><code>Timing-Allow-Origin</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Tk"><code>Tk</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Trailer"><code>Trailer</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Transfer-Encoding"><code>Transfer-Encoding</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Upgrade"><code>Upgrade</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Upgrade-Insecure-Requests"><code>Upgrade-Insecure-Requests</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/User-Agent"><code>User-Agent</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Vary"><code>Vary</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Via"><code>Via</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Viewport-Width"><code>Viewport-Width</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Want-Content-Digest"><code>Want-Content-Digest</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Want-Digest"><code>Want-Digest</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Want-Repr-Digest"><code>Want-Repr-Digest</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Warning"><code>Warning</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Width"><code>Width</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/WWW-Authenticate"><code>WWW-Authenticate</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options"><code>X-Content-Type-Options</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/X-DNS-Prefetch-Control"><code>X-DNS-Prefetch-Control</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/X-Forwarded-For"><code>X-Forwarded-For</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/X-Forwarded-Host"><code>X-Forwarded-Host</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/X-Forwarded-Proto"><code>X-Forwarded-Proto</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/X-Frame-Options"><code>X-Frame-Options</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/X-XSS-Protection"><code>X-XSS-Protection</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li></ol> </details> </li> <li class="toggle"> <details> <summary>HTTP request methods</summary> <ol><li><a href="/en-US/docs/Web/HTTP/Methods/CONNECT"><code>CONNECT</code></a></li><li><a href="/en-US/docs/Web/HTTP/Methods/DELETE"><code>DELETE</code></a></li><li><a href="/en-US/docs/Web/HTTP/Methods/GET"><code>GET</code></a></li><li><a href="/en-US/docs/Web/HTTP/Methods/HEAD"><code>HEAD</code></a></li><li><a href="/en-US/docs/Web/HTTP/Methods/OPTIONS"><code>OPTIONS</code></a></li><li><a href="/en-US/docs/Web/HTTP/Methods/PATCH"><code>PATCH</code></a></li><li><a href="/en-US/docs/Web/HTTP/Methods/POST"><code>POST</code></a></li><li><a href="/en-US/docs/Web/HTTP/Methods/PUT"><code>PUT</code></a></li><li><a href="/en-US/docs/Web/HTTP/Methods/TRACE"><code>TRACE</code></a></li></ol> </details> </li> <li class="toggle"> <details> <summary>HTTP response status codes</summary> <ol><li><a href="/en-US/docs/Web/HTTP/Status/100"><code>100 Continue</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/101"><code>101 Switching Protocols</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/102"><code>102 Processing</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/103"><code>103 Early Hints</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/200"><code>200 OK</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/201"><code>201 Created</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/202"><code>202 Accepted</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/203"><code>203 Non-Authoritative Information</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/204"><code>204 No Content</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/205"><code>205 Reset Content</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/206"><code>206 Partial Content</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/207"><code>207 Multi-Status</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/208"><code>208 Already Reported</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/226"><code>226 IM Used</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/300"><code>300 Multiple Choices</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/301"><code>301 Moved Permanently</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/302"><code>302 Found</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/303"><code>303 See Other</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/304"><code>304 Not Modified</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/307"><code>307 Temporary Redirect</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/308"><code>308 Permanent Redirect</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/400"><code>400 Bad Request</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/401"><code>401 Unauthorized</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/402"><code>402 Payment Required</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/403"><code>403 Forbidden</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/404"><code>404 Not Found</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/405"><code>405 Method Not Allowed</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/406"><code>406 Not Acceptable</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/407"><code>407 Proxy Authentication Required</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/408"><code>408 Request Timeout</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/409"><code>409 Conflict</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/410"><code>410 Gone</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/411"><code>411 Length Required</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/412"><code>412 Precondition Failed</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/413"><code>413 Content Too Large</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/414"><code>414 URI Too Long</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/415"><code>415 Unsupported Media Type</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/416"><code>416 Range Not Satisfiable</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/417"><code>417 Expectation Failed</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/418"><code>418 I'm a teapot</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/421"><code>421 Misdirected Request</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/422"><code>422 Unprocessable Content</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/423"><code>423 Locked</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/424"><code>424 Failed Dependency</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/425"><code>425 Too Early</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/426"><code>426 Upgrade Required</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/428"><code>428 Precondition Required</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/429"><code>429 Too Many Requests</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/431"><code>431 Request Header Fields Too Large</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/451"><code>451 Unavailable For Legal Reasons</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/500"><code>500 Internal Server Error</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/501"><code>501 Not Implemented</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/502"><code>502 Bad Gateway</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/503"><code>503 Service Unavailable</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/504"><code>504 Gateway Timeout</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/505"><code>505 HTTP Version Not Supported</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/506"><code>506 Variant Also Negotiates</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/507"><code>507 Insufficient Storage</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/508"><code>508 Loop Detected</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/510"><code>510 Not Extended</code></a></li><li><a href="/en-US/docs/Web/HTTP/Status/511"><code>511 Network Authentication Required</code></a></li></ol> </details> </li> <li class="toggle"> <details> <summary>CSP directives</summary> <ol><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/base-uri"><code>CSP: base-uri</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/block-all-mixed-content"><code>CSP: block-all-mixed-content</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/child-src"><code>CSP: child-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/connect-src"><code>CSP: connect-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/default-src"><code>CSP: default-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/fenced-frame-src"><code>CSP: fenced-frame-src</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/font-src"><code>CSP: font-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/form-action"><code>CSP: form-action</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/frame-ancestors"><code>CSP: frame-ancestors</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/frame-src"><code>CSP: frame-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/img-src"><code>CSP: img-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/manifest-src"><code>CSP: manifest-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/media-src"><code>CSP: media-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/object-src"><code>CSP: object-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/prefetch-src"><code>CSP: prefetch-src</code></a><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/report-to"><code>CSP: report-to</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/report-uri"><code>CSP: report-uri</code></a><abbr class="icon icon-deprecated" title="Deprecated. Not for use in new websites."