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<!doctype html><html lang="en"> <head> <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> <meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport"> <title>CSS Cascading and Inheritance Level 3</title> <meta content="ED" name="w3c-status"> <link href="https://www.w3.org/StyleSheets/TR/2021/W3C-ED" rel="stylesheet"> <meta content="Bikeshed version 60c422380, updated Thu Feb 20 19:11:22 2025 -0800" name="generator"> <link href="https://www.w3.org/TR/css-cascade-3/" rel="canonical"> <link href="https://drafts.csswg.org/csslogo.ico" rel="icon"> <meta content="c19338962cfd792d44f395e03b7430d80bbc881e" name="revision"> <meta content="dark light" name="color-scheme"> <link href="https://www.w3.org/StyleSheets/TR/2021/dark.css" media="(prefers-color-scheme: dark)" rel="stylesheet" type="text/css"> <style>/* Boilerplate: style-autolinks */ .css.css, .property.property, .descriptor.descriptor { color: var(--a-normal-text); font-size: inherit; font-family: inherit; } .css::before, .property::before, .descriptor::before { content: "‘"; } .css::after, .property::after, .descriptor::after { content: "’"; } .property, .descriptor { /* Don't wrap property and descriptor names */ white-space: nowrap; } .type { /* CSS value <type> */ font-style: italic; } pre .property::before, pre .property::after { content: ""; } [data-link-type="property"]::before, [data-link-type="propdesc"]::before, [data-link-type="descriptor"]::before, [data-link-type="value"]::before, [data-link-type="function"]::before, [data-link-type="at-rule"]::before, [data-link-type="selector"]::before, [data-link-type="maybe"]::before { content: "‘"; } [data-link-type="property"]::after, [data-link-type="propdesc"]::after, [data-link-type="descriptor"]::after, [data-link-type="value"]::after, [data-link-type="function"]::after, [data-link-type="at-rule"]::after, [data-link-type="selector"]::after, [data-link-type="maybe"]::after { content: "’"; } [data-link-type].production::before, [data-link-type].production::after, .prod [data-link-type]::before, .prod [data-link-type]::after { content: ""; } [data-link-type=element], [data-link-type=element-attr] { font-family: Menlo, Consolas, "DejaVu Sans Mono", monospace; font-size: .9em; } [data-link-type=element]::before { content: "<" } [data-link-type=element]::after { content: ">" } [data-link-type=biblio] { white-space: pre; } @media (prefers-color-scheme: dark) { :root { --selflink-text: black; --selflink-bg: silver; --selflink-hover-text: white; } } </style> <style>/* Boilerplate: style-caniuse-panel */ @media (max-width: 767px) { .caniuse-status { opacity: .1; transition: opacity .1s; } } :root { --caniuse-bg: #EEE; --caniuse-shadow: #999; --caniuse-nosupport-text: #ccc; --caniuse-partialsupport-text: #666; } @media (prefers-color-scheme: dark) { :root { --caniuse-bg: #222; --caniuse-shadow: #444; --caniuse-nosupport-text: #666; --caniuse-partialsupport-text: #bbb; } } .caniuse-status { background: var(--caniuse-bg, #EEE); border-radius: .25em; box-shadow: 0 0 3px var(--caniuse-shadow, #999); color: var(--text, black); font: 1em sans-serif; hyphens: none; max-width: min-content; overflow: hidden; padding: .2em; position: absolute; right: 0.3em; top: auto; width: fit-content; word-wrap: normal; z-index: 8; } .caniuse-status.unpositioned { display: none; } .caniuse-status.overlapping-main { opacity: .2; transition: opacity .1s; } .caniuse-status[open] { opacity: 1; z-index: 9; min-width: 9em; width: fit-content; } .caniuse-status:hover { outline: var(--text, black) 1px solid; opacity: 1; } .caniuse-status > summary { font-weight: normal; text-align: right; cursor: pointer; display: block; } .caniuse-status > p { font-size: 0.6em; margin: 0; padding: 0; clear: both; } .caniuse-status > p + p { padding-top: 0.5em; } .caniuse-status > .support { display: block; } .caniuse-status > .support > span { padding: 0.2em 0; display: block; display: table; } .caniuse-status > .support > span.partial { color: var(--caniuse-partialsupport-text, #666666); filter: grayscale(50%); } .caniuse-status > .support > span.no { color: var(--caniuse-nosupport-text, #CCCCCC); filter: grayscale(100%); } .caniuse-status > .support > span.no::before { opacity: 0.5; } .caniuse-status > .support > span:first-of-type { padding-top: 0.5em; } .caniuse-status > .support > span > span { padding: 0 0.5em; display: table-cell; vertical-align: top; } .caniuse-status > .support > span > span:first-child { width: 100%; } .caniuse-status > .support > span > span:last-child { width: 100%; white-space: pre; padding: 0; } .caniuse-status > .support > span::before { content: ' '; display: table-cell; height: 1.5em; background: no-repeat center center; background-size: contain; text-align: right; font-size: 0.75em; font-weight: bold; } .caniuse-status > .support > .and_chr::before { background-image: url(https://resources.whatwg.org/browser-logos/chrome.svg); } .caniuse-status > .support > .and_ff::before { background-image: url(https://resources.whatwg.org/browser-logos/firefox.png); } .caniuse-status > .support > .and_uc::before { background-image: url(https://resources.whatwg.org/browser-logos/uc.png); } /* UC Browser for Android */ .caniuse-status > .support > .android::before { background-image: url(https://resources.whatwg.org/browser-logos/android.svg); } .caniuse-status > .support > .bb::before { background-image: url(https://resources.whatwg.org/browser-logos/bb.jpg); } /* Blackberry Browser */ .caniuse-status > .support > .chrome::before { background-image: url(https://resources.whatwg.org/browser-logos/chrome.svg); } .caniuse-status > .support > .edge::before { background-image: url(https://resources.whatwg.org/browser-logos/edge.svg); } .caniuse-status > .support > .firefox::before { background-image: url(https://resources.whatwg.org/browser-logos/firefox.png); } .caniuse-status > .support > .ie::before { background-image: url(https://resources.whatwg.org/browser-logos/ie.png); } .caniuse-status > .support > .ie_mob::before { background-image: url(https://resources.whatwg.org/browser-logos/ie-mobile.svg); } .caniuse-status > .support > .ios_saf::before { background-image: url(https://resources.whatwg.org/browser-logos/safari-ios.svg); } .caniuse-status > .support > .op_mini::before { background-image: url(https://resources.whatwg.org/browser-logos/opera-mini.png); } .caniuse-status > .support > .op_mob::before { background-image: url(https://resources.whatwg.org/browser-logos/opera.svg); } .caniuse-status > .support > .opera::before { background-image: url(https://resources.whatwg.org/browser-logos/opera.svg); } .caniuse-status > .support > .safari::before { background-image: url(https://resources.whatwg.org/browser-logos/safari.png); } .caniuse-status > .support > .samsung::before { background-image: url(https://resources.whatwg.org/browser-logos/samsung.svg); } .caniuse-status > .caniuse { text-align: right; font-style: italic; } @media (max-width: 767px) { .caniuse-status.wrapped { width: 9em; height: auto; } .caniuse-status:not(.wrapped) { height: 1em; max-width: min-content; } .caniuse-status.wrapped > :not(input) { display: block; } .caniuse-status:not(.wrapped) > :not(input) { display: none; } } </style> <style>/* Boilerplate: style-colors */ /* Any --*-text not paired with a --*-bg is assumed to have a transparent bg */ :root { color-scheme: light dark; --text: black; --bg: white; --unofficial-watermark: url(https://www.w3.org/StyleSheets/TR/2016/logos/UD-watermark); --logo-bg: #1a5e9a; --logo-active-bg: #c00; --logo-text: white; --tocnav-normal-text: #707070; --tocnav-normal-bg: var(--bg); --tocnav-hover-text: var(--tocnav-normal-text); --tocnav-hover-bg: #f8f8f8; --tocnav-active-text: #c00; --tocnav-active-bg: var(--tocnav-normal-bg); --tocsidebar-text: var(--text); --tocsidebar-bg: #f7f8f9; --tocsidebar-shadow: rgba(0,0,0,.1); --tocsidebar-heading-text: hsla(203,20%,40%,.7); --toclink-text: var(--text); --toclink-underline: #3980b5; --toclink-visited-text: var(--toclink-text); --toclink-visited-underline: #054572; --heading-text: #005a9c; --hr-text: var(--text); --algo-border: #def; --del-text: red; --del-bg: transparent; --ins-text: #080; --ins-bg: transparent; --a-normal-text: #034575; --a-normal-underline: #bbb; --a-visited-text: var(--a-normal-text); --a-visited-underline: #707070; --a-hover-bg: rgba(75%, 75%, 75%, .25); --a-active-text: #c00; --a-active-underline: #c00; --blockquote-border: silver; --blockquote-bg: transparent; --blockquote-text: currentcolor; --issue-border: #e05252; --issue-bg: #fbe9e9; --issue-text: var(--text); --issueheading-text: #831616; --example-border: #e0cb52; --example-bg: #fcfaee; --example-text: var(--text); --exampleheading-text: #574b0f; --note-border: #52e052; --note-bg: #e9fbe9; --note-text: var(--text); --noteheading-text: hsl(120, 70%, 30%); --notesummary-underline: silver; --assertion-border: #aaa; --assertion-bg: #eee; --assertion-text: black; --advisement-border: orange; --advisement-bg: #fec; --advisement-text: var(--text); --advisementheading-text: #b35f00; --warning-border: red; --warning-bg: hsla(40,100%,50%,0.95); --warning-text: var(--text); --amendment-border: #330099; --amendment-bg: #F5F0FF; --amendment-text: var(--text); --amendmentheading-text: #220066; --def-border: #8ccbf2; --def-bg: #def; --def-text: var(--text); --defrow-border: #bbd7e9; --datacell-border: silver; --indexinfo-text: #707070; --indextable-hover-text: black; --indextable-hover-bg: #f7f8f9; --outdatedspec-bg: rgba(0, 0, 0, .5); --outdatedspec-text: black; --outdated-bg: maroon; --outdated-text: white; --outdated-shadow: red; --editedrec-bg: darkorange; } @media (prefers-color-scheme: dark) { :root { --text: #ddd; --bg: black; --unofficial-watermark: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='400' height='400'%3E%3Cg fill='%23100808' transform='translate(200 200) rotate(-45) translate(-200 -200)' stroke='%23100808' stroke-width='3'%3E%3Ctext x='50%25' y='220' style='font: bold 70px sans-serif; text-anchor: middle; letter-spacing: 6px;'%3EUNOFFICIAL%3C/text%3E%3Ctext x='50%25' y='305' style='font: bold 70px sans-serif; text-anchor: middle; letter-spacing: 6px;'%3EDRAFT%3C/text%3E%3C/g%3E%3C/svg%3E"); --logo-bg: #1a5e9a; --logo-active-bg: #c00; --logo-text: white; --tocnav-normal-text: #999; --tocnav-normal-bg: var(--bg); --tocnav-hover-text: var(--tocnav-normal-text); --tocnav-hover-bg: #080808; --tocnav-active-text: #f44; --tocnav-active-bg: var(--tocnav-normal-bg); --tocsidebar-text: var(--text); --tocsidebar-bg: #080808; --tocsidebar-shadow: rgba(255,255,255,.1); --tocsidebar-heading-text: hsla(203,20%,40%,.7); --toclink-text: var(--text); --toclink-underline: #6af; --toclink-visited-text: var(--toclink-text); --toclink-visited-underline: #054572; --heading-text: #8af; --hr-text: var(--text); --algo-border: #456; --del-text: #f44; --del-bg: transparent; --ins-text: #4a4; --ins-bg: transparent; --a-normal-text: #6af; --a-normal-underline: #555; --a-visited-text: var(--a-normal-text); --a-visited-underline: var(--a-normal-underline); --a-hover-bg: rgba(25%, 25%, 25%, .2); --a-active-text: #f44; --a-active-underline: var(--a-active-text); --borderedblock-bg: rgba(255, 255, 255, .05); --blockquote-border: silver; --blockquote-bg: var(--borderedblock-bg); --blockquote-text: currentcolor; --issue-border: #e05252; --issue-bg: var(--borderedblock-bg); --issue-text: var(--text); --issueheading-text: hsl(0deg, 70%, 70%); --example-border: hsl(50deg, 90%, 60%); --example-bg: var(--borderedblock-bg); --example-text: var(--text); --exampleheading-text: hsl(50deg, 70%, 70%); --note-border: hsl(120deg, 100%, 35%); --note-bg: var(--borderedblock-bg); --note-text: var(--text); --noteheading-text: hsl(120, 70%, 70%); --notesummary-underline: silver; --assertion-border: #444; --assertion-bg: var(--borderedblock-bg); --assertion-text: var(--text); --advisement-border: orange; --advisement-bg: #222218; --advisement-text: var(--text); --advisementheading-text: #f84; --warning-border: red; --warning-bg: hsla(40,100%,20%,0.95); --warning-text: var(--text); --amendment-border: #330099; --amendment-bg: #080010; --amendment-text: var(--text); --amendmentheading-text: #cc00ff; --def-border: #8ccbf2; --def-bg: #080818; --def-text: var(--text); --defrow-border: #136; --datacell-border: silver; --indexinfo-text: #aaa; --indextable-hover-text: var(--text); --indextable-hover-bg: #181818; --outdatedspec-bg: rgba(255, 255, 255, .5); --outdatedspec-text: black; --outdated-bg: maroon; --outdated-text: white; --outdated-shadow: red; --editedrec-bg: darkorange; } /* In case a transparent-bg image doesn't expect to be on a dark bg, which is quite common in practice... */ img { background: white; } } </style> <style>/* Boilerplate: style-counters */ body { counter-reset: example figure issue; } .issue { counter-increment: issue; } .issue:not(.no-marker)::before { content: "Issue " counter(issue); } .example { counter-increment: example; } .example:not(.no-marker)::before { content: "Example " counter(example); } .invalid.example:not(.no-marker)::before, .illegal.example:not(.no-marker)::before { content: "Invalid Example" counter(example); } figcaption { counter-increment: figure; } figcaption:not(.no-marker)::before { content: "Figure " counter(figure) " "; } </style> <style>/* Boilerplate: style-dfn-panel */ :root { --dfnpanel-bg: #ddd; --dfnpanel-text: var(--text); --dfnpanel-target-bg: #ffc; --dfnpanel-target-outline: orange; } @media (prefers-color-scheme: dark) { :root { --dfnpanel-bg: #222; --dfnpanel-text: var(--text); --dfnpanel-target-bg: #333; --dfnpanel-target-outline: silver; } } .dfn-panel { position: absolute; z-index: 35; width: 20em; width: 300px; height: auto; max-height: 500px; overflow: auto; padding: 0.5em 0.75em; font: small Helvetica Neue, sans-serif, Droid Sans Fallback; background: var(--dfnpanel-bg); color: var(--dfnpanel-text); border: outset 0.2em; white-space: normal; /* in case it's moved into a pre */ } .dfn-panel:not(.on) { display: none; } .dfn-panel * { margin: 0; padding: 0; text-indent: 0; } .dfn-panel > b { display: block; } .dfn-panel a { color: var(--dfnpanel-text); } .dfn-panel a:not(:hover) { text-decoration: none !important; border-bottom: none !important; } .dfn-panel a:focus { outline: 5px auto Highlight; outline: 5px auto -webkit-focus-ring-color; } .dfn-panel > b + b { margin-top: 0.25em; } .dfn-panel ul { padding: 0 0 0 1em; list-style: none; } .dfn-panel li a { max-width: calc(300px - 1.5em - 1em); overflow: hidden; text-overflow: ellipsis; } .dfn-panel.activated { display: inline-block; position: fixed; left: 8px; bottom: 2em; margin: 0 auto; max-width: calc(100vw - 1.5em - .4em - .5em); max-height: 30vh; transition: left 1s ease-out, bottom 1s ease-out; } .dfn-panel .link-item:hover { text-decoration: underline; } .dfn-panel .link-item .copy-icon { opacity: 0; } .dfn-panel .link-item:hover .copy-icon, .dfn-panel .link-item .copy-icon:focus { opacity: 1; } .dfn-panel .copy-icon { display: inline-block; margin-right: 0.5em; width: 0.85em; height: 1em; border-radius: 3px; background-color: #ccc; cursor: pointer; } .dfn-panel .copy-icon .icon { width: 100%; height: 100%; background-color: #fff; display: flex; justify-content: center; align-items: center; position: relative; } .dfn-panel .copy-icon .icon::before { content: ""; position: absolute; top: 0; left: 0; width: 100%; height: 100%; border: 1px solid black; background-color: #ccc; opacity: 0.25; transform: translate(3px, -3px); } .dfn-panel .copy-icon:active .icon::before { opacity: 1; } .dfn-paneled[role="button"] { cursor: help; } .highlighted { animation: target-fade 3s; } @keyframes target-fade { from { background-color: var(--dfnpanel-target-bg); outline: 5px solid var(--dfnpanel-target-outline); } to { color: var(--a-normal-text); background-color: transparent; outline: transparent; } } </style> <style>/* Boilerplate: style-issues */ a[href].issue-return { float: right; float: inline-end; color: var(--issueheading-text); font-weight: bold; text-decoration: none; } </style> <style>/* Boilerplate: style-md-lists */ /* This is a weird hack for me not yet following the commonmark spec regarding paragraph and lists. */ [data-md] > :first-child { margin-top: 0; } [data-md] > :last-child { margin-bottom: 0; } </style> <style>/* Boilerplate: style-mdn-anno */ :root { --mdn-bg: #EEE; --mdn-shadow: #999; --mdn-nosupport-text: #ccc; --mdn-pass: green; --mdn-fail: red; } @media (prefers-color-scheme: dark) { :root { --mdn-bg: #222; --mdn-shadow: #444; --mdn-nosupport-text: #666; --mdn-pass: #690; --mdn-fail: #d22; } } .mdn-anno { background: var(--mdn-bg, #EEE); border-radius: .25em; box-shadow: 0 0 3px var(--mdn-shadow, #999); color: var(--text, black); font: 1em sans-serif; hyphens: none; max-width: min-content; overflow: hidden; padding: 0.2em; position: absolute; right: 0.3em; top: auto; white-space: nowrap; word-wrap: normal; z-index: 8; } .mdn-anno.unpositioned { display: none; } .mdn-anno.overlapping-main { opacity: .2; transition: opacity .1s; } .mdn-anno[open] { opacity: 1; z-index: 9; min-width: 9em; } .mdn-anno:hover { opacity: 1; outline: var(--text, black) 1px solid; } .mdn-anno > summary { font-weight: normal; text-align: right; cursor: pointer; display: block; } .mdn-anno > summary > .less-than-two-engines-flag { color: var(--mdn-fail); padding-right: 2px; } .mdn-anno > summary > .all-engines-flag { color: var(--mdn-pass); padding-right: 2px; } .mdn-anno > summary > span { color: #fff; background-color: #000; font-weight: normal; font-family: zillaslab, Palatino, "Palatino Linotype", serif; padding: 2px 3px 0px 3px; line-height: 1.3em; vertical-align: top; } .mdn-anno > .feature { margin-top: 20px; } .mdn-anno > .feature:not(:first-of-type) { border-top: 1px solid #999; margin-top: 6px; padding-top: 2px; } .mdn-anno > .feature > .less-than-two-engines-text { color: var(--mdn-fail); } .mdn-anno > .feature > .all-engines-text { color: var(--mdn-pass); } .mdn-anno > .feature > p { font-size: .75em; margin-top: 6px; margin-bottom: 0; } .mdn-anno > .feature > p + p { margin-top: 3px; } .mdn-anno > .feature > .support { display: block; font-size: 0.6em; margin: 0; padding: 0; margin-top: 2px; } .mdn-anno > .feature > .support + div { padding-top: 0.5em; } .mdn-anno > .feature > .support > hr { display: block; border: none; border-top: 1px dotted #999; padding: 3px 0px 0px 0px; margin: 2px 3px 0px 3px; } .mdn-anno > .feature > .support > hr::before { content: ""; } .mdn-anno > .feature > .support > span { padding: 0.2em 0; display: block; display: table; } .mdn-anno > .feature > .support > span.no { color: var(--mdn-nosupport-text); filter: grayscale(100%); } .mdn-anno > .feature > .support > span.no::before { opacity: 0.5; } .mdn-anno > .feature > .support > span:first-of-type { padding-top: 0.5em; } .mdn-anno > .feature > .support > span > span { padding: 0 0.5em; display: table-cell; } .mdn-anno > .feature > .support > span > span:first-child { width: 100%; } .mdn-anno > .feature > .support > span > span:last-child { width: 100%; white-space: pre; padding: 0; } .mdn-anno > .feature > .support > span::before { content: ' '; display: table-cell; min-width: 1.5em; height: 1.5em; background: no-repeat center center; background-size: contain; text-align: right; font-size: 0.75em; font-weight: bold; } .mdn-anno > .feature > .support > .chrome_android::before { background-image: url(https://resources.whatwg.org/browser-logos/chrome.svg); } .mdn-anno > .feature > .support > .firefox_android::before { background-image: url(https://resources.whatwg.org/browser-logos/firefox.png); } .mdn-anno > .feature > .support > .chrome::before { background-image: url(https://resources.whatwg.org/browser-logos/chrome.svg); } .mdn-anno > .feature > .support > .edge_blink::before { background-image: url(https://resources.whatwg.org/browser-logos/edge.svg); } .mdn-anno > .feature > .support > .edge::before { background-image: url(https://resources.whatwg.org/browser-logos/edge_legacy.svg); } .mdn-anno > .feature > .support > .firefox::before { background-image: url(https://resources.whatwg.org/browser-logos/firefox.png); } .mdn-anno > .feature > .support > .ie::before { background-image: url(https://resources.whatwg.org/browser-logos/ie.png); } .mdn-anno > .feature > .support > .safari_ios::before { background-image: url(https://resources.whatwg.org/browser-logos/safari-ios.svg); } .mdn-anno > .feature > .support > .nodejs::before { background-image: url(https://nodejs.org/favicon.ico); } .mdn-anno > .feature > .support > .opera_android::before { background-image: url(https://resources.whatwg.org/browser-logos/opera.svg); } .mdn-anno > .feature > .support > .opera::before { background-image: url(https://resources.whatwg.org/browser-logos/opera.svg); } .mdn-anno > .feature > .support > .safari::before { background-image: url(https://resources.whatwg.org/browser-logos/safari.png); } .mdn-anno > .feature > .support > .samsunginternet_android::before { background-image: url(https://resources.whatwg.org/browser-logos/samsung.svg); } .mdn-anno > .feature > .support > .webview_android::before { background-image: url(https://resources.whatwg.org/browser-logos/android-webview.png); } .name-slug-mismatch { color: red; } .caniuse-status:hover { z-index: 9; } /* dt, li, .issue, .note, and .example are "position: relative", so to put annotation at right margin, must move to right of containing block */; .h-entry:not(.status-LS) dt > .mdn-anno, .h-entry:not(.status-LS) li > .mdn-anno, .h-entry:not(.status-LS) .issue > .mdn-anno, .h-entry:not(.status-LS) .note > .mdn-anno, .h-entry:not(.status-LS) .example > .mdn-anno { right: -6.7em; } .h-entry p + .mdn-anno { margin-top: 0; } h2 + .mdn-anno.after { margin: -48px 0 0 0; } h3 + .mdn-anno.after { margin: -46px 0 0 0; } h4 + .mdn-anno.after { margin: -42px 0 0 0; } h5 + .mdn-anno.after { margin: -40px 0 0 0; } h6 + .mdn-anno.after { margin: -40px 0 0 0; } </style> <style>/* Boilerplate: style-ref-hints */ :root { --ref-hint-bg: #ddd; --ref-hint-text: var(--text); } @media (prefers-color-scheme: dark) { :root { --ref-hint-bg: #222; --ref-hint-text: var(--text); } } .ref-hint { display: inline-block; position: absolute; z-index: 35; width: 20em; width: 300px; height: auto; max-height: 500px; overflow: auto; padding: 0.5em 0.5em; font: small Helvetica Neue, sans-serif, Droid Sans Fallback; background: var(--ref-hint-bg); color: var(--ref-hint-text); border: outset 0.2em; white-space: normal; /* in case it's moved into a pre */ } .ref-hint * { margin: 0; padding: 0; text-indent: 0; } .ref-hint ul { padding: 0 0 0 1em; list-style: none; } </style> <style>/* Boilerplate: style-selflinks */ :root { --selflink-text: white; 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--wpt-bg: hsl(0, 0%, 95%); --wpt-text: var(--text); --wptheading-text: hsl(0, 0%, 30%); } @media (prefers-color-scheme: dark) { :root { --wpt-border: hsl(0, 0%, 30%); --wpt-bg: var(--borderedblock-bg); --wpt-text: var(--text); --wptheading-text: hsl(0, 0%, 60%); } } .wpt-tests-block { list-style: none; border-left: .5em solid var(--wpt-border); background: var(--wpt-bg); color: var(--wpt-text); margin: 1em auto; padding: .5em; } .wpt-tests-block summary { color: var(--wptheading-text); font-weight: normal; text-transform: uppercase; } .wpt-tests-block summary::marker{ color: var(--wpt-border); } .wpt-tests-block summary:hover::marker{ color: var(--wpt-text); } /* The only content of a wpt test block in its closed state is the <summary>, which contains the word TESTS, and that is absolutely positioned. In that closed state, wpt test blocks are styled to have a top margin whose height is exactly equal to the height of the absolutely positioned <summary>, and no other background/padding/margin/border. The wpt test block elements will therefore allow the maring of the previous/next block elements to collapse through them; if this combined margin would be larger than its own top margin, it stays as is, and therefore the pre-existing vertical rhythm of the document is undisturbed. If that combined margin would be smaller, it is grown to that size. This means that the wpt test block ensures that there's always enough vertical space to insert the summary, without adding more than is needed. */ .wpt-tests-block:not([open]){ padding: 0; border: none; background: none; font-size: 0.75em; line-height: 1; position: relative; margin: 1em 0 0; } .wpt-tests-block:not([open]) summary { position: absolute; right: 0; bottom: 0; } /* It is possible that both the last child of a block element and the block element itself would be annotated with a <wpt> block each. If the block element has a padding or a border, that's fine, but otherwise the bottom margin of the block and of its last child would collapse and both <wpt> elements would overlap, being both placed there. To avoid that, add 1px of padding to the <wpt> element annotating the last child to prevent the bottom margin of the block and of its last child from collapsing (and as much negative margin, as wel only want to prevent margin collapsing, but are not trying to actually take more space). */ .wpt-tests-block:not([open]):last-child { padding-bottom: 1px; margin-bottom: -1px; } /* Exception to the previous rule: don't do that in non-last list items, because it's not necessary, and would therefore consume more space than strictly needed. Lists must have list items as children, not <wpt> elements, so a <wpt> element cannot be a sibling of a list item, and the collision that the previous rule avoids cannot happen. */ li:not(:last-child) > .wpt-tests-block:not([open]):last-child, dd:not(:last-child) > .wpt-tests-block:not([open]):last-child { padding-bottom: 0; margin-bottom: 0; } .wpt-tests-block:not([open]):not(:hover){ opacity: 0.5; } .wpt-tests-list { list-style: none; display: grid; margin: 0; padding: 0; grid-template-columns: 1fr max-content auto auto; grid-column-gap: .5em; } .wpt-tests-block hr:last-child { display: none; } .wpt-test { display: contents; } .wpt-test > a { text-decoration: underline; border: none; } .wpt-test > .wpt-name { grid-column: 1; } .wpt-test > .wpt-results { grid-column: 2; } .wpt-test > .wpt-live { grid-column: 3; } .wpt-test > .wpt-source { grid-column: 4; } .wpt-test > .wpt-results { display: flex; gap: .1em; } .wpt-test .wpt-result { display: inline-block; height: 1em; width: 1em; border-radius: 50%; position: relative; } </style> <body class="h-entry"> <div class="head"> <a class="logo" href="https://www.w3.org/"> <img alt="W3C" height="48" src="https://www.w3.org/StyleSheets/TR/2021/logos/W3C" width="72"> </a> <h1 class="p-name no-ref" id="title">CSS Cascading and Inheritance Level 3</h1> <a href="https://www.w3.org/standards/types/#ED">Editor’s Draft</a>, <time class="dt-updated" datetime="2024-01-30">30 January 2024</time> <details open> <summary>More details about this document</summary> <div data-fill-with="spec-metadata"> <dl> <dt>This version: <dd><a class="u-url" href="https://drafts.csswg.org/css-cascade-3/">https://drafts.csswg.org/css-cascade-3/</a> <dt>Latest published version: <dd><a href="https://www.w3.org/TR/css-cascade-3/">https://www.w3.org/TR/css-cascade-3/</a> <dt>Previous Versions: <dd><a href="https://www.w3.org/TR/2020/CR-css-cascade-3-20200817/" rel="prev">https://www.w3.org/TR/2020/CR-css-cascade-3-20200817/</a> <dd><a href="https://www.w3.org/TR/2018/CR-css-cascade-3-20180828/" rel="prev">https://www.w3.org/TR/2018/CR-css-cascade-3-20180828/</a> <dd><a href="https://www.w3.org/TR/2016/CR-css-cascade-3-20160519/" rel="prev">https://www.w3.org/TR/2016/CR-css-cascade-3-20160519/</a> <dd><a href="https://www.w3.org/TR/2015/CR-css-cascade-3-20150416/" rel="prev">https://www.w3.org/TR/2015/CR-css-cascade-3-20150416/</a> <dd><a href="https://www.w3.org/TR/2013/WD-css-cascade-3-20130730/" rel="prev">https://www.w3.org/TR/2013/WD-css-cascade-3-20130730/</a> <dd><a href="https://www.w3.org/TR/2013/WD-css3-cascade-20130103/" rel="prev">https://www.w3.org/TR/2013/WD-css3-cascade-20130103/</a> <dd><a href="https://www.w3.org/TR/2005/WD-css3-cascade-20051215/" rel="prev">https://www.w3.org/TR/2005/WD-css3-cascade-20051215/</a> <dt>Implementation Report: <dd><a href="https://drafts.csswg.org/css-cascade-3/implementation-report">https://drafts.csswg.org/css-cascade-3/implementation-report</a> <dt>Feedback: <dd><a href="https://github.com/w3c/csswg-drafts/labels/css-cascade-3">CSSWG Issues Repository</a> <dd><a href="https://drafts.csswg.org/css-cascade/issues">Disposition of Comments</a> <dt class="editor">Editors: <dd class="editor p-author h-card vcard" data-editor-id="35400"><a class="p-name fn u-url url" href="http://fantasai.inkedblade.net/contact">Elika J. Etemad / fantasai</a> (Apple) <dd class="editor p-author h-card vcard" data-editor-id="42199"><a class="p-name fn u-url url" href="http://xanthir.com/contact/">Tab Atkins Jr.</a> (Google) <dt>Suggest an Edit for this Spec: <dd><a href="https://github.com/w3c/csswg-drafts/blob/main/css-cascade-3/Overview.bs">GitHub Editor</a> </dl> </div> </details> <div data-fill-with="warning"></div> <a href="https://www.w3.org/policies/#copyright">Copyright</a> © 2024 <a href="https://www.w3.org/">World Wide Web Consortium</a>. <abbr title="World Wide Web Consortium">W3C</abbr>® <a href="https://www.w3.org/policies/#Legal_Disclaimer">liability</a>, <a href="https://www.w3.org/policies/#W3C_Trademarks">trademark</a> and <a href="https://www.w3.org/copyright/software-license/" rel="license" title="W3C Software and Document License">permissive document license</a> rules apply. <hr title="Separator for header"> </div> <div class="p-summary" data-fill-with="abstract"> <h2 class="no-num no-toc no-ref heading settled" id="abstract">Abstract</h2> This CSS module describes how to collate style rules and assign values to all properties on all elements. By way of cascading and inheritance, values are propagated for all properties on all elements. <a href="https://www.w3.org/TR/CSS/">CSS</a> is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, etc. <script> const githubPrefix = "https://w3c.github.io/csswg-drafts/"; if(location.href.slice(0, githubPrefix.length) == githubPrefix) { const suffix = location.href.slice(githubPrefix.length); const draftUrl = "https://drafts.csswg.org/" + suffix; window.location.replace(draftUrl); } </script> </div> <h2 class="no-num no-toc no-ref heading settled" id="sotd">Status of this document</h2> <div data-fill-with="status"> This is a public copy of the editors’ draft. It is provided for discussion only and may change at any moment. Its publication here does not imply endorsement of its contents by W3C. Don’t cite this document other than as work in progress. Please send feedback by <a href="https://github.com/w3c/csswg-drafts/issues">filing issues in GitHub</a> (preferred), including the spec code “css-cascade” in the title, like this: “[css-cascade] …summary of comment…”. All issues and comments are <a href="https://lists.w3.org/Archives/Public/public-css-archive/">archived</a>. Alternately, feedback can be sent to the (<a href="https://lists.w3.org/Archives/Public/www-style/">archived</a>) public mailing list <a href="mailto:www-style@w3.org?Subject=%5Bcss-cascade%5D%20PUT%20SUBJECT%20HERE">www-style@w3.org</a>. This document is governed by the <a href="https://www.w3.org/policies/process/20231103/" id="w3c_process_revision">03 November 2023 W3C Process Document</a>. </div> <div data-fill-with="at-risk"></div> <nav data-fill-with="table-of-contents" id="toc"> <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2> <ol class="toc" role="directory"> <li> <a href="#intro">1 Introduction</a> <ol class="toc"> <li><a href="#placement">1.1 Module Interactions</a> </ol> <li> <a href="#at-import">2 Importing Style Sheets: the @import rule</a> <ol class="toc"> <li><a href="#conditional-import">2.1 Conditional @import Rules</a> <li><a href="#import-processing">2.2 Processing Stylesheet Imports</a> <li><a href="#content-type">2.3 Content-Type of CSS Style Sheets</a> </ol> <li> <a href="#shorthand">3 Shorthand Properties</a> <ol class="toc"> <li><a href="#all-shorthand">3.1 Resetting All Properties: the all property</a> </ol> <li> <a href="#value-stages">4 Value Processing</a> <ol class="toc"> <li><a href="#declared">4.1 Declared Values</a> <li><a href="#cascaded">4.2 Cascaded Values</a> <li><a href="#specified">4.3 Specified Values</a> <li><a href="#computed">4.4 Computed Values</a> <li><a href="#used">4.5 Used Values</a> <li><a href="#actual">4.6 Actual Values</a> <li><a href="#stages-examples">4.7 Examples</a> </ol> <li><a href="#filtering">5 Filtering</a> <li> <a href="#cascading">6 Cascading</a> <ol class="toc"> <li><a href="#cascade-sort">6.1 Cascade Sorting Order</a> <li><a href="#cascading-origins">6.2 Cascading Origins</a> <li><a href="#importance">6.3 Important Declarations: the !important annotation</a> <li><a href="#preshint">6.4 Precedence of Non-CSS Presentational Hints</a> </ol> <li> <a href="#defaulting">7 Defaulting</a> <ol class="toc"> <li><a href="#initial-values">7.1 Initial Values</a> <li><a href="#inheriting">7.2 Inheritance</a> <li> <a href="#defaulting-keywords">7.3 Explicit Defaulting</a> <ol class="toc"> <li><a href="#initial">7.3.1 Resetting a Property: the initial keyword</a> <li><a href="#inherit">7.3.2 Explicit Inheritance: the inherit keyword</a> <li><a href="#inherit-initial">7.3.3 Erasing All Declarations: the unset keyword</a> </ol> </ol> <li> <a href="#changes">8 Changes</a> <ol class="toc"> <li><a href="#changes-2018">8.1 Changes Since the 11 February 2021 Recommendation</a> <li><a href="#changes-2">8.2 Additions Since Level 2</a> </ol> <li><a href="#acknowledgments"> Acknowledgments</a> <li><a href="#priv-sec"> Privacy and Security Considerations</a> <li> <a href="#w3c-conformance"> Conformance</a> <ol class="toc"> <li><a href="#w3c-conventions"> Document conventions</a> <li><a href="#w3c-conformance-classes"> Conformance