> <span class="visually-hidden">Deprecated</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/require-trusted-types-for"><code>CSP: require-trusted-types-for</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/sandbox"><code>CSP: sandbox</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src"><code>CSP: script-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src-attr"><code>CSP: script-src-attr</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src-elem"><code>CSP: script-src-elem</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/style-src"><code>CSP: style-src</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/style-src-attr"><code>CSP: style-src-attr</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/style-src-elem"><code>CSP: style-src-elem</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/trusted-types"><code>CSP: trusted-types</code></a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/upgrade-insecure-requests"><code>CSP: upgrade-insecure-requests</code></a></li><li><a href="/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/worker-src"><code>CSP: worker-src</code></a></li></ol> </details> </li> <li class="toggle"> <details> <summary>CORS errors</summary> <ol><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSDisabled">Reason: CORS disabled</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSAllowOriginNotMatchingOrigin">Reason: CORS header 'Access-Control-Allow-Origin' does not match 'xyz'</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSMissingAllowOrigin">Reason: CORS header 'Access-Control-Allow-Origin' missing</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSOriginHeaderNotAdded">Reason: CORS header 'Origin' cannot be added</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSPreflightDidNotSucceed">Reason: CORS preflight channel did not succeed</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSDidNotSucceed">Reason: CORS request did not succeed</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSExternalRedirectNotAllowed">Reason: CORS request external redirect not allowed</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSRequestNotHttp">Reason: CORS request not HTTP</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSNotSupportingCredentials">Reason: Credential is not supported if the CORS header 'Access-Control-Allow-Origin' is '*'</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSMethodNotFound">Reason: Did not find method in CORS header 'Access-Control-Allow-Methods'</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSMIssingAllowCredentials">Reason: expected 'true' in CORS header 'Access-Control-Allow-Credentials'</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSInvalidAllowHeader">Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Headers'</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSInvalidAllowMethod">Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Methods'</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSMissingAllowHeaderFromPreflight">Reason: missing token 'xyz' in CORS header 'Access-Control-Allow-Headers' from CORS preflight channel</a></li><li><a href="/en-US/docs/Web/HTTP/CORS/Errors/CORSMultipleAllowOriginNotAllowed">Reason: Multiple CORS header 'Access-Control-Allow-Origin' not allowed</a></li></ol> </details> </li> <li class="toggle"> <details> <summary>Permissions-Policy directives</summary> <ol><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/accelerometer">Permissions-Policy: accelerometer</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/ambient-light-sensor">Permissions-Policy: ambient-light-sensor</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/attribution-reporting">Permissions-Policy: attribution-reporting</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/autoplay">Permissions-Policy: autoplay</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/bluetooth">Permissions-Policy: bluetooth</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/browsing-topics">Permissions-Policy: browsing-topics</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr><abbr class="icon icon-nonstandard" title="Non-standard. Check cross-browser support before using."> <span class="visually-hidden">Non-standard</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/camera">Permissions-Policy: camera</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/compute-pressure">Permissions-Policy: compute-pressure</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/display-capture">Permissions-Policy: display-capture</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/document-domain">Permissions-Policy: document-domain</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/encrypted-media">Permissions-Policy: encrypted-media</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/fullscreen">Permissions-Policy: fullscreen</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/gamepad">Permissions-Policy: gamepad</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/geolocation">Permissions-Policy: geolocation</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/gyroscope">Permissions-Policy: gyroscope</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/hid">Permissions-Policy: hid</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/identity-credentials-get">Permissions-Policy: identity-credentials-get</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/idle-detection">Permissions-Policy: idle-detection</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/local-fonts">Permissions-Policy: local-fonts</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/magnetometer">Permissions-Policy: magnetometer</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/microphone">Permissions-Policy: microphone</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/midi">Permissions-Policy: midi</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/otp-credentials">Permissions-Policy: otp-credentials</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/payment">Permissions-Policy: payment</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/picture-in-picture">Permissions-Policy: picture-in-picture</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/publickey-credentials-create">Permissions-Policy: publickey-credentials-create</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/publickey-credentials-get">Permissions-Policy: publickey-credentials-get</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/screen-wake-lock">Permissions-Policy: screen-wake-lock</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/serial">Permissions-Policy: serial</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/speaker-selection">Permissions-Policy: speaker-selection</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/storage-access">Permissions-Policy: storage-access</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/usb">Permissions-Policy: usb</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/web-share">Permissions-Policy: web-share</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/window-management">Permissions-Policy: window-management</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li><li><a href="/en-US/docs/Web/HTTP/Headers/Permissions-Policy/xr-spatial-tracking">Permissions-Policy: xr-spatial-tracking</a><abbr class="icon icon-experimental" title="Experimental. Expect behavior to change in the future."> <span class="visually-hidden">Experimental</span> </abbr></li></ol> </details> </li> <li><a href="/en-US/docs/Web/HTTP/Resources_and_specifications">HTTP resources and specifications</a></li> </ol> </div></div><section class="place side"></section></nav></aside><div class="toc-container"><aside class="toc"><nav><div class="document-toc-container"><section class="document-toc"><header><h2 class="document-toc-heading">In this article</h2></header><ul class="document-toc-list"><li class="document-toc-item "><a class="document-toc-link" href="#short-lived_connections">Short-lived connections</a></li><li class="document-toc-item "><a class="document-toc-link" href="#persistent_connections">Persistent connections</a></li><li class="document-toc-item "><a class="document-toc-link" href="#http_pipelining">HTTP pipelining</a></li><li class="document-toc-item "><a class="document-toc-link" href="#domain_sharding">Domain sharding</a></li><li class="document-toc-item "><a class="document-toc-link" href="#conclusion">Conclusion</a></li></ul></section></div></nav></aside><section class="place side"></section></div></div><main id="content" class="main-content "><article class="main-page-content" lang="en-US"><header><h1>Connection management in HTTP/1.x</h1></header><div class="section-content"><p>Connection management is a key topic in HTTP: opening and maintaining connections largely impacts the performance of websites and Web applications. In HTTP/1.x, there are several models: <em>short-lived connections</em>, <em>persistent connections</em>, and <em>HTTP pipelining.</em></p> <p>HTTP mostly relies on TCP for its transport protocol, providing a connection between the client and the server. In its infancy, HTTP used a single model to handle such connections. These connections were short-lived: a new one created each time a request needed sending, and closed once the answer had been received.</p> <p>This simple model held an innate limitation on performance: opening each TCP connection is a resource-consuming operation. Several messages must be exchanged between the client and the server. Network latency and bandwidth affect performance when a request needs sending. Modern Web pages require many requests (a dozen or more) to serve the amount of information needed, proving this earlier model inefficient.</p> <p>Two newer models were created in HTTP/1.1. The persistent-connection model keeps connections opened between successive requests, reducing the time needed to open new connections. The HTTP pipelining model goes one step further, by sending several successive requests without even waiting for an answer, reducing much of the latency in the network.</p> <p> <img src="/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x/http1_x_connections.png" alt="Compares the performance of the three HTTP/1.x connection models: short-lived connections, persistent connections, and HTTP pipelining." width="1012" height="670" loading="lazy"> </p> <div class="notecard note"> <p><strong>Note:</strong> HTTP/2 adds additional models for connection management.</p> </div> <p>It's important to note that connection management in HTTP applies to the connection between two consecutive nodes, which is <a href="/en-US/docs/Web/HTTP/Headers#hop-by-hop_headers">hop-by-hop</a> and not <a href="/en-US/docs/Web/HTTP/Headers#end-to-end_headers">end-to-end</a>. The model used in connections between a client and its first proxy may differ from the model between a proxy and the destination server (or any intermediate proxies). The HTTP headers involved in defining the connection model, like <a href="/en-US/docs/Web/HTTP/Headers/Connection"><code>Connection</code></a> and <a href="/en-US/docs/Web/HTTP/Headers/Keep-Alive"><code>Keep-Alive</code></a>, are <a href="/en-US/docs/Web/HTTP/Headers#hop-by-hop_headers">hop-by-hop</a> headers with their values able to be changed by intermediary nodes.</p> <p>A related topic is the concept of HTTP connection upgrades, wherein an HTTP/1.1 connection is upgraded to a different protocol, such as TLS/1.0, WebSocket, or even HTTP/2 in cleartext. This <a href="/en-US/docs/Web/HTTP/Protocol_upgrade_mechanism">protocol upgrade mechanism</a> is documented in more detail elsewhere.</p></div><section aria-labelledby="short-lived_connections"><h2 id="short-lived_connections"><a href="#short-lived_connections">Short-lived connections</a></h2><div class="section-content"><p>The original model of HTTP, and the default one in HTTP/1.0, is <em>short-lived connections</em>. Each HTTP request is completed on its own connection; this means a TCP handshake happens before each HTTP request, and these are serialized.</p> <p>The TCP handshake itself is time-consuming, but a TCP connection adapts to its load, becoming more efficient with more sustained (or warm) connections. Short-lived connections do not make use of this efficiency feature of TCP, and performance degrades from optimum by persisting to transmit over a new, cold connection.</p> <p>This model is the default model used in HTTP/1.0 (if there is no <a href="/en-US/docs/Web/HTTP/Headers/Connection"><code>Connection</code></a> header, or if its value is set to <code>close</code>). In HTTP/1.1, this model is only used when the <a href="/en-US/docs/Web/HTTP/Headers/Connection"><code>Connection</code></a> header is sent with a value of <code>close</code>.</p> <div class="notecard note"> <p><strong>Note:</strong> Unless dealing with a very old system, which doesn't support a persistent connection, there is no compelling reason to use this model.</p> </div></div></section><section aria-labelledby="persistent_connections"><h2 id="persistent_connections"><a href="#persistent_connections">Persistent connections</a></h2><div class="section-content"><p>Short-lived connections have two major hitches: the time taken to establish a new connection is significant, and performance of the underlying TCP connection gets better only when this connection has been in use for some time (warm connection). To ease these problems, the concept of a <em>persistent connection</em> has been designed, even prior to HTTP/1.1. Alternatively this may be called a <em>keep-alive connection</em>.</p> <p>A persistent connection is one which remains open for a period of time, and can be reused for several requests, saving the need for a new TCP handshake, and utilizing TCP's performance enhancing capabilities. This connection will not stay open forever: idle connections are closed after some time (a server may use the <a href="/en-US/docs/Web/HTTP/Headers/Keep-Alive"><code>Keep-Alive</code></a> header to specify a minimum time the connection should be kept open).</p> <p>Persistent connections also have drawbacks; even when idling they consume server resources, and under heavy load, <a href="/en-US/docs/Glossary/DOS_attack">DoS attacks</a> can be conducted. In such cases, using non-persistent connections, which are closed as soon as they are idle, can provide better performance.</p> <p>HTTP/1.0 connections are not persistent by default. Setting <a href="/en-US/docs/Web/HTTP/Headers/Connection"><code>Connection</code></a> to anything other than <code>close</code>, usually <code>retry-after</code>, will make them persistent.</p> <p>In HTTP/1.1, persistence is the default, and the header is no longer needed (but it is often added as a defensive measure against cases requiring a fallback to HTTP/1.0).</p></div></section><section aria-labelledby="http_pipelining"><h2 id="http_pipelining"><a href="#http_pipelining">HTTP pipelining</a></h2><div class="section-content"><div class="notecard note"> <p><strong>Note:</strong> HTTP pipelining is not activated by default in modern browsers:</p> <ul> <li>Buggy <a href="https://en.wikipedia.org/wiki/Proxy_server" class="external" target="_blank">proxies</a> are still common and these lead to strange and erratic behaviors that Web developers cannot foresee and diagnose easily.</li> <li>Pipelining is complex to implement correctly: the size of the resource being transferred, the effective <a href="https://en.wikipedia.org/wiki/Round-trip_delay_time" class="external" target="_blank">RTT</a> that will be used, as well as the effective bandwidth, have a direct incidence on the improvement provided by the pipeline. Without knowing these, important messages may be delayed behind unimportant ones. The notion of important even evolves during page layout! HTTP pipelining therefore brings a marginal improvement in most cases only.</li> <li>Pipelining is subject to the <a href="https://en.wikipedia.org/wiki/Head-of-line_blocking" class="external" target="_blank">HOL</a> problem.</li> </ul> <p>For these reasons, pipelining has been superseded by a better algorithm, <em>multiplexing</em>, that is used by HTTP/2.</p> </div> <p>By default, <a href="/en-US/docs/Web/HTTP">HTTP</a> requests are issued sequentially. The next request is only issued once the response to the current request has been received. As they are affected by network latencies and bandwidth limitations, this can result in significant delay before the next request is <em>seen</em> by the server.</p> <p>Pipelining is the process to send successive requests, over the same persistent connection, without waiting for the answer. This avoids latency of the connection. Theoretically, performance could also be improved if two HTTP requests were to be packed into the same TCP message. The typical <a href="https://en.wikipedia.org/wiki/Maximum_segment_size" class="external" target="_blank">MSS</a> (Maximum Segment Size), is big enough to contain several simple requests, although the demand in size of HTTP requests continues to grow.</p> <p>Not all types of HTTP requests can be pipelined: only <a href="/en-US/docs/Glossary/Idempotent">idempotent</a> methods, that is <a href="/en-US/docs/Web/HTTP/Methods/GET"><code>GET</code></a>, <a href="/en-US/docs/Web/HTTP/Methods/HEAD"><code>HEAD</code></a>, <a href="/en-US/docs/Web/HTTP/Methods/PUT"><code>PUT</code></a> and <a href="/en-US/docs/Web/HTTP/Methods/DELETE"><code>DELETE</code></a>, can be replayed safely. Should a failure happen, the pipeline content can be repeated.</p> <p>Today, every HTTP/1.1-compliant proxy and server should support pipelining, though many have limitations in practice: a significant reason no modern browser activates this feature by default.</p></div></section><section aria-labelledby="domain_sharding"><h2 id="domain_sharding"><a href="#domain_sharding">Domain sharding</a></h2><div class="section-content"><div class="notecard note"> <p><strong>Note:</strong> Unless you have a very specific immediate need, don't use this deprecated technique; switch to HTTP/2 instead. In HTTP/2, domain sharding is no longer useful: the HTTP/2 connection is able to handle parallel unprioritized requests very well. Domain sharding is even detrimental to performance. Most HTTP/2 implementations use a technique called <a href="https://daniel.haxx.se/blog/2016/08/18/http2-connection-coalescing/" class="external" target="_blank">connection coalescing</a> to revert eventual domain sharding.</p> </div> <p>As an HTTP/1.x connection is serializing requests, even without any ordering, it can't be optimal without large enough available bandwidth. As a solution, browsers open several connections to each domain, sending parallel requests. Default was once 2 to 3 connections, but this has now increased to a more common use of 6 parallel connections. There is a risk of triggering <a href="/en-US/docs/Glossary/DOS_attack">DoS</a> protection on the server side if attempting more than this number.</p> <p>If the server wishes a faster website or application response, it is possible for the server to force the opening of more connections. For example, instead of having all resources on the same domain, say <code>www.example.com</code>, it could split over several domains, <code>www1.example.com</code>, <code>www2.example.com</code>, <code>www3.example.com</code>. Each of these domains resolves to the <em>same</em> server, and the Web browser will open 6 connections to each (in our example, boosting the connections to 18). This technique is called <em>domain sharding</em>.</p> <p> <img src="/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x/httpsharding.png" alt="Without domain sharding, a client requests six images from a domain with a maximum of two requests taking place in parallel. With domain sharding, the images are available from two domains and the client can run four requests in parallel, downloading the images in less time." width="463" height="727" loading="lazy"> </p></div></section><section aria-labelledby="conclusion"><h2 id="conclusion"><a href="#conclusion">Conclusion</a></h2><div class="section-content"><p>Improved connection management allows considerable boosting of performance in HTTP. With HTTP/1.1 or HTTP/1.0, using a persistent connection – at least until it becomes idle – leads to the best performance. However, the failure of pipelining has lead to designing superior connection management models, which have been incorporated into HTTP/2.</p></div></section></article><aside class="article-footer"><div class="article-footer-inner"><div class="svg-container"><svg xmlns="http://www.w3.org/2000/svg" width="162" height="162" viewBox="0 0 162 162" fill="none" role="none"><mask id="b" fill="#fff"><path d="M97.203 47.04c8.113-7.886 18.004-13.871 28.906-17.492a78 78 0 0 1 33.969-3.39c11.443 1.39 22.401 5.295 32.024 11.411s17.656 14.28 23.476 23.86c5.819 9.579 9.269 20.318 10.083 31.385a69.85 69.85 0 0 1-5.387 32.44c-4.358 10.272-11.115 19.443-19.747 26.801-8.632 7.359-18.908 12.709-30.034 15.637l-6.17-21.698c7.666-2.017 14.746-5.703 20.694-10.773 5.948-5.071 10.603-11.389 13.606-18.467a48.14 48.14 0 0 0 3.712-22.352c-.561-7.625-2.938-15.025-6.948-21.625s-9.544-12.226-16.175-16.44-14.181-6.904-22.065-7.863a53.75 53.75 0 0 0-23.405 2.336c-7.513 2.495-14.327 6.62-19.918 12.053z"></path></mask><path stroke="url(#a)" stroke-dasharray="6, 6" stroke-width="2" d="M97.203 47.04c8.113-7.886 18.004-13.871 28.906-17.492a78 78 0 0 1 33.969-3.39c11.443 1.39 22.401 5.295 32.024 11.411s17.656 14.28 23.476 23.86c5.819 9.579 9.269 20.318 10.083 31.385a69.85 69.85 0 0 1-5.387 32.44c-4.358 10.272-11.115 19.443-19.747 26.801-8.632 7.359-18.908 12.709-30.034 15.637l-6.17-21.698c7.666-2.017 14.746-5.703 20.694-10.773 5.948-5.071 10.603-11.389 13.606-18.467a48.14 48.14 0 0 0 3.712-22.352c-.561-7.625-2.938-15.025-6.948-21.625s-9.544-12.226-16.175-16.44-14.181-6.904-22.065-7.863a53.75 53.75 0 0 0-23.405 2.336c-7.513 2.495-14.327 6.62-19.918 12.053z" mask="url(#b)" style="stroke:url(#a)" transform="translate(-63.992 -25.587)"></path><ellipse cx="8.066" cy="111.597" fill="var(--background-tertiary)" rx="53.677" ry="53.699" transform="matrix(.71707 -.697 .7243 .6895 0 0)"></ellipse><g clip-path="url(#c)" transform="translate(-63.992 -25.587)"><path fill="#9abff5" d="m144.256 137.379 32.906 12.434a4.41 4.41 0 0 1 2.559 5.667l-9.326 24.679a4.41 4.41 0 0 1-5.667 2.559l-8.226-3.108-2.332 6.17c-.466 1.233-.375 1.883-1.609 1.417l-2.253-.527c-.411-.155-.95-.594-1.206-1.161l-4.734-10.484-12.545-4.741a4.41 4.41 0 0 1-2.559-5.667l9.325-24.679a4.41 4.41 0 0 1 5.667-2.559m9.961 29.617 8.227 3.108 3.264-8.638-.498-6.768-4.113-1.555.548 7.258-4.319-1.632zm-12.339-4.663 8.226 3.108 3.264-8.637-.498-6.769-4.113-1.554.548 7.257-4.319-1.632z"></path></g><g clip-path="url(#d)" transform="translate(-63.992 -25.587)"><path fill="#81b0f3" d="M135.35 60.136 86.67 41.654c-3.346-1.27-7.124.428-8.394 3.775L64.414 81.938c-1.27 3.347.428 7.125 3.774 8.395l12.17 4.62-3.465 9.128c-.693 1.826-1.432 2.457.394 3.15l3.014 1.625c.609.231 1.637.274 2.477-.104l15.53-6.983 18.56 7.047c3.346 1.27 7.124-.428 8.395-3.775l13.862-36.51c1.27-3.346-.428-7.124-3.775-8.395M95.261 83.207l-12.17-4.62 4.852-12.779 7.19-7.017 6.085 2.31-7.725 7.51 6.389 2.426zm18.255 6.93-12.17-4.62 4.852-12.778 7.189-7.017 6.085 2.31-7.725 7.51 6.39 2.426z"></path></g><defs><clipPath id="c"><path fill="#fff" d="m198.638 146.586-65.056-24.583-24.583 65.057 65.056 24.582z"></path></clipPath><clipPath id="d"><path fill="#fff" d="m66.438 14.055 96.242 36.54-36.54 96.243-96.243-36.54z"></path></clipPath><linearGradient id="a" x1="97.203" x2="199.995" y1="47.04" y2="152.793" gradientUnits="userSpaceOnUse"><stop stop-color="#086DFC"></stop><stop offset="0.246" stop-color="#2C81FA"></stop><stop offset="0.516" stop-color="#5497F8"></stop><stop offset="0.821" stop-color="#80B0F6"></stop><stop offset="1" stop-color="#9ABFF5"></stop></linearGradient></defs></svg></div><h2>Help improve MDN</h2><fieldset class="feedback"><label>Was this page helpful to you?