classes</a> <li> <a href="#w3c-partial"> Partial implementations</a> <ol class="toc"> <li><a href="#w3c-conform-future-proofing"> Implementations of Unstable and Proprietary Features</a> </ol> <li><a href="#w3c-testing"> Non-experimental implementations</a> </ol> <li> <a href="#index"> Index</a> <ol class="toc"> <li><a href="#index-defined-here"> Terms defined by this specification</a> <li><a href="#index-defined-elsewhere"> Terms defined by reference</a> </ol> <li> <a href="#references"> References</a> <ol class="toc"> <li><a href="#normative"> Normative References</a> <li><a href="#informative"> Informative References</a> </ol> <li><a href="#property-index"> Property Index</a> </ol> </nav> <main> <h2 class="heading settled" data-level="1" id="intro">1. Introduction<a class="self-link" href="#intro"></a></h2> CSS defines a finite set of parameters, called <dfn class="dfn-paneled" data-dfn-for="CSS" data-dfn-type="dfn" data-export data-lt="property" id="css-property">properties</dfn>, that direct the rendering of a document. Each <a data-link-type="dfn">property</a> has a name (e.g., <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-color-4/#propdef-color" id="ref-for-propdef-color">color</a>, font-size, or <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-backgrounds-3/#propdef-border-style" id="ref-for-propdef-border-style">border-style</a>), a value space (e.g., <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-color-5/#typedef-color" id="ref-for-typedef-color"><color></a>, <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#typedef-length-percentage" id="ref-for-typedef-length-percentage"><length-percentage></a>, [ solid | dashed | dotted | … ]), and a defined behavior on the rendering of the document. Properties values are assigned to various parts of the document via <a data-link-type="dfn" href="https://drafts.csswg.org/css-syntax-3/#css-property-declarations" id="ref-for-css-property-declarations">property declarations</a>, which assign the property a value (e.g. <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css2/#valdef-color-red" id="ref-for-valdef-color-red">red</a>, 12pt, <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-backgrounds-3/#valdef-line-style-dotted" id="ref-for-valdef-line-style-dotted">dotted</a>) for the associated element or box. One of the fundamental design principles of CSS is <a data-link-type="dfn" href="#cascade" id="ref-for-cascade">cascading</a>, which allows several style sheets to influence the presentation of a document. When different declarations try to set a value for the same element/property combination, the conflicts must somehow be resolved. The opposite problem arises when no declarations try to set a the value for an element/property combination. In this case, a value is be found by way of <a data-link-type="dfn" href="#css-inheritance" id="ref-for-css-inheritance">inheritance</a> or by looking at the property’s <a data-link-type="dfn" href="#initial-value" id="ref-for-initial-value">initial value</a>. The <a href="#cascade" id="ref-for-cascade①⓪">cascading</a> and <a href="#defaulting">defaulting</a> process takes a set of declarations as input, and outputs a <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value">specified value</a> for each property on each element. The rules for finding the specified value for all properties on all elements in the document are described in this specification. The rules for finding the specified values in the page context and its margin boxes are described in <a data-link-type="biblio" href="#biblio-css-page-3" title="CSS Paged Media Module Level 3">[css-page-3]</a>. <h3 class="heading settled" data-level="1.1" id="placement">1.1. Module Interactions<a class="self-link" href="#placement"></a></h3> This section is normative. This module replaces and extends the rules for assigning property values, cascading, and inheritance defined in <a data-link-type="biblio" href="#biblio-css2" title="Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification">[CSS2]</a> chapter 6. Other CSS modules may expand the definitions of some of the syntax and features defined here. For example, the Media Queries Level 4 specification, when combined with this module, expands the definition of the <a class="production css" data-link-type="type" href="https://drafts.csswg.org/mediaqueries-4/#typedef-media-query" id="ref-for-typedef-media-query"><media-query></a> value type as used in this specification. <h2 class="heading settled" data-level="2" id="at-import">2. Importing Style Sheets: the <a class="css" data-link-type="maybe" href="#at-ruledef-import" id="ref-for-at-ruledef-import">@import</a> rule<a class="self-link" href="#at-import"></a></h2> The <dfn class="dfn-paneled css" data-dfn-type="at-rule" data-export id="at-ruledef-import">@import</dfn> rule allows users to import style rules from other style sheets. If an <a class="css" data-link-type="maybe" href="#at-ruledef-import" id="ref-for-at-ruledef-import①">@import</a> rule refers to a valid stylesheet, user agents must treat the contents of the stylesheet as if they were written in place of the @import rule, with two exceptions: <ul> <li data-md> If a feature (such as the <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-namespaces-3/#at-ruledef-namespace" id="ref-for-at-ruledef-namespace">@namespace</a> rule) explicitly defines that it only applies to a particular stylesheet, and not any imported ones, then it doesn’t apply to the imported stylesheet. <li data-md> If a feature relies on the relative ordering of two or more constructs in a stylesheet (such as the requirement that <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-namespaces-3/#at-ruledef-namespace" id="ref-for-at-ruledef-namespace①">@namespace</a> rules must not have any other rules other than <a class="css" data-link-type="maybe" href="#at-ruledef-import" id="ref-for-at-ruledef-import③">@import</a> preceding it), it only applies between constructs in the same stylesheet. </ul> <a class="self-link" href="#example-d425da12"></a> For example, <a data-link-type="dfn" href="https://drafts.csswg.org/cssom-1/#cssstyledeclaration-declarations" id="ref-for-cssstyledeclaration-declarations">declarations</a> in style rules from imported stylesheets interact with the cascade as if they were written literally into the stylesheet at the point of the <a class="css" data-link-type="maybe" href="#at-ruledef-import" id="ref-for-at-ruledef-import④">@import</a>. Any <a class="css" data-link-type="maybe" href="#at-ruledef-import" id="ref-for-at-ruledef-import⑤">@import</a> rules must precede all other valid at-rules and style rules in a style sheet (ignoring <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-syntax-3/#at-ruledef-charset" id="ref-for-at-ruledef-charset">@charset</a>), or else the @import rule is invalid. The syntax of @import is: <pre class="prod">@import [ <a class="production" data-link-type="type" href="https://drafts.csswg.org/css-values-4/#url-value" id="ref-for-url-value"><url></a> <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one" id="ref-for-comb-one">|</a> <a class="production" data-link-type="type" href="https://drafts.csswg.org/css-values-4/#string-value" id="ref-for-string-value"><string></a> ] <a class="production" data-link-type="type" href="https://drafts.csswg.org/mediaqueries-4/#typedef-media-query-list" id="ref-for-typedef-media-query-list"><media-query-list></a><a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-opt" id="ref-for-mult-opt">?</a> ;</pre> Where the <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-4/#url-value" id="ref-for-url-value①"><url></a> or <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-4/#string-value" id="ref-for-string-value①"><string></a> gives the URL of the style sheet to be imported, and the optional <a class="production css" data-link-type="type" href="https://drafts.csswg.org/mediaqueries-4/#typedef-media-query-list" id="ref-for-typedef-media-query-list①"><media-query-list></a> (the <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="import-conditions">import conditions</dfn>) states the conditions under which it applies. If a <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-4/#string-value" id="ref-for-string-value②"><string></a> is provided, it must be interpreted as a <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-4/#url-value" id="ref-for-url-value②"><url></a> with the same value. <div class="example" id="example-da2e49cb"> <a class="self-link" href="#example-da2e49cb"></a> The following lines are equivalent in meaning and illustrate both <a class="css" data-link-type="maybe" href="#at-ruledef-import" id="ref-for-at-ruledef-import⑧">@import</a> syntaxes (one with <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-values-3/#funcdef-url" id="ref-for-funcdef-url">url()</a> and one with a bare string): <pre class="lang-css highlight"><c- n>@import</c-> <c- s>"mystyle.css"</c-><c- p>;</c-> <c- n>@import</c-> <c- nf>url</c-><c- p>(</c-><c- s>"mystyle.css"</c-><c- p>);</c-> </pre> </div> <h3 class="heading settled" data-level="2.1" id="conditional-import">2.1. Conditional <a class="css" data-link-type="maybe" href="#at-ruledef-import" id="ref-for-at-ruledef-import⑨">@import</a> Rules<a class="self-link" href="#conditional-import"></a></h3> The <a data-link-type="dfn" href="#import-conditions" id="ref-for-import-conditions">import conditions</a> allow the import to be media-dependent. In the absence of any import conditions, the import is unconditional. (Specifying all for the <a class="production css" data-link-type="type" href="https://drafts.csswg.org/mediaqueries-4/#typedef-media-query-list" id="ref-for-typedef-media-query-list②"><media-query-list></a> has the same effect.) If the import conditions do not match, the rules in the imported stylesheet do not apply, exactly as if the imported stylesheet were wrapped in an <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-conditional-3/#at-ruledef-media" id="ref-for-at-ruledef-media">@media</a> block with the given media query. <div class="example" id="example-5fa651f3"> <a class="self-link" href="#example-5fa651f3"></a> The following rules illustrate how <a class="css" data-link-type="maybe" href="#at-ruledef-import" id="ref-for-at-ruledef-import①⓪">@import</a> rules can be made media-dependent: <pre class="lang-css highlight"><c- n>@import</c-> <c- nf>url</c-><c- p>(</c-><c- s>"fineprint.css"</c-><c- p>)</c-> print<c- p>;</c-> <c- n>@import</c-> <c- nf>url</c-><c- p>(</c-><c- s>"bluish.css"</c-><c- p>)</c-> projection<c- p>,</c-> tv<c- p>;</c-> <c- n>@import</c-> <c- nf>url</c-><c- p>(</c-><c- s>"narrow.css"</c-><c- p>)</c-> handheld and <c- p>(</c->max-width: <c- m>400</c-><c- k>px</c-><c- p>);</c-> </pre> </div> User agents may therefore avoid fetching a media-dependent import as long as the media query does not match. The evaluation and full syntax of the <a data-link-type="dfn" href="#import-conditions" id="ref-for-import-conditions③">import conditions</a> is defined by the <a href="https://www.w3.org/TR/css3-mediaqueries/">Media Queries</a> specification <a data-link-type="biblio" href="#biblio-mediaq" title="Media Queries Level 4">[MEDIAQ]</a>. <h3 class="heading settled" data-level="2.2" id="import-processing">2.2. Processing Stylesheet Imports<a