</label><div class="button-container"><button type="button" class="button primary has-icon yes"><span class="button-wrap"><span class="icon icon-thumbs-up "></span>Yes</span></button><button type="button" class="button primary has-icon no"><span class="button-wrap"><span class="icon icon-thumbs-down "></span>No</span></button></div></fieldset><a class="contribute" href="https://github.com/mdn/content/blob/main/CONTRIBUTING.md" title="This will take you to our contribution guidelines on GitHub." target="_blank" rel="noopener noreferrer">Learn how to contribute</a>.<p class="last-modified-date">This page was last modified on <time dateTime="2024-07-25T21:29:40.000Z">Jul 25, 2024</time> by <a href="/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x/contributors.txt" rel="nofollow">MDN contributors</a>.</p><div id="on-github" class="on-github"><a href="https://github.com/mdn/content/blob/main/files/en-us/web/http/connection_management_in_http_1.x/index.md?plain=1" title="Folder: en-us/web/http/connection_management_in_http_1.x (Opens in a new tab)" target="_blank" rel="noopener noreferrer">View this page on GitHub</a> • <a href="https://github.com/mdn/content/issues/new?template=page-report.yml&mdn-url=https%3A%2F%2Fdeveloper.mozilla.org%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FConnection_management_in_HTTP_1.x&metadata=%3C%21--+Do+not+make+changes+below+this+line+--%3E%0A%3Cdetails%3E%0A%3Csummary%3EPage+report+details%3C%2Fsummary%3E%0A%0A*+Folder%3A+%60en-us%2Fweb%2Fhttp%2Fconnection_management_in_http_1.x%60%0A*+MDN+URL%3A+https%3A%2F%2Fdeveloper.mozilla.org%2Fen-US%2Fdocs%2FWeb%2FHTTP%2FConnection_management_in_HTTP_1.x%0A*+GitHub+URL%3A+https%3A%2F%2Fgithub.com%2Fmdn%2Fcontent%2Fblob%2Fmain%2Ffiles%2Fen-us%2Fweb%2Fhttp%2Fconnection_management_in_http_1.x%2Findex.md%0A*+Last+commit%3A+https%3A%2F%2Fgithub.com%2Fmdn%2Fcontent%2Fcommit%2Fef46a4ac6bfec3e33c9209244e7cb1a9206165d6%0A*+Document+last+modified%3A+2024-07-25T21%3A29%3A40.000Z%0A%0A%3C%2Fdetails%3E" title="This will take you to GitHub to file a new issue." target="_blank" rel="noopener noreferrer">Report a problem with this content</a></div></div></aside></main></div></div><footer id="nav-footer" class="page-footer"><div class="page-footer-grid"><div class="page-footer-logo-col"><a href="/" class="mdn-footer-logo" aria-label="MDN homepage"><svg width="48" height="17" viewBox="0 0 48 17" fill="none" xmlns="http://www.w3.org/2000/svg"><title id="mdn-footer-logo-svg">MDN logo</title><path d="M20.04 16.512H15.504V10.416C15.504 9.488 15.344 8.824 15.024 8.424C14.72 8.024 14.264 7.824 13.656 7.824C12.92 7.824 12.384 8.064 12.048 8.544C11.728 9.024 11.568 9.64 11.568 10.392V14.184H13.008V16.512H8.472V10.416C8.472 9.488 8.312 8.824 7.992 8.424C7.688 8.024 7.232 7.824 6.624 7.824C5.872 7.824 5.336 8.064 5.016 8.544C4.696 9.024 4.536 9.64 4.536 10.392V14.184H6.6V16.512H0V14.184H1.44V8.04H0.024V5.688H4.536V7.32C5.224 6.088 6.32 5.472 7.824 5.472C8.608 5.472 9.328 5.664 9.984 6.048C10.64 6.432 11.096 7.016 11.352 7.8C11.992 6.248 13.168 5.472 14.88 5.472C15.856 5.472 16.72 5.776 17.472 6.384C18.224 6.992 18.6 7.936 18.6 9.216V14.184H20.04V16.512Z" fill="currentColor"></path><path d="M33.6714 16.512H29.1354V14.496C28.8314 15.12 28.3834 15.656 27.7914 16.104C27.1994 16.536 26.4154 16.752 25.4394 16.752C24.0154 16.752 22.8954 16.264 22.0794 15.288C21.2634 14.312 20.8554 12.984 20.8554 11.304C20.8554 9.688 21.2554 8.312 22.0554 7.176C22.8554 6.04 24.0634 5.472 25.6794 5.472C26.5594 5.472 27.2794 5.648 27.8394 6C28.3994 6.352 28.8314 6.8 29.1354 7.344V2.352H26.9754V0H32.2314V14.184H33.6714V16.512ZM29.1354 11.04V10.776C29.1354 9.88 28.8954 9.184 28.4154 8.688C27.9514 8.176 27.3674 7.92 26.6634 7.92C25.9754 7.92 25.3674 8.176 24.8394 8.688C24.3274 9.2 24.0714 10.008 24.0714 11.112C24.0714 12.152 24.3114 12.944 24.7914 13.488C25.2714 14.032 25.8394 14.304 26.4954 14.304C27.3114 14.304 27.9514 13.96 28.4154 13.272C28.8954 12.584 29.1354 11.84 29.1354 11.04Z" fill="currentColor"></path><path d="M47.9589 16.512H41.9829V14.184H43.4229V10.416C43.4229 9.488 43.2629 8.824 42.9429 8.424C42.6389 8.024 42.1829 7.824 41.5749 7.824C40.8389 7.824 40.2709 8.056 39.8709 8.52C39.4709 8.968 39.2629 9.56 39.2469 10.296V14.184H40.6869V16.512H34.7109V14.184H36.1509V8.04H34.5909V5.688H39.2469V7.344C39.9669 6.096 41.1269 5.472 42.7269 5.472C43.7509 5.472 44.6389 5.776 45.3909 6.384C46.1429 6.992 46.5189 7.936 46.5189 9.216V14.184H47.9589V16.512Z" fill="currentColor"></path></svg></a><p>Your blueprint for a better internet.</p><ul class="social-icons"><li><a href="https://mozilla.social/@mdn" target="_blank" rel="me noopener noreferrer"><span class="icon icon-mastodon"></span><span class="visually-hidden">MDN on Mastodon</span></a></li><li><a href="https://twitter.com/mozdevnet" target="_blank" rel="noopener noreferrer"><span class="icon icon-twitter-x"></span><span class="visually-hidden">MDN on X (formerly Twitter)</span></a></li><li><a href="https://github.com/mdn/" target="_blank" rel="noopener noreferrer"><span class="icon icon-github-mark-small"></span><span class="visually-hidden">MDN on GitHub</span></a></li><li><a href="/en-US/blog/rss.xml" target="_blank"><span class="icon icon-feed"></span><span class="visually-hidden">MDN Blog RSS Feed</span></a></li></ul></div><div class="page-footer-nav-col-1"><h2 class="footer-nav-heading">MDN</h2><ul class="footer-nav-list"><li class="footer-nav-item"><a href="/en-US/about">About</a></li><li class="footer-nav-item"><a href="/en-US/blog/">Blog</a></li><li class="footer-nav-item"><a href="https://www.mozilla.org/en-US/careers/listings/?team=ProdOps" target="_blank" rel="noopener noreferrer">Careers</a></li><li class="footer-nav-item"><a href="/en-US/advertising">Advertise with us</a></li></ul></div><div class="page-footer-nav-col-2"><h2 class="footer-nav-heading">Support</h2><ul class="footer-nav-list"><li class="footer-nav-item"><a class="footer-nav-link" href="https://support.mozilla.org/products/mdn-plus">Product help</a></li><li class="footer-nav-item"><a class="footer-nav-link" href="/en-US/docs/MDN/Community/Issues">Report an issue</a></li></ul></div><div class="page-footer-nav-col-3"><h2 class="footer-nav-heading">Our communities</h2><ul class="footer-nav-list"><li class="footer-nav-item"><a class="footer-nav-link" href="/en-US/community">MDN Community</a></li><li class="footer-nav-item"><a class="footer-nav-link" href="https://discourse.mozilla.org/c/mdn/236" target="_blank" rel="noopener noreferrer">MDN Forum</a></li><li class="footer-nav-item"><a class="footer-nav-link" href="/discord" target="_blank" rel="noopener noreferrer">MDN Chat</a></li></ul></div><div class="page-footer-nav-col-4"><h2 class="footer-nav-heading">Developers</h2><ul class="footer-nav-list"><li class="footer-nav-item"><a class="footer-nav-link" href="/en-US/docs/Web">Web Technologies</a></li><li class="footer-nav-item"><a class="footer-nav-link" href="/en-US/docs/Learn">Learn Web Development</a></li><li class="footer-nav-item"><a class="footer-nav-link" href="/en-US/plus">MDN Plus</a></li><li class="footer-nav-item"><a href="https://hacks.mozilla.org/" target="_blank" rel="noopener noreferrer">Hacks Blog</a></li></ul></div><div class="page-footer-moz"><a href="https://www.mozilla.org/" class="footer-moz-logo-link" target="_blank" rel="noopener noreferrer"><svg width="112" height="32" fill="none" xmlns="http://www.w3.org/2000/svg"><title id="mozilla-footer-logo-svg">Mozilla logo</title><path d="M41.753 14.218c-2.048 0-3.324 1.522-3.324 4.157 0 2.423 1.119 4.286 3.29 4.286 2.082 0 3.447-1.678 3.447-4.347 0-2.826-1.522-4.096-3.413-4.096Zm54.89 7.044c0 .901.437 1.618 1.645 1.618 1.427 0 2.949-1.024 3.044-3.352-.649-.095-1.365-.185-2.02-.185-1.426-.005-2.668.397-2.668 1.92Z" fill="currentColor"></path><path d="M0 0v32h111.908V0H0Zm32.56 25.426h-5.87v-7.884c0-2.423-.806-3.352-2.39-3.352-1.924 0-2.702 1.365-2.702 3.324v4.868h1.864v3.044h-5.864v-7.884c0-2.423-.806-3.352-2.39-3.352-1.924 0-2.702 1.365-2.702 3.324v4.868h2.669v3.044H6.642v-3.044h1.863v-7.918H6.642V11.42h5.864v2.11c.839-1.489 2.3-2.39 4.252-2.39 2.02 0 3.878.963 4.566 3.01.778-1.862 2.361-3.01 4.566-3.01 2.512 0 4.812 1.522 4.812 4.84v6.402h1.863v3.044h-.005Zm9.036.307c-4.314 0-7.296-2.635-7.296-7.106 0-4.096 2.484-7.481 7.514-7.481s7.481 3.38 7.481 7.29c0 4.472-3.228 7.297-7.699 7.297Zm22.578-.307H51.942l-.403-2.11 7.7-8.846h-4.376l-.621 2.17-2.888-.313.498-4.907h12.294l.313 2.11-7.767 8.852h4.533l.654-2.172 3.167.308-.872 4.908Zm7.99 0h-4.191v-5.03h4.19v5.03Zm0-8.976h-4.191v-5.03h4.19v5.03Zm2.618 8.976 6.054-21.358h3.945l-6.054 21.358h-3.945Zm8.136 0 6.048-21.358h3.945l-6.054 21.358h-3.939Zm21.486.307c-1.863 0-2.887-1.085-3.072-2.792-.805 1.427-2.232 2.792-4.498 2.792-2.02 0-4.314-1.085-4.314-4.006 0-3.447 3.323-4.253 6.518-4.253.778 0 1.584.034 2.3.124v-.465c0-1.427-.034-3.133-2.3-3.133-.84 0-1.488.061-2.143.402l-.453 1.578-3.195-.34.549-3.224c2.45-.996 3.692-1.27 5.992-1.27 3.01 0 5.556 1.55 5.556 4.75v6.083c0 .805.314 1.085.963 1.085.184 0 .375-.034.587-.095l.034 2.11a5.432 5.432 0 0 1-2.524.654Z" fill="currentColor"></path></svg></a><ul class="footer-moz-list"><li class="footer-moz-item"><a href="https://www.mozilla.org/privacy/websites/" class="footer-moz-link" target="_blank" rel="noopener noreferrer">Website Privacy Notice</a></li><li class="footer-moz-item"><a href="https://www.mozilla.org/privacy/websites/#cookies" class="footer-moz-link" target="_blank" rel="noopener noreferrer">Cookies</a></li><li class="footer-moz-item"><a href="https://www.mozilla.org/about/legal/terms/mozilla" class="footer-moz-link" target="_blank" rel="noopener noreferrer">Legal</a></li><li class="footer-moz-item"><a href="https://www.mozilla.org/about/governance/policies/participation/" class="footer-moz-link" target="_blank" rel="noopener noreferrer">Community Participation Guidelines</a></li></ul></div><div class="page-footer-legal"><p id="license" class="page-footer-legal-text">Visit <a href="https://www.mozilla.org" target="_blank" rel="noopener noreferrer">Mozilla Corporation’s</a> not-for-profit parent, the <a target="_blank" rel="noopener noreferrer" href="https://foundation.mozilla.org/">Mozilla Foundation</a>.<br/>Portions of this content are ©1998–2024 by individual mozilla.org contributors. Content available under <a href="/en-US/docs/MDN/Writing_guidelines/Attrib_copyright_license">a Creative Commons license</a>.</p></div></div></footer></div><script type="application/json" id="hydration">{"url":"/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x","doc":{"isMarkdown":true,"isTranslated":false,"isActive":true,"flaws":{},"title":"Connection management in HTTP/1.x","mdn_url":"/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x","locale":"en-US","native":"English (US)","sidebarHTML":"\n <ol>\n <li class=\"section\"><a href=\"/en-US/docs/Web/HTTP\">HTTP</a></li>\n <li class=\"section no-link\">Guides</li>\n <li><a href=\"/en-US/docs/Web/HTTP/Overview\">An overview of HTTP</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Session\">A typical HTTP session</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Messages\">HTTP messages</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/MIME_types\">MIME types (IANA media types)</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Compression\">Compression in HTTP</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Caching\">HTTP caching</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Authentication\">HTTP authentication</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Cookies\">Using HTTP cookies</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Redirections\">Redirections in HTTP</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Conditional_requests\">HTTP conditional requests</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Range_requests\">HTTP range requests</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Content_negotiation\">Content negotiation</a></li>\n <li><em><a href=\"/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x\" aria-current=\"page\">Connection management in HTTP/1.x</a></em></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Evolution_of_HTTP\">Evolution of HTTP</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Protocol_upgrade_mechanism\">Protocol upgrade mechanism</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Proxy_servers_and_tunneling\">Proxy servers and tunneling</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Client_hints\">HTTP Client hints</a></li>\n <li class=\"toggle\">\n <details>\n <summary>Security and privacy</summary>\n <ol>\n <li><a href=\"/en-US/docs/Web/Security/Practical_implementation_guides\">Practical security implementation guides</a></li>\n <li><a href=\"/en-US/observatory\">HTTP Observatory</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Permissions_Policy\">Permissions Policy</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/CSP\">Content Security Policy (CSP)</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/CORS\">Cross-Origin Resource Sharing (CORS)</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Cross-Origin_Resource_Policy\">Cross-Origin Resource Policy (CORP)</a></li>\n <li><a href=\"/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security\">Strict-Transport-Security</a></li>\n </ol>\n </details>\n </li>\n <li class=\"section no-link\">References</li>\n <li class=\"toggle\">\n <details>\n <summary>HTTP headers</summary>\n <ol><li><a href=\"/en-US/docs/Web/HTTP/Headers/Accept\"><code>Accept</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Accept-CH\"><code>Accept-CH</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Accept-Encoding\"><code>Accept-Encoding</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Accept-Language\"><code>Accept-Language</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Accept-Patch\"><code>Accept-Patch</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Accept-Post\"><code>Accept-Post</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Accept-Ranges\"><code>Accept-Ranges</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Credentials\"><code>Access-Control-Allow-Credentials</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Headers\"><code>Access-Control-Allow-Headers</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Methods\"><code>Access-Control-Allow-Methods</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Origin\"><code>Access-Control-Allow-Origin</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Access-Control-Expose-Headers\"><code>Access-Control-Expose-Headers</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Access-Control-Max-Age\"><code>Access-Control-Max-Age</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Access-Control-Request-Headers\"><code>Access-Control-Request-Headers</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Access-Control-Request-Method\"><code>Access-Control-Request-Method</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Age\"><code>Age</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Allow\"><code>Allow</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Alt-Svc\"><code>Alt-Svc</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Alt-Used\"><code>Alt-Used</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Attribution-Reporting-Eligible\"><code>Attribution-Reporting-Eligible</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Attribution-Reporting-Register-Source\"><code>Attribution-Reporting-Register-Source</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Attribution-Reporting-Register-Trigger\"><code>Attribution-Reporting-Register-Trigger</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Authorization\"><code>Authorization</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Cache-Control\"><code>Cache-Control</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Clear-Site-Data\"><code>Clear-Site-Data</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Connection\"><code>Connection</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Digest\"><code>Content-Digest</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Disposition\"><code>Content-Disposition</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-DPR\"><code>Content-DPR</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Encoding\"><code>Content-Encoding</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Language\"><code>Content-Language</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Length\"><code>Content-Length</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Location\"><code>Content-Location</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Range\"><code>Content-Range</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy\"><code>Content-Security-Policy</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only\"><code>Content-Security-Policy-Report-Only</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Type\"><code>Content-Type</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Cookie\"><code>Cookie</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Critical-CH\"><code>Critical-CH</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy\"><code>Cross-Origin-Embedder-Policy</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy\"><code>Cross-Origin-Opener-Policy</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Cross-Origin-Resource-Policy\"><code>Cross-Origin-Resource-Policy</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Date\"><code>Date</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Device-Memory\"><code>Device-Memory</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Digest\"><code>Digest</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/DNT\"><code>DNT</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Downlink\"><code>Downlink</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/DPR\"><code>DPR</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Early-Data\"><code>Early-Data</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/ECT\"><code>ECT</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/ETag\"><code>ETag</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Expect\"><code>Expect</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Expect-CT\"><code>Expect-CT</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Expires\"><code>Expires</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Forwarded\"><code>Forwarded</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/From\"><code>From</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Host\"><code>Host</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/If-Match\"><code>If-Match</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/If-Modified-Since\"><code>If-Modified-Since</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/If-None-Match\"><code>If-None-Match</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/If-Range\"><code>If-Range</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/If-Unmodified-Since\"><code>If-Unmodified-Since</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Keep-Alive\"><code>Keep-Alive</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Last-Modified\"><code>Last-Modified</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Link\"><code>Link</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Location\"><code>Location</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Max-Forwards\"><code>Max-Forwards</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/NEL\"><code>NEL</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/No-Vary-Search\"><code>No-Vary-Search</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Observe-Browsing-Topics\"><code>Observe-Browsing-Topics</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Origin\"><code>Origin</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Origin-Agent-Cluster\"><code>Origin-Agent-Cluster</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy\"><code>Permissions-Policy</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Pragma\"><code>Pragma</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Priority\"><code>Priority</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Proxy-Authenticate\"><code>Proxy-Authenticate</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Proxy-Authorization\"><code>Proxy-Authorization</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Range\"><code>Range</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Referer\"><code>Referer</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Referrer-Policy\"><code>Referrer-Policy</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Refresh\"><code>Refresh</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Report-To\"><code>Report-To</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Reporting-Endpoints\"><code>Reporting-Endpoints</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Repr-Digest\"><code>Repr-Digest</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Retry-After\"><code>Retry-After</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/RTT\"><code>RTT</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Save-Data\"><code>Save-Data</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-Browsing-Topics\"><code>Sec-Browsing-Topics</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-Prefers-Color-Scheme\"><code>Sec-CH-Prefers-Color-Scheme</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-Prefers-Reduced-Motion\"><code>Sec-CH-Prefers-Reduced-Motion</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-Prefers-Reduced-Transparency\"><code>Sec-CH-Prefers-Reduced-Transparency</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-UA\"><code>Sec-CH-UA</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Arch\"><code>Sec-CH-UA-Arch</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Bitness\"><code>Sec-CH-UA-Bitness</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Full-Version\"><code>Sec-CH-UA-Full-Version</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Full-Version-List\"><code>Sec-CH-UA-Full-Version-List</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Mobile\"><code>Sec-CH-UA-Mobile</