class="self-link" href="#import-processing"></a></h3> When the same style sheet is imported or linked to a document in multiple places, user agents must process (or act as though they do) each link as though the link were to an independent style sheet. Note: This does not place any requirements on resource fetching, only how the style sheet is reflected in the CSSOM and used in specs such as this one. Assuming appropriate caching, it is perfectly appropriate for a UA to fetch a style sheet only once, even though it’s linked or imported multiple times. The <a data-link-type="dfn" href="#origin" id="ref-for-origin">cascade origin</a> of an imported style sheet is the cascade origin of the style sheet that imported it. The <a data-link-type="dfn" href="https://drafts.csswg.org/css-syntax-3/#environment-encoding" id="ref-for-environment-encoding">environment encoding</a> of an imported style sheet is the encoding of the style sheet that imported it. <a data-link-type="biblio" href="#biblio-css-syntax-3" title="CSS Syntax Module Level 3">[css-syntax-3]</a> <h3 class="heading settled" data-level="2.3" id="content-type">2.3. Content-Type of CSS Style Sheets<a class="self-link" href="#content-type"></a></h3> The processing of imported style sheets depends on the actual type of the linked resource. If the resource does not have <a href="https://html.spec.whatwg.org/multipage/urls-and-fetching.html#content-type">Content-Type metadata</a>, or the host document is in <a href="https://html.spec.whatwg.org/multipage/infrastructure.html#quirks-mode">quirks mode</a> and has the <a href="https://html.spec.whatwg.org/multipage/origin.html#same-origin">same origin</a> as the imported style sheet, the type of the linked resource is <code>text/css</code>. Otherwise, the type is determined from its <a href="https://html.spec.whatwg.org/multipage/urls-and-fetching.html#content-type">Content-Type metadata</a>. If the linked resource’s type is <code>text/css</code>, it must be interpreted as a CSS style sheet. Otherwise, it must be interpreted as a network error. <h2 class="heading settled" data-level="3" id="shorthand">3. Shorthand Properties<a class="self-link" href="#shorthand"></a></h2> Some properties are <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-lt="shorthand property | shorthand" id="shorthand-property">shorthand properties</dfn>, meaning that they allow authors to specify the values of several properties with a single property. A <a data-link-type="dfn" href="#shorthand-property" id="ref-for-shorthand-property">shorthand property</a> sets all of its <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-lt="longhand | longhand property | sub-property" id="longhand">longhand sub-properties</dfn>, exactly as if expanded in place. When values are omitted from a <a data-link-type="dfn" href="#shorthand-property" id="ref-for-shorthand-property①">shorthand</a> form, unless otherwise defined, each “missing” <a data-link-type="dfn" href="#longhand" id="ref-for-longhand">sub-property</a> is assigned its <a data-link-type="dfn" href="#initial-value" id="ref-for-initial-value①">initial value</a>. <div class="note" role="note"> This means that a <a data-link-type="dfn" href="#shorthand-property" id="ref-for-shorthand-property②">shorthand</a> <a data-link-type="dfn" href="https://drafts.csswg.org/css-syntax-3/#css-property-declarations" id="ref-for-css-property-declarations①">property declaration</a> always sets all of its <a data-link-type="dfn" href="#longhand" id="ref-for-longhand①">sub-properties</a>, even those that are not explicitly set. Carelessly used, this might result in inadvertently resetting some sub-properties. Carefully used, a shorthand can guarantee a “blank slate” by resetting sub-properties inadvertently cascaded from other sources. For example, writing <a class="css" data-link-type="propdesc" href="https://drafts.csswg.org/css-backgrounds-3/#propdef-background" id="ref-for-propdef-background">background: green</a> rather than <a class="css" data-link-type="propdesc" href="https://drafts.csswg.org/css-backgrounds-3/#propdef-background-color" id="ref-for-propdef-background-color">background-color: green</a> ensures that the background color overrides any earlier <a data-link-type="dfn" href="https://drafts.csswg.org/cssom-1/#cssstyledeclaration-declarations" id="ref-for-cssstyledeclaration-declarations①">declarations</a> that might have set the background to an image with <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-backgrounds-3/#propdef-background-image" id="ref-for-propdef-background-image">background-image</a>. </div> <div class="example" id="example-8762997a"> <a class="self-link" href="#example-8762997a"></a> For example, the CSS Level 1 <a class="property css" data-link-type="property">font</a> property is a <a data-link-type="dfn" href="#shorthand-property" id="ref-for-shorthand-property④">shorthand</a> property for setting font-style, font-variant, font-weight, font-size, line-height, and font-family all at once. The multiple declarations of this example: <pre class="lang-css highlight">h1 <c- p>{</c-> <c- k>font-weight</c-><c- p>:</c-> bold<c- p>;</c-> <c- k>font-size</c-><c- p>:</c-> <c- m>12</c-><c- k>pt</c-><c- p>;</c-> <c- k>line-height</c-><c- p>:</c-> <c- m>14</c-><c- k>pt</c-><c- p>;</c-> <c- k>font-family</c-><c- p>:</c-> Helvetica<c- p>;</c-> <c- k>font-variant</c-><c- p>:</c-> normal<c- p>;</c-> <c- k>font-style</c-><c- p>:</c-> normal<c- p>;</c-> <c- p>}</c-> </pre> can therefore be rewritten as <pre class="lang-css highlight">h1 <c- p>{</c-> <c- k>font</c-><c- p>:</c-> bold <c- m>12</c-><c- k>pt</c->/<c- m>14</c-><c- k>pt</c-> Helvetica <c- p>}</c-></pre> As more <a class="property css" data-link-type="property">font</a> <a data-link-type="dfn" href="#longhand" id="ref-for-longhand④">sub-properties</a> are introduced into CSS, the shorthand declaration resets those to their initial values as well. </div> In some cases, a <a data-link-type="dfn" href="#shorthand-property" id="ref-for-shorthand-property⑤">shorthand</a> might have different syntax or special keywords that don’t directly correspond to values of its <a data-link-type="dfn" href="#longhand" id="ref-for-longhand⑤">sub-properties</a>. (In such cases, the shorthand will explicitly define the expansion of its values.) In other cases, a property might be a <dfn class="dfn-paneled" data-dfn-type="dfn" data-export id="reset-only-sub-property">reset-only sub-property</dfn> of the shorthand: Like other <a data-link-type="dfn" href="#longhand" id="ref-for-longhand⑥">sub-properties</a>, it is reset to its initial value by the shorthand when unspecified, but the shorthand might not include syntax to set the sub-property to any of its other values. For example, the <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-backgrounds-3/#propdef-border" id="ref-for-propdef-border">border</a> shorthand resets <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-backgrounds-3/#propdef-border-image" id="ref-for-propdef-border-image">border-image</a> to its initial value of none, but has no syntax to set it to anything else. <a data-link-type="biblio" href="#biblio-css-backgrounds-3" title="CSS Backgrounds and Borders Module Level 3">[css-backgrounds-3]</a> If a <a data-link-type="dfn" href="#shorthand-property" id="ref-for-shorthand-property⑦">shorthand</a> is specified as one of the <a href="https://www.w3.org/TR/css-values/#common-keywords">CSS-wide keywords</a> <a data-link-type="biblio" href="#biblio-css-values-3" title="CSS Values and Units Module Level 3">[css-values-3]</a>, it sets all of its <a data-link-type="dfn" href="#longhand" id="ref-for-longhand⑧">sub-properties</a> to that keyword, including any that are <a data-link-type="dfn" href="#reset-only-sub-property" id="ref-for-reset-only-sub-property">reset-only sub-properties</a>. (Note that these keywords cannot be combined with other values in a single <a data-link-type="dfn" href="https://drafts.csswg.org/css-syntax-3/#declaration" id="ref-for-declaration">declaration</a>, not even in a shorthand.) Declaring a <a data-link-type="dfn" href="#shorthand-property" id="ref-for-shorthand-property⑧">shorthand</a> property to be !important is equivalent to declaring all of its <a data-link-type="dfn" href="#longhand" id="ref-for-longhand⑨">sub-properties</a> to be !important. <h3 class="heading settled caniuse-paneled" data-level="3.1" id="all-shorthand">3.1. Resetting All Properties: the <a class="property css" data-link-type="property" href="#propdef-all" id="ref-for-propdef-all">all</a> property<a class="self-link" href="#all-shorthand"></a></h3> <table class="def propdef" data-link-for-hint="all"> <tbody> <tr> <th>Name: <td><dfn class="dfn-paneled css" data-dfn-type="property" data-export id="propdef-all">all</dfn> <tr class="value"> <th><a href="https://www.w3.org/TR/css-values/#value-defs">Value:</a> <td class="prod">initial <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#comb-one" id="ref-for-comb-one①">|</a> inherit | unset <tr> <th><a href="https://www.w3.org/TR/css-cascade/#initial-values">Initial:</a> <td>see individual properties <tr> <th><a href="https://www.w3.org/TR/css-cascade/#applies-to">Applies to:</a> <td>see individual properties <tr> <th><a href="https://www.w3.org/TR/css-cascade/#inherited-property">Inherited:</a> <td>see individual properties <tr> <th><a href="https://www.w3.org/TR/css-values/#percentages">Percentages:</a> <td>see individual properties <tr> <th><a href="https://www.w3.org/TR/css-cascade/#computed">Computed value:</a> <td>see individual properties <tr> <th><a href="https://www.w3.org/TR/web-animations/#animation-type">Animation type:</a> <td>see individual properties <tr> <th><a href="https://www.w3.org/TR/cssom/#serializing-css-values">Canonical order:</a> <td>per grammar </table> The <a class="property css" data-link-type="property" href="#propdef-all" id="ref-for-propdef-all①">all</a> property is a <a data-link-type="dfn" href="#shorthand-property" id="ref-for-shorthand-property⑨">shorthand</a> that resets all CSS properties except <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-writing-modes-3/#propdef-direction" id="ref-for-propdef-direction">direction</a> and <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-writing-modes-3/#propdef-unicode-bidi" id="ref-for-propdef-unicode-bidi">unicode-bidi</a>. It only accepts the <a href="https://www.w3.org/TR/css-values/#common-keywords">CSS-wide keywords</a>. It does not reset <a data-link-type="dfn" href="https://drafts.csswg.org/css-variables-2/#custom-property" id="ref-for-custom-property">custom properties</a> <a data-link-type="biblio" href="#biblio-css-variables-1" title="CSS Custom Properties for Cascading Variables Module Level 1">[css-variables-1]</a>. Note: The excepted CSS properties <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-writing-modes-3/#propdef-direction" id="ref-for-propdef-direction①">direction</a> and <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-writing-modes-3/#propdef-unicode-bidi" id="ref-for-propdef-unicode-bidi①">unicode-bidi</a> are actually markup-level features, and <a href="https://www.w3.org/TR/css-writing-modes-3/#text-direction">should not be set in the author’s style sheet</a>. (They exist as CSS properties only to style document languages not supported by the UA.) Authors should use the appropriate markup, such as HTML’s <code>dir</code> attribute, instead. <a data-link-type="biblio" href="#biblio-css-writing-modes-3" title="CSS Writing Modes Level 3">[css-writing-modes-3]</a> <div class="example" id="example-dae18981"> <a class="self-link" href="#example-dae18981"></a> For example, if an author specifies <a class="css" data-link-type="propdesc" href="#propdef-all" id="ref-for-propdef-all②">all: initial</a> on an element, it will block all inheritance and reset all properties, as if no rules appeared in the author, user, or user-agent levels of the cascade. This can be useful for the root element of a "widget" included in a page, which does not wish to inherit the styles of the outer page. Note, however, that any "default" style applied to that element (such as, e.g. <a class="css" data-link-type="propdesc" href="https://drafts.csswg.org/css2/#propdef-display" id="ref-for-propdef-display">display: block</a> from the UA style sheet on block elements such as <code><div></code>) will also be blown away. </div> <h2 class="heading settled" data-level="4" id="value-stages">4. Value Processing<a class="self-link" href="#value-stages"></a></h2> Once a user agent has parsed a document and constructed a document tree, it must assign, to every element in the tree, and correspondingly to every box in the formatting structure, a value to every property that applies to the target media type. The final value of a CSS property for a given element or box is the result of a multi-step calculation: <ol> <li> First, all the <a data-link-type="dfn" href="#declared-value" id="ref-for-declared-value">declared values</a> applied to an element are collected, for each property on each element. There may be zero or many declared values applied to the element. <li> Cascading yields the <a data-link-type="dfn" href="#cascaded-value" id="ref-for-cascaded-value">cascaded value</a>. There is at most one cascaded value per property per element. <li> Defaulting yields the <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value①">specified value</a>. Every element has exactly one specified value per property. <li> Resolving value dependencies yields the <a data-link-type="dfn" href="#computed-value" id="ref-for-computed-value">computed value</a>. Every element has exactly one computed value per property. <li> Formatting the document yields the <a data-link-type="dfn" href="#used-value" id="ref-for-used-value">used value</a>. An element only has a used value for a given property if that property applies to the element. <li> Finally, the used value is transformed to the <a data-link-type="dfn" href="#actual-value" id="ref-for-actual-value">actual value</a> based on constraints of the display environment. As with the <a data-link-type="dfn" href="#used-value" id="ref-for-used-value②">used value</a>, there may or may not be an actual value for a given property on an element. </ol> <h3 class="heading settled" data-level="4.1" id="declared">4.1. Declared Values<a class="self-link" href="#declared"></a></h3> Each property declaration <a href="#filtering">applied to an element</a> contributes a <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-local-lt="declared" id="declared-value">declared value</dfn> for that property associated with the element. See <a href="#filtering">Filtering Declarations</a> for details. These values are then processed by the <a data-link-type="dfn" href="#cascade" id="ref-for-cascade①">cascade</a> to choose a single “winning value”. <h3 class="heading settled" data-level="4.2" id="cascaded">4.2. Cascaded Values<a class="self-link" href="#cascaded"></a></h3> The <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-local-lt="cascaded" id="cascaded-value">cascaded value</dfn> represents the result of <a href="#cascade" id="ref-for-cascade①①">the cascade</a>: it is the <a data-link-type="dfn" href="#declared-value" id="ref-for-declared-value②">declared value</a> that wins the cascade (is sorted first in the <a data-link-type="dfn" href="#output-of-the-cascade" id="ref-for-output-of-the-cascade">output of the cascade</a>). If the output of the cascade is an empty list, there is no <a data-link-type="dfn" href="#cascaded-value" id="ref-for-cascaded-value②">cascaded value</a>. <h3 class="heading settled" data-level="4.3" id="specified">4.3. Specified Values<a class="self-link" href="#specified"></a></h3> The <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-local-lt="specified" id="specified-value">specified value</dfn> is the value of a given property that the style sheet authors intended for that element. It is the result of putting the <a data-link-type="dfn" href="#cascaded-value" id="ref-for-cascaded-value③">cascaded value</a> through the <a href="#defaulting">defaulting</a> processes, guaranteeing that a <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value③">specified value</a> exists for every property on every element. In many cases, the <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value④">specified value</a> is the <a data-link-type="dfn" href="#cascaded-value" id="ref-for-cascaded-value④">cascaded value</a>. However, if there is no cascaded value at all, the specified value is <a href="#defaulting">defaulted</a>. The <a data-link-type="dfn" href="https://drafts.csswg.org/css-values-3/#css-wide-keywords" id="ref-for-css-wide-keywords">CSS-wide keywords</a> are handled specially when they are the cascaded value of a property, setting the specified value as required by that keyword, see <a href="#defaulting-keywords">§ 7.3 Explicit Defaulting</a>. <h3 class="heading settled" data-level="4.4" id="computed">4.4. Computed Values<a class="self-link" href="#computed"></a></h3> The <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-local-lt="computed" id="computed-value">computed value</dfn> is the result of resolving the <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value⑦">specified value</a> as defined in the “Computed Value” line of the property definition table, generally absolutizing it in preparation for <a data-link-type="dfn" href="#css-inheritance" id="ref-for-css-inheritance①">inheritance</a>. Note: The <a data-link-type="dfn" href="#computed-value" id="ref-for-computed-value②">computed value</a> is the value that is transferred from parent to child during <a data-link-type="dfn" href="#css-inheritance" id="ref-for-css-inheritance②">inheritance</a>. For historical reasons, it is not necessarily the value returned by the <code class="idl"><a data-link-type="idl" href="https://drafts.csswg.org/cssom-1/#dom-window-getcomputedstyle" id="ref-for-dom-window-getcomputedstyle">getComputedStyle()</a></code> function, which sometimes returns <a data-link-type="dfn" href="#used-value" id="ref-for-used-value③">used values</a>. <a data-link-type="biblio" href="#biblio-cssom" title="CSS Object Model (CSSOM)">[CSSOM]</a> Furthermore, the computed value is an abstract data representation: their definitions reflect that data representation, not how that data is serialized. For example, serialization rules often allow omitting certain values which are implied during parsing; but those values are nonetheless part of the computed value. <div class="example" id="example-29410c97"> <a class="self-link" href="#example-29410c97"></a> A <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value⑧">specified value</a> can be either absolute (i.e., not relative to another value, as in <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css2/#valdef-color-red" id="ref-for-valdef-color-red①">red</a> or 2mm) or relative (i.e., relative to another value, as in <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-align-3/#valdef-align-self-auto" id="ref-for-valdef-align-self-auto">auto</a>, 2em). Computing a relative value generally absolutizes it: <ul> <li> values with relative units (<a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-values-3/#em" id="ref-for-em">em</a>, <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-values-3/#ex" id="ref-for-ex">ex</a>, <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-values-3/#vh" id="ref-for-vh">vh</a>, <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-values-3/#vw" id="ref-for-vw">vw</a>) must be made absolute by multiplying with the appropriate reference size <li> certain keywords (e.g., smaller, bolder) must be replaced according to their definitions <li> percentages on some properties must be multiplied by a reference value (defined by the property) <li> valid relative URLs must be resolved to become absolute. </ul> See examples (f), (g) and (h) in the <a href="#stages-examples">table below</a>. </div> Note: In general, the <a data-link-type="dfn" href="#computed-value" id="ref-for-computed-value⑤">computed value</a> resolves the <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value⑨">specified value</a> as far as possible without laying out the document or performing other expensive or hard-to-parallelize operations, such as resolving network requests or retrieving values other than from the element and its parent. The <a data-link-type="dfn" href="#computed-value" id="ref-for-computed-value⑥">computed value</a> exists even when the property does not apply. However, some properties may change how they determine the computed value based on whether the property <a data-link-type="dfn" href="#applies-to" id="ref-for-applies-to">applies to</a> the element. <h3 class="heading settled" data-level="4.5" id="used">4.5. Used Values<a class="self-link" href="#used"></a></h3> The <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-local-lt="used" id="used-value">used value</dfn> is the result of taking the <a data-link-type="dfn" href="#computed-value" id="ref-for-computed-value⑧">computed value</a> and completing any remaining calculations to make it the absolute theoretical value used in the formatting of the document. The effect of the <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-viewport/#propdef-zoom" id="ref-for-propdef-zoom">zoom</a> property is applied during this stage, and before any calculations that require layout. <a class="self-link" href="#example-aaa6b50b"></a> For example, a declaration of <a class="css" data-link-type="propdesc" href="https://drafts.csswg.org/css-sizing-3/#propdef-width" id="ref-for-propdef-width">width: auto</a> can’t be resolved into a length without knowing the layout of the element’s ancestors, so the <a data-link-type="dfn" href="#computed-value" id="ref-for-computed-value⑨">computed value</a> is <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-align-3/#valdef-align-self-auto" id="ref-for-valdef-align-self-auto①">auto</a>, while the <a data-link-type="dfn" href="#used-value" id="ref-for-used-value④">used value</a> is an absolute length, such as 100px. <a data-link-type="biblio" href="#biblio-css2" title="Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification">[CSS2]</a> <a class="self-link" href="#example-aac2d669"></a> As another example, a <code><div></code> might have a computed <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-break-3/#propdef-break-before" id="ref-for-propdef-break-before">break-before</a> value of <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-align-3/#valdef-align-self-auto" id="ref-for-valdef-align-self-auto②">auto</a>, but acquire a