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Model\"><code>Sec-CH-UA-Model</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Platform\"><code>Sec-CH-UA-Platform</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-CH-UA-Platform-Version\"><code>Sec-CH-UA-Platform-Version</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-Fetch-Dest\"><code>Sec-Fetch-Dest</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-Fetch-Mode\"><code>Sec-Fetch-Mode</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-Fetch-Site\"><code>Sec-Fetch-Site</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-Fetch-User\"><code>Sec-Fetch-User</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-GPC\"><code>Sec-GPC</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-Purpose\"><code>Sec-Purpose</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-WebSocket-Accept\"><code>Sec-WebSocket-Accept</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-WebSocket-Extensions\"><code>Sec-WebSocket-Extensions</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-WebSocket-Key\"><code>Sec-WebSocket-Key</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-WebSocket-Protocol\"><code>Sec-WebSocket-Protocol</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Sec-WebSocket-Version\"><code>Sec-WebSocket-Version</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Server\"><code>Server</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Server-Timing\"><code>Server-Timing</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Service-Worker-Navigation-Preload\"><code>Service-Worker-Navigation-Preload</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Set-Cookie\"><code>Set-Cookie</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Set-Login\"><code>Set-Login</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/SourceMap\"><code>SourceMap</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Speculation-Rules\"><code>Speculation-Rules</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security\"><code>Strict-Transport-Security</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Supports-Loading-Mode\"><code>Supports-Loading-Mode</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/TE\"><code>TE</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Timing-Allow-Origin\"><code>Timing-Allow-Origin</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Tk\"><code>Tk</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Trailer\"><code>Trailer</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Transfer-Encoding\"><code>Transfer-Encoding</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Upgrade\"><code>Upgrade</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Upgrade-Insecure-Requests\"><code>Upgrade-Insecure-Requests</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/User-Agent\"><code>User-Agent</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Vary\"><code>Vary</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Via\"><code>Via</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Viewport-Width\"><code>Viewport-Width</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Want-Content-Digest\"><code>Want-Content-Digest</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Want-Digest\"><code>Want-Digest</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Want-Repr-Digest\"><code>Want-Repr-Digest</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Warning\"><code>Warning</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Width\"><code>Width</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/WWW-Authenticate\"><code>WWW-Authenticate</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options\"><code>X-Content-Type-Options</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/X-DNS-Prefetch-Control\"><code>X-DNS-Prefetch-Control</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/X-Forwarded-For\"><code>X-Forwarded-For</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/X-Forwarded-Host\"><code>X-Forwarded-Host</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/X-Forwarded-Proto\"><code>X-Forwarded-Proto</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/X-Frame-Options\"><code>X-Frame-Options</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/X-XSS-Protection\"><code>X-XSS-Protection</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr></li></ol>\n </details>\n </li>\n <li class=\"toggle\">\n <details>\n <summary>HTTP request methods</summary>\n <ol><li><a href=\"/en-US/docs/Web/HTTP/Methods/CONNECT\"><code>CONNECT</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Methods/DELETE\"><code>DELETE</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Methods/GET\"><code>GET</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Methods/HEAD\"><code>HEAD</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Methods/OPTIONS\"><code>OPTIONS</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Methods/PATCH\"><code>PATCH</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Methods/POST\"><code>POST</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Methods/PUT\"><code>PUT</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Methods/TRACE\"><code>TRACE</code></a></li></ol>\n </details>\n </li>\n <li class=\"toggle\">\n <details>\n <summary>HTTP response status codes</summary>\n <ol><li><a href=\"/en-US/docs/Web/HTTP/Status/100\"><code>100 Continue</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/101\"><code>101 Switching Protocols</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/102\"><code>102 Processing</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/103\"><code>103 Early Hints</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/200\"><code>200 OK</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/201\"><code>201 Created</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/202\"><code>202 Accepted</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/203\"><code>203 Non-Authoritative Information</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/204\"><code>204 No Content</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/205\"><code>205 Reset Content</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/206\"><code>206 Partial Content</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/207\"><code>207 Multi-Status</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/208\"><code>208 Already Reported</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/226\"><code>226 IM Used</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/300\"><code>300 Multiple Choices</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/301\"><code>301 Moved Permanently</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/302\"><code>302 Found</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/303\"><code>303 See Other</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/304\"><code>304 Not Modified</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/307\"><code>307 Temporary Redirect</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/308\"><code>308 Permanent Redirect</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/400\"><code>400 Bad Request</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/401\"><code>401 Unauthorized</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/402\"><code>402 Payment Required</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/403\"><code>403 Forbidden</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/404\"><code>404 Not Found</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/405\"><code>405 Method Not Allowed</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/406\"><code>406 Not Acceptable</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/407\"><code>407 Proxy Authentication Required</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/408\"><code>408 Request Timeout</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/409\"><code>409 Conflict</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/410\"><code>410 Gone</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/411\"><code>411 Length Required</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/412\"><code>412 Precondition Failed</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/413\"><code>413 Content Too Large</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/414\"><code>414 URI Too Long</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/415\"><code>415 Unsupported Media Type</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/416\"><code>416 Range Not Satisfiable</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/417\"><code>417 Expectation Failed</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/418\"><code>418 I'm a teapot</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/421\"><code>421 Misdirected Request</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/422\"><code>422 Unprocessable Content</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/423\"><code>423 Locked</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/424\"><code>424 Failed Dependency</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/425\"><code>425 Too Early</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/426\"><code>426 Upgrade Required</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/428\"><code>428 Precondition Required</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/429\"><code>429 Too Many Requests</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/431\"><code>431 Request Header Fields Too Large</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/451\"><code>451 Unavailable For Legal Reasons</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/500\"><code>500 Internal Server Error</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/501\"><code>501 Not Implemented</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/502\"><code>502 Bad Gateway</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/503\"><code>503 Service Unavailable</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/504\"><code>504 Gateway Timeout</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/505\"><code>505 HTTP Version Not Supported</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/506\"><code>506 Variant Also Negotiates</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/507\"><code>507 Insufficient Storage</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/508\"><code>508 Loop Detected</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/510\"><code>510 Not Extended</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Status/511\"><code>511 Network Authentication Required</code></a></li></ol>\n </details>\n </li>\n <li class=\"toggle\">\n <details>\n <summary>CSP directives</summary>\n <ol><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/base-uri\"><code>CSP: base-uri</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/block-all-mixed-content\"><code>CSP: block-all-mixed-content</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/child-src\"><code>CSP: child-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/connect-src\"><code>CSP: connect-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/default-src\"><code>CSP: default-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/fenced-frame-src\"><code>CSP: fenced-frame-src</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/font-src\"><code>CSP: font-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/form-action\"><code>CSP: form-action</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/frame-ancestors\"><code>CSP: frame-ancestors</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/frame-src\"><code>CSP: frame-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/img-src\"><code>CSP: img-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/manifest-src\"><code>CSP: manifest-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/media-src\"><code>CSP: media-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/object-src\"><code>CSP: object-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/prefetch-src\"><code>CSP: prefetch-src</code></a><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/report-to\"><code>CSP: report-to</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/report-uri\"><code>CSP: report-uri</code></a><abbr class=\"icon icon-deprecated\" title=\"Deprecated. Not for use in new websites.