used break-before value of <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-break-4/#valdef-break-before-page" id="ref-for-valdef-break-before-page">page</a> by propagation from its first child. <a data-link-type="biblio" href="#biblio-css-break-3" title="CSS Fragmentation Module Level 3">[css-break-3]</a> If a property does not <dfn class="dfn-paneled" data-dfn-type="dfn" data-lt="applies to | apply to" data-noexport id="applies-to">apply to</dfn> this element or box type—as noted in its “Applies to” line—then does not directly take effect on that type of box or element, and therefore has no <a data-link-type="dfn" href="#used-value" id="ref-for-used-value⑤">used value</a> for that property. <a class="self-link" href="#example-19a1092f"></a> For example, the <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-flexbox-1/#propdef-flex" id="ref-for-propdef-flex">flex</a> property has no <a data-link-type="dfn" href="#used-value" id="ref-for-used-value⑥">used value</a> on elements that aren’t <a data-link-type="dfn" href="https://drafts.csswg.org/css-flexbox-1/#flex-item" id="ref-for-flex-item">flex items</a>. Note: A property defined to apply to “all elements” applies to all elements and <a data-link-type="dfn" href="https://drafts.csswg.org/css-display-4/#display-type" id="ref-for-display-type">display types</a>, but not necessarily to all <a data-link-type="dfn" href="https://drafts.csswg.org/selectors-4/#pseudo-element" id="ref-for-pseudo-element">pseudo-element</a> types, since pseudo-elements often have their own specific rendering models or other restrictions. The <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-pseudo-4/#selectordef-before" id="ref-for-selectordef-before">::before</a> and <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-pseudo-4/#selectordef-after" id="ref-for-selectordef-after">::after</a> pseudo-elements, however, are defined to generate boxes almost exactly like normal elements and are therefore defined accept all properties that apply to “all elements”. See <a data-link-type="biblio" href="#biblio-css-pseudo-4" title="CSS Pseudo-Elements Module Level 4">[CSS-PSEUDO-4]</a> for more information about <a data-link-type="dfn" href="https://www.w3.org/TR/CSS2/selector.html#x22" id="ref-for-x22">pseudo-elements</a>. <h3 class="heading settled" data-level="4.6" id="actual">4.6. Actual Values<a class="self-link" href="#actual"></a></h3> A <a data-link-type="dfn" href="#used-value" id="ref-for-used-value⑦">used value</a> is in principle ready to be used, but a user agent may not be able to make use of the value in a given environment. For example, a user agent may only be able to render borders with integer pixel widths and may therefore have to approximate the <a data-link-type="dfn" href="#used-value" id="ref-for-used-value⑧">used</a> width. Also, the font size of an element may need adjustment based on the availability of fonts or the value of the <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-fonts-5/#propdef-font-size-adjust" id="ref-for-propdef-font-size-adjust">font-size-adjust</a> property. The <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-local-lt="actual" id="actual-value">actual value</dfn> is the used value after any such adjustments have been made. Note: By probing the actual values of elements, much can be learned about how the document is laid out. However, not all information is recorded in the actual values. For example, the actual value of the <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css2/#propdef-page-break-after" id="ref-for-propdef-page-break-after">page-break-after</a> property does not reflect whether there is a page break or not after the element. Similarly, the actual value of <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-break-3/#propdef-orphans" id="ref-for-propdef-orphans">orphans</a> does not reflect how many orphan lines there is in a certain element. See examples (j) and (k) in the <a href="#stages-examples">table below</a>. <h3 class="heading settled" data-level="4.7" id="stages-examples">4.7. Examples<a class="self-link" href="#stages-examples"></a></h3> <table class="data non-normative"> <caption>Examples of CSS Value Computation</caption> <thead> <tr> <th> <th>Property <th>Winning declaration <th>Cascaded value <th>Specified value <th>Computed value <th>Used value <th>Actual value <tbody> <tr> <td>(a) <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-text-3/#propdef-text-align" id="ref-for-propdef-text-align">text-align</a> <td><code class="declaration">text-align: left</code> <td>left <td>left <td>left <td>left <td>left <tr> <td>(b) <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-backgrounds-3/#propdef-border-top-width" id="ref-for-propdef-border-top-width">border-top-width</a>, <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-backgrounds-3/#propdef-border-right-width" id="ref-for-propdef-border-right-width">border-right-width</a>, <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-backgrounds-3/#propdef-border-bottom-width" id="ref-for-propdef-border-bottom-width">border-bottom-width</a>, <a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-backgrounds-3/#propdef-border-left-width" id="ref-for-propdef-border-left-width">border-left-width</a> <td><code class="declaration">border-width: inherit</code> <td>inherit <td class="say">4.2px <td>4.2px <td>4.2px <td>4px <tr> <td>(c) <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-sizing-3/#propdef-width" id="ref-for-propdef-width①">width</a> <td>(none) <td>(none) <td>auto (initial value) <td>auto <td>120px <td>120px <tr> <td>(d) <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-lists-3/#propdef-list-style-position" id="ref-for-propdef-list-style-position">list-style-position</a> <td><code class="declaration">list-style-position: inherit</code> <td>inherit <td class="say">inside <td>inside <td>inside <td>inside <tr> <td>(e) <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-lists-3/#propdef-list-style-position" id="ref-for-propdef-list-style-position①">list-style-position</a> <td><code class="declaration">list-style-position: initial</code> <td>initial <td>outside (initial value) <td>outside <td>outside <td>outside <tr> <td>(f) <th><a class="property css" data-link-type="property">font-size</a> <td><code class="declaration">font-size: 1.2em</code> <td>1.2em <td>1.2em <td class="say">14.1px <td>14.1px <td>14px <tr> <td>(g) <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-sizing-3/#propdef-width" id="ref-for-propdef-width②">width</a> <td><code class="declaration">width: 80%</code> <td>80% <td>80% <td>80% <td class="say">354.2px <td>354px <tr> <td>(h) <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-sizing-3/#propdef-width" id="ref-for-propdef-width③">width</a> <td><code class="declaration">width: auto</code> <td>auto <td>auto <td>auto <td class="say">134px <td>134px <tr> <td>(i) <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-sizing-3/#propdef-height" id="ref-for-propdef-height">height</a> <td><code class="declaration">height: auto</code> <td>auto <td>auto <td>auto <td class="say">176px <td>176px <tr> <td>(j) <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css2/#propdef-page-break-after" id="ref-for-propdef-page-break-after①">page-break-after</a> <td>(none) <td>(none) <td>auto (initial value) <td>auto <td>auto <td>auto <tr> <td>(k) <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-break-3/#propdef-orphans" id="ref-for-propdef-orphans①">orphans</a> <td><code class="declaration">orphans: 3</code> <td>3 <td>3 <td>3 <td>3 <td>3 </table> <h2 class="heading settled" data-level="5" id="filtering">5. Filtering<a class="self-link" href="#filtering"></a></h2> In order to find the <a data-link-type="dfn" href="#declared-value" id="ref-for-declared-value③">declared values</a>, implementations must first identify all <a data-link-type="dfn" href="https://drafts.csswg.org/cssom-1/#cssstyledeclaration-declarations" id="ref-for-cssstyledeclaration-declarations②">declarations</a> that apply to each element. A declaration applies to an element if: <ul> <li> It belongs to a style sheet that currently applies to this document. <li> It is not qualified by a conditional rule <a data-link-type="biblio" href="#biblio-css-conditional-3" title="CSS Conditional Rules Module Level 3">[CSS-CONDITIONAL-3]</a> with a false condition. <li> It belongs to a style rule whose selector matches the element. <a data-link-type="biblio" href="#biblio-select" title="Selectors Level 3">[SELECT]</a> <li> It is syntactically valid: the declaration’s property is a known property name, and the declaration’s value matches the syntax for that property. </ul> The values of the <a data-link-type="dfn" href="https://drafts.csswg.org/cssom-1/#cssstyledeclaration-declarations" id="ref-for-cssstyledeclaration-declarations③">declarations</a> that apply form, for each property on each element, a list of <a data-link-type="dfn" href="#declared-value" id="ref-for-declared-value④">declared values</a>. The next section, the <a data-link-type="dfn" href="#cascade" id="ref-for-cascade②">cascade</a>, prioritizes these lists. <h2 class="heading settled" data-level="6" id="cascading">6. Cascading<a class="self-link" href="#cascading"></a></h2> The <dfn class="dfn-paneled" data-dfn-type="dfn" data-export id="cascade">cascade</dfn> takes an unordered list of <a data-link-type="dfn" href="#declared-value" id="ref-for-declared-value⑤">declared values</a> for a given property on a given element, sorts them by their <a data-link-type="dfn" href="https://drafts.csswg.org/css-syntax-3/#declaration" id="ref-for-declaration①">declaration’s</a> precedence as determined below, and outputs a single <a data-link-type="dfn" href="#cascaded-value" id="ref-for-cascaded-value⑦">cascaded value</a>. <h3 class="heading settled" data-level="6.1" id="cascade-sort">6.1. Cascade Sorting Order<a class="self-link" href="#cascade-sort"></a></h3> The cascade sorts <a data-link-type="dfn" href="https://drafts.csswg.org/cssom-1/#cssstyledeclaration-declarations" id="ref-for-cssstyledeclaration-declarations④">declarations</a> according to the following criteria, in descending order of precedence: <dl> <dt id="cascade-origin"><a class="self-link" href="#cascade-origin"></a>Origin and Importance <dd> The <a data-link-type="dfn" href="#origin" id="ref-for-origin②">origin</a> of a <a data-link-type="dfn" href="https://drafts.csswg.org/css-syntax-3/#declaration" id="ref-for-declaration②">declaration</a> is based on where it comes from and its <a data-link-type="dfn" href="#important" id="ref-for-important">importance</a> is whether or not it is declared with !important (see <a href="#importance">below</a>). The precedence of the various origins is, in descending order: <ol> <li>Transition declarations <a data-link-type="biblio" href="#biblio-css-transitions-1" title="CSS Transitions">[css-transitions-1]</a> <li><a data-link-type="dfn" href="#important" id="ref-for-important①">Important</a> <a data-link-type="dfn" href="#cascade-origin-ua" id="ref-for-cascade-origin-ua">user agent</a> declarations <li><a data-link-type="dfn" href="#important" id="ref-for-important②">Important</a> <a data-link-type="dfn" href="#cascade-origin-user" id="ref-for-cascade-origin-user">user</a> declarations <li><a