\">\n <span class=\"visually-hidden\">Deprecated</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/require-trusted-types-for\"><code>CSP: require-trusted-types-for</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/sandbox\"><code>CSP: sandbox</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src\"><code>CSP: script-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src-attr\"><code>CSP: script-src-attr</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src-elem\"><code>CSP: script-src-elem</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/style-src\"><code>CSP: style-src</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/style-src-attr\"><code>CSP: style-src-attr</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/style-src-elem\"><code>CSP: style-src-elem</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/trusted-types\"><code>CSP: trusted-types</code></a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/upgrade-insecure-requests\"><code>CSP: upgrade-insecure-requests</code></a></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/worker-src\"><code>CSP: worker-src</code></a></li></ol>\n </details>\n </li>\n <li class=\"toggle\">\n <details>\n <summary>CORS errors</summary>\n <ol><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSDisabled\">Reason: CORS disabled</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSAllowOriginNotMatchingOrigin\">Reason: CORS header 'Access-Control-Allow-Origin' does not match 'xyz'</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSMissingAllowOrigin\">Reason: CORS header 'Access-Control-Allow-Origin' missing</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSOriginHeaderNotAdded\">Reason: CORS header 'Origin' cannot be added</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSPreflightDidNotSucceed\">Reason: CORS preflight channel did not succeed</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSDidNotSucceed\">Reason: CORS request did not succeed</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSExternalRedirectNotAllowed\">Reason: CORS request external redirect not allowed</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSRequestNotHttp\">Reason: CORS request not HTTP</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSNotSupportingCredentials\">Reason: Credential is not supported if the CORS header 'Access-Control-Allow-Origin' is '*'</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSMethodNotFound\">Reason: Did not find method in CORS header 'Access-Control-Allow-Methods'</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSMIssingAllowCredentials\">Reason: expected 'true' in CORS header 'Access-Control-Allow-Credentials'</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSInvalidAllowHeader\">Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Headers'</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSInvalidAllowMethod\">Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Methods'</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSMissingAllowHeaderFromPreflight\">Reason: missing token 'xyz' in CORS header 'Access-Control-Allow-Headers' from CORS preflight channel</a></li><li><a href=\"/en-US/docs/Web/HTTP/CORS/Errors/CORSMultipleAllowOriginNotAllowed\">Reason: Multiple CORS header 'Access-Control-Allow-Origin' not allowed</a></li></ol>\n </details>\n </li>\n <li class=\"toggle\">\n <details>\n <summary>Permissions-Policy directives</summary>\n <ol><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/accelerometer\">Permissions-Policy: accelerometer</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/ambient-light-sensor\">Permissions-Policy: ambient-light-sensor</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/attribution-reporting\">Permissions-Policy: attribution-reporting</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/autoplay\">Permissions-Policy: autoplay</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/bluetooth\">Permissions-Policy: bluetooth</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/browsing-topics\">Permissions-Policy: browsing-topics</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr><abbr class=\"icon icon-nonstandard\" title=\"Non-standard. Check cross-browser support before using.\">\n <span class=\"visually-hidden\">Non-standard</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/camera\">Permissions-Policy: camera</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/compute-pressure\">Permissions-Policy: compute-pressure</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/display-capture\">Permissions-Policy: display-capture</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/document-domain\">Permissions-Policy: document-domain</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/encrypted-media\">Permissions-Policy: encrypted-media</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/fullscreen\">Permissions-Policy: fullscreen</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/gamepad\">Permissions-Policy: gamepad</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/geolocation\">Permissions-Policy: geolocation</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/gyroscope\">Permissions-Policy: gyroscope</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/hid\">Permissions-Policy: hid</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/identity-credentials-get\">Permissions-Policy: identity-credentials-get</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/idle-detection\">Permissions-Policy: idle-detection</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/local-fonts\">Permissions-Policy: local-fonts</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/magnetometer\">Permissions-Policy: magnetometer</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/microphone\">Permissions-Policy: microphone</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/midi\">Permissions-Policy: midi</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/otp-credentials\">Permissions-Policy: otp-credentials</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/payment\">Permissions-Policy: payment</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/picture-in-picture\">Permissions-Policy: picture-in-picture</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/publickey-credentials-create\">Permissions-Policy: publickey-credentials-create</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/publickey-credentials-get\">Permissions-Policy: publickey-credentials-get</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/screen-wake-lock\">Permissions-Policy: screen-wake-lock</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/serial\">Permissions-Policy: serial</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/speaker-selection\">Permissions-Policy: speaker-selection</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/storage-access\">Permissions-Policy: storage-access</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/usb\">Permissions-Policy: usb</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/web-share\">Permissions-Policy: web-share</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/window-management\">Permissions-Policy: window-management</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li><li><a href=\"/en-US/docs/Web/HTTP/Headers/Permissions-Policy/xr-spatial-tracking\">Permissions-Policy: xr-spatial-tracking</a><abbr class=\"icon icon-experimental\" title=\"Experimental. Expect behavior to change in the future.\">\n <span class=\"visually-hidden\">Experimental</span>\n</abbr></li></ol>\n </details>\n </li>\n <li><a href=\"/en-US/docs/Web/HTTP/Resources_and_specifications\">HTTP resources and specifications</a></li>\n </ol>\n","sidebarMacro":"HTTPSidebar","body":[{"type":"prose","value":{"id":null,"title":null,"isH3":false,"content":"<p>Connection management is a key topic in HTTP: opening and maintaining connections largely impacts the performance of websites and Web applications. In HTTP/1.x, there are several models: <em>short-lived connections</em>, <em>persistent connections</em>, and <em>HTTP pipelining.</em></p>\n<p>HTTP mostly relies on TCP for its transport protocol, providing a connection between the client and the server. In its infancy, HTTP used a single model to handle such connections. These connections were short-lived: a new one created each time a request needed sending, and closed once the answer had been received.</p>\n<p>This simple model held an innate limitation on performance: opening each TCP connection is a resource-consuming operation. Several messages must be exchanged between the client and the server. Network latency and bandwidth affect performance when a request needs sending. Modern Web pages require many requests (a dozen or more) to serve the amount of information needed, proving this earlier model inefficient.</p>\n<p>Two newer models were created in HTTP/1.1. The persistent-connection model keeps connections opened between successive requests, reducing the time needed to open new connections. The HTTP pipelining model goes one step further, by sending several successive requests without even waiting for an answer, reducing much of the latency in the network.</p>\n<p>\n <img src=\"/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x/http1_x_connections.png\" alt=\"Compares the performance of the three HTTP/1.x connection models: short-lived connections, persistent connections, and HTTP pipelining.\" width=\"1012\" height=\"670\" loading=\"lazy\">\n</p>\n<div class=\"notecard note\">\n <p><strong>Note:</strong> HTTP/2 adds additional models for connection management.</p>\n</div>\n<p>It's important to note that connection management in HTTP applies to the connection between two consecutive nodes, which is <a href=\"/en-US/docs/Web/HTTP/Headers#hop-by-hop_headers\">hop-by-hop</a> and not <a href=\"/en-US/docs/Web/HTTP/Headers#end-to-end_headers\">end-to-end</a>. The model used in connections between a client and its first proxy may differ from the model between a proxy and the destination server (or any intermediate proxies). The HTTP headers involved in defining the connection model, like <a href=\"/en-US/docs/Web/HTTP/Headers/Connection\"><code>Connection</code></a> and <a href=\"/en-US/docs/Web/HTTP/Headers/Keep-Alive\"><code>Keep-Alive</code></a>, are <a href=\"/en-US/docs/Web/HTTP/Headers#hop-by-hop_headers\">hop-by-hop</a> headers with their values able to be changed by intermediary nodes.</p>\n<p>A related topic is the concept of HTTP connection upgrades, wherein an HTTP/1.1 connection is upgraded to a different protocol, such as TLS/1.0, WebSocket, or even HTTP/2 in cleartext. This <a href=\"/en-US/docs/Web/HTTP/Protocol_upgrade_mechanism\">protocol upgrade mechanism</a> is documented in more detail elsewhere.</p>"}},{"type":"prose","value":{"id":"short-lived_connections","title":"Short-lived connections","isH3":false,"content":"<p>The original model of HTTP, and the default one in HTTP/1.0, is <em>short-lived connections</em>. Each HTTP request is completed on its own connection; this means a TCP handshake happens before each HTTP request, and these are serialized.</p>\n<p>The TCP handshake itself is time-consuming, but a TCP connection adapts to its load, becoming more efficient with more sustained (or warm) connections. Short-lived connections do not make use of this efficiency feature of TCP, and performance degrades from optimum by persisting to transmit over a new, cold connection.</p>\n<p>This model is the default model used in HTTP/1.0 (if there is no <a href=\"/en-US/docs/Web/HTTP/Headers/Connection\"><code>Connection</code></a> header, or if its value is set to <code>close</code>). In HTTP/1.1, this model is only used when the <a href=\"/en-US/docs/Web/HTTP/Headers/Connection\"><code>Connection</code></a> header is sent with a value of <code>close</code>.</p>\n<div class=\"notecard note\">\n <p><strong>Note:</strong> Unless dealing with a very old system, which doesn't support a persistent connection, there is no compelling reason to use this model.</p>\n</div>"}},{"type":"prose","value":{"id":"persistent_connections","title":"Persistent connections","isH3":false,"content":"<p>Short-lived connections have two major hitches: the time taken to establish a new connection is significant, and performance of the underlying TCP connection gets better only when this connection has been in use for some time (warm connection). To ease these problems, the concept of a <em>persistent connection</em> has been designed, even prior to HTTP/1.1. Alternatively this may be called a <em>keep-alive connection</em>.</p>\n<p>A persistent connection is one which remains open for a period of time, and can be reused for several requests, saving the need for a new TCP handshake, and utilizing TCP's performance enhancing capabilities. This connection will not stay open forever: idle connections are closed after some time (a server may use the <a href=\"/en-US/docs/Web/HTTP/Headers/Keep-Alive\"><code>Keep-Alive</code></a> header to specify a minimum time the connection should be kept open).</p>\n<p>Persistent connections also have drawbacks; even when idling they consume server resources, and under heavy load, <a href=\"/en-US/docs/Glossary/DOS_attack\">DoS attacks</a> can be conducted. In such cases, using non-persistent connections, which are closed as soon as they are idle, can provide better performance.</p>\n<p>HTTP/1.0 connections are not persistent by default. Setting <a href=\"/en-US/docs/Web/HTTP/Headers/Connection\"><code>Connection</code></a> to anything other than <code>close</code>, usually <code>retry-after</code>, will make them persistent.</p>\n<p>In HTTP/1.1, persistence is the default, and the header is no longer needed (but it is often added as a defensive measure against cases requiring a fallback to HTTP/1.0).</p>"}},{"type":"prose","value":{"id":"http_pipelining","title":"HTTP pipelining","isH3":false,"content":"<div class=\"notecard note\">\n <p><strong>Note:</strong> HTTP pipelining is not activated by default in modern browsers:</p>\n <ul>\n <li>Buggy <a href=\"https://en.wikipedia.org/wiki/Proxy_server\" class=\"external\" target=\"_blank\">proxies</a> are still common and these lead to strange and erratic behaviors that Web developers cannot foresee and diagnose easily.</li>\n <li>Pipelining is complex to implement correctly: the size of the resource being transferred, the effective <a href=\"https://en.wikipedia.org/wiki/Round-trip_delay_time\" class=\"external\" target=\"_blank\">RTT</a> that will be used, as well as the effective bandwidth, have a direct incidence on the improvement provided by the pipeline. Without knowing these, important messages may be delayed behind unimportant ones. The notion of important even evolves during page layout! HTTP pipelining therefore brings a marginal improvement in most cases only.</li>\n <li>Pipelining is subject to the <a href=\"https://en.wikipedia.org/wiki/Head-of-line_blocking\" class=\"external\" target=\"_blank\">HOL</a> problem.</li>\n </ul>\n <p>For these reasons, pipelining has been superseded by a better algorithm, <em>multiplexing</em>, that is used by HTTP/2.</p>\n</div>\n<p>By default, <a href=\"/en-US/docs/Web/HTTP\">HTTP</a> requests are issued sequentially. The next request is only issued once the response to the current request has been received. As they are affected by network latencies and bandwidth limitations, this can result in significant delay before the next request is <em>seen</em> by the server.</p>\n<p>Pipelining is the process to send successive requests, over the same persistent connection, without waiting for the answer. This avoids latency of the connection. Theoretically, performance could also be improved if two HTTP requests were to be packed into the same TCP message. The typical <a href=\"https://en.wikipedia.org/wiki/Maximum_segment_size\" class=\"external\" target=\"_blank\">MSS</a> (Maximum Segment Size), is big enough to contain several simple requests, although the demand in size of HTTP requests continues to grow.</p>\n<p>Not all types of HTTP requests can be pipelined: only <a href=\"/en-US/docs/Glossary/Idempotent\">idempotent</a> methods, that is <a href=\"/en-US/docs/Web/HTTP/Methods/GET\"><code>GET</code></a>, <a href=\"/en-US/docs/Web/HTTP/Methods/HEAD\"><code>HEAD</code></a>, <a href=\"/en-US/docs/Web/HTTP/Methods/PUT\"><code>PUT</code></a> and <a href=\"/en-US/docs/Web/HTTP/Methods/DELETE\"><code>DELETE</code></a>, can be replayed safely. Should a failure happen, the pipeline content can be repeated.</p>\n<p>Today, every HTTP/1.1-compliant proxy and server should support pipelining, though many have limitations in practice: a significant reason no modern browser activates this feature by default.</p>"}},{"type":"prose","value":{"id":"domain_sharding","title":"Domain sharding","isH3":false,"content":"<div class=\"notecard note\">\n <p><strong>Note:</strong> Unless you have a very specific immediate need, don't use this deprecated technique; switch to HTTP/2 instead. In HTTP/2, domain sharding is no longer useful: the HTTP/2 connection is able to handle parallel unprioritized requests very well. Domain sharding is even detrimental to performance. Most HTTP/2 implementations use a technique called <a href=\"https://daniel.haxx.se/blog/2016/08/18/http2-connection-coalescing/\" class=\"external\" target=\"_blank\">connection coalescing</a> to revert eventual domain sharding.</p>\n</div>\n<p>As an HTTP/1.x connection is serializing requests, even without any ordering, it can't be optimal without large enough available bandwidth. As a solution, browsers open several connections to each domain, sending parallel requests. Default was once 2 to 3 connections, but this has now increased to a more common use of 6 parallel connections. There is a risk of triggering <a href=\"/en-US/docs/Glossary/DOS_attack\">DoS</a> protection on the server side if attempting more than this number.</p>\n<p>If the server wishes a faster website or application response, it is possible for the server to force the opening of more connections. For example, instead of having all resources on the same domain, say <code>www.example.com</code>, it could split over several domains, <code>www1.example.com</code>, <code>www2.example.com</code>, <code>www3.example.com</code>. Each of these domains resolves to the <em>same</em> server, and the Web browser will open 6 connections to each (in our example, boosting the connections to 18). This technique is called <em>domain sharding</em>.</p>\n<p>\n <img src=\"/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x/httpsharding.png\" alt=\"Without domain sharding, a client requests six images from a domain with a maximum of two requests taking place in parallel. With domain sharding, the images are available from two domains and the client can run four requests in parallel, downloading the images in less time.\" width=\"463\" height=\"727\" loading=\"lazy\">\n</p>"}},{"type":"prose","value":{"id":"conclusion","title":"Conclusion","isH3":false,"content":"<p>Improved connection management allows considerable boosting of performance in HTTP. With HTTP/1.1 or HTTP/1.0, using a persistent connection – at least until it becomes idle – leads to the best performance. However, the failure of pipelining has lead to designing superior connection management models, which have been incorporated into HTTP/2.</p>"}}],"toc":[{"text":"Short-lived connections","id":"short-lived_connections"},{"text":"Persistent connections","id":"persistent_connections"},{"text":"HTTP pipelining","id":"http_pipelining"},{"text":"Domain sharding","id":"domain_sharding"},{"text":"Conclusion","id":"conclusion"}],"summary":"Connection management is a key topic in HTTP: opening and maintaining connections largely impacts the performance of websites and Web applications. In HTTP/1.x, there are several models: short-lived connections, persistent connections, and HTTP pipelining.","popularity":0.002,"modified":"2024-07-25T21:29:40.000Z","other_translations":[{"locale":"de","title":"Verbindungsmanagement in HTTP/1.x","native":"Deutsch"},{"locale":"es","title":"Gestión de la conexión en HTTP/1.x","native":"Español"},{"locale":"ja","title":"HTTP/1.x のコネクション管理","native":"日本語"},{"locale":"ko","title":"HTTP/1.x의 커넥션 관리","native":"한국어"},{"locale":"pt-BR","title":"Gerenciamento de Conexão em HTTP/1.x","native":"Português (do Brasil)"},{"locale":"ru","title":"Connection management in HTTP/1.x","native":"Русский"},{"locale":"zh-CN","title":"HTTP/1.x 的连接管理","native":"中文 (简体)"}],"pageType":"guide","source":{"folder":"en-us/web/http/connection_management_in_http_1.x","github_url":"https://github.com/mdn/content/blob/main/files/en-us/web/http/connection_management_in_http_1.x/index.md","last_commit_url":"https://github.com/mdn/content/commit/ef46a4ac6bfec3e33c9209244e7cb1a9206165d6","filename":"index.md"},"short_title":"Connection management in HTTP/1.x","parents":[{"uri":"/en-US/docs/Web","title":"References"},{"uri":"/en-US/docs/Web/HTTP","title":"HTTP"},{"uri":"/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x","title":"Connection management in HTTP/1.x"}],"pageTitle":"Connection management in HTTP/1.x - HTTP | MDN","noIndexing":false}}</script></body></html>