data-link-type="dfn" href="#important" id="ref-for-important③">Important</a> <a data-link-type="dfn" href="#cascade-origin-author" id="ref-for-cascade-origin-author">author</a> declarations <li>Animation declarations <a data-link-type="biblio" href="#biblio-css-animations-1" title="CSS Animations Level 1">[css-animations-1]</a> <li><a data-link-type="dfn" href="#normal" id="ref-for-normal">Normal</a> <a data-link-type="dfn" href="#cascade-origin-author" id="ref-for-cascade-origin-author①">author</a> declarations <li><a data-link-type="dfn" href="#normal" id="ref-for-normal①">Normal</a> <a data-link-type="dfn" href="#cascade-origin-user" id="ref-for-cascade-origin-user①">user</a> declarations <li><a data-link-type="dfn" href="#normal" id="ref-for-normal②">Normal</a> <a data-link-type="dfn" href="#cascade-origin-ua" id="ref-for-cascade-origin-ua①">user agent</a> declarations </ol> Declarations from <a data-link-type="dfn" href="#origin" id="ref-for-origin④">origins</a> earlier in this list win over declarations from later origins. <dt id="cascade-specificity"><a class="self-link" href="#cascade-specificity"></a>Specificity <dd> The <a href="https://www.w3.org/TR/selectors/#specificity">Selectors module</a> <a data-link-type="biblio" href="#biblio-select" title="Selectors Level 3">[SELECT]</a> describes how to compute the specificity of a selector. Each declaration has the same specificity as the style rule it appears in. For the purpose of this step, declarations that do not belong to a style rule (such as the <a href="https://www.w3.org/TR/css-style-attr/#interpret">contents of a style attribute</a>) are considered to have a specificity higher than any selector. The declaration with the highest specificity wins. <dt id="cascade-order"><a class="self-link" href="#cascade-order"></a>Order of Appearance <dd> The last declaration in document order wins. For this purpose: <ul> <li>Declarations from <a class="css" data-link-type="at-rule" href="#at-ruledef-import" id="ref-for-at-ruledef-import①①">imported style sheets</a> are ordered as if their style sheets were substituted in place of the @import rule. <li>Declarations from style sheets independently linked by the originating document are treated as if they were concatenated in linking order, as determined by the host document language. <li>Declarations from style attributes are ordered according to the document order of the element the style attribute appears on, and are all placed after any style sheets. <a data-link-type="biblio" href="#biblio-cssstyleattr" title="CSS Style Attributes">[CSSSTYLEATTR]</a> </ul> </dl> The <dfn class="dfn-paneled" data-dfn-type="dfn" data-export id="output-of-the-cascade">output of the cascade</dfn> is a (potentially empty) sorted list of <a data-link-type="dfn" href="#declared-value" id="ref-for-declared-value⑥">declared values</a> for each property on each element. <h3 class="heading settled" data-level="6.2" id="cascading-origins">6.2. Cascading Origins<a class="self-link" href="#cascading-origins"></a></h3> Each style rule has a <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-local-lt="origin" id="origin">cascade origin</dfn>, which determines where it enters the cascade. CSS defines three core <a data-link-type="dfn" href="#origin" id="ref-for-origin⑥">origins</a>: <dl> <dt><dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-lt="author origin|author style sheet|author-origin" id="cascade-origin-author">Author Origin</dfn> <dd> The author specifies style sheets for a source document according to the conventions of the document language. For instance, in HTML, style sheets may be included in the document or linked externally. <dt><dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-lt="user origin|user style sheet|user-origin" id="cascade-origin-user">User Origin</dfn> <dd> The user may be able to specify style information for a particular document. For example, the user may specify a file that contains a style sheet or the user agent may provide an interface that generates a user style sheet (or behaves as if it did). <dt><dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-lt="user-agent origin|UA origin|user-agent style sheet|UA style sheet|UA-origin" id="cascade-origin-ua">User-Agent Origin</dfn> <dd> Conforming user agents must apply a default style sheet (or behave as if they did). A user agent’s default style sheet should present the elements of the document language in ways that satisfy general presentation expectations for the document language (e.g., for visual browsers, the EM element in HTML is presented using an italic font). See e.g. the <a href="https://html.spec.whatwg.org/multipage/rendering.html#the-css-user-agent-style-sheet-and-presentational-hints">HTML user agent style sheet</a>. <a data-link-type="biblio" href="#biblio-html" title="HTML Standard">[HTML]</a> </dl> Extensions to CSS define the following additional <a data-link-type="dfn" href="#origin" id="ref-for-origin⑦">origins</a>: <dl> <dt><dfn class="dfn-paneled" data-dfn-type="dfn" data-export id="cascade-origin-animation">Animation Origin</dfn> <dd> CSS Animations <a data-link-type="biblio" href="#biblio-css-animations-1" title="CSS Animations Level 1">[css-animations-1]</a> generate “virtual” rules representing their effects when running. <dt><dfn class="dfn-paneled" data-dfn-type="dfn" data-export id="cascade-origin-transition">Transition Origin</dfn> <dd> Like CSS Animations, CSS Transitions <a data-link-type="biblio" href="#biblio-css-transitions-1" title="CSS Transitions">[css-transitions-1]</a> generate “virtual” rules representing their effects when running. </dl> <h3 class="heading settled" data-level="6.3" id="importance">6.3. Important Declarations: the !important annotation<a class="self-link" href="#importance"></a></h3> CSS attempts to create a balance of power between author and user style sheets. By default, rules in an author’s style sheet override those in a user’s style sheet, which override those in the user-agent’s default style sheet. To balance this, a <a data-link-type="dfn" href="https://drafts.csswg.org/css-syntax-3/#declaration" id="ref-for-declaration③">declaration</a> can be marked <a data-link-type="dfn" href="#important" id="ref-for-important④">important</a>, which increases its weight in the cascade and inverts the order of precedence. A <a data-link-type="dfn" href="https://drafts.csswg.org/css-syntax-3/#declaration" id="ref-for-declaration④">declaration</a> is <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-local-lt="importance" id="important">important</dfn> if it has a !important annotation as defined by <a data-link-type="biblio" href="#biblio-css-syntax-3" title="CSS Syntax Module Level 3">[css-syntax-3]</a>, i.e. if the last two (non-whitespace, non-comment) tokens in its value are the delimiter token ! followed by the identifier token important. All other declarations are <dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="normal">normal</dfn> (non-<a data-link-type="dfn" href="#important" id="ref-for-important⑤">important</a>). <div class="example" id="example-813b5c64"> <a class="self-link" href="#example-813b5c64"></a> <pre class="lang-css highlight"><c- p>[</c->hidden<c- p>]</c-> <c- p>{</c-> <c- k>display</c-><c- p>:</c-> none !important<c- p>;</c-> <c- p>}</c-></pre> </div> An <a data-link-type="dfn" href="#important" id="ref-for-important⑥">important</a> declaration takes precedence over a <a data-link-type="dfn" href="#normal" id="ref-for-normal③">normal</a> declaration. Author and user style sheets may contain important declarations, with <a data-link-type="dfn" href="#cascade-origin-user" id="ref-for-cascade-origin-user②">user-origin</a> important declarations overriding <a data-link-type="dfn" href="#cascade-origin-author" id="ref-for-cascade-origin-author②">author-origin</a> important declarations. This CSS feature improves accessibility of documents by giving users with special requirements (large fonts, color combinations, etc.) control over presentation. <a data-link-type="dfn" href="#important" id="ref-for-important①⓪">Important</a> declarations from all origins take precedence over animations. This allows authors to override animated values in important cases. (Animated values normally override all other rules.) <a data-link-type="biblio" href="#biblio-css-animations-1" title="CSS Animations Level 1">[css-animations-1]</a> <a data-link-type="dfn" href="#cascade-origin-ua" id="ref-for-cascade-origin-ua②">User-agent style sheets</a> may also contain <a data-link-type="dfn" href="#important" id="ref-for-important①①">important</a> declarations. These override all <a data-link-type="dfn" href="#cascade-origin-author" id="ref-for-cascade-origin-author③">author</a> and <a data-link-type="dfn" href="#cascade-origin-user" id="ref-for-cascade-origin-user③">user</a> declarations. <div class="example" id="example-b189d121"> <a class="self-link" href="#example-b189d121"></a> The first rule in the user’s style sheet in the following example contains an !important declaration, which overrides the corresponding declaration in the author’s style sheet. The declaration in the second rule will also win due to being marked !important. However, the third declaration in the user’s style sheet is not !important and will therefore lose to the second rule in the author’s style sheet (which happens to set style on a <a data-link-type="dfn" href="#shorthand-property" id="ref-for-shorthand-property①⓪">shorthand</a> property). Also, the third author rule will lose to the second author rule since the second declaration is !important. This shows that !important declarations have a function also within author style sheets. <pre class="lang-css highlight"><c- c>/* From the user’s style sheet */</c-> p <c- p>{</c-> <c- k>text-indent</c-><c- p>:</c-> <c- m>1</c-><c- k>em</c-> !important <c- p>}</c-> p <c- p>{</c-> <c- k>font-style</c-><c- p>:</c-> italic !important <c- p>}</c-> p <c- p>{</c-> <c- k>font-size</c-><c- p>:</c-> <c- m>18</c-><c- k>pt</c-> <c- p>}</c-> <c- c>/* From the author’s style sheet */</c-> p <c- p>{</c-> <c- k>text-indent</c-><c- p>:</c-> <c- m>1.5</c-><c- k>em</c-> !important <c- p>}</c-> p <c- p>{</c-> <c- k>font</c-><c- p>:</c-> normal <c- m>12</c-><c- k>pt</c-> sans-serif !important <c- p>}</c-> p <c- p>{</c-> <c- k>font-size</c-><c- p>:</c-> <c- m>24</c-><c- k>pt</c-> <c- p>}</c-> </pre> <table class="data"> <thead> <tr> <th>Property <th>Winning value <tbody> <tr> <th><a class="property css" data-link-type="property" href="https://drafts.csswg.org/css-text-4/#propdef-text-indent" id="ref-for-propdef-text-indent">text-indent</a> <td>1em <tr> <th><a class="property css" data-link-type="property">font-style</a> <td>italic <tr> <th><a class="property css" data-link-type="property">font-size</a> <td>12pt <tr> <th><a class="property css" data-link-type="property">font-family</a> <td>sans-serif </table> </div> <h3 class="heading settled" data-level="6.4" id="preshint">6.4. Precedence of Non-CSS Presentational Hints<a class="self-link" href="#preshint"></a></h3> The UA may choose to honor presentational hints in a source document’s markup, for example the <code>bgcolor</code> attribute or <code><a data-link-type="element" href="https://html.spec.whatwg.org/multipage/text-level-semantics.html#the-s-element" id="ref-for-the-s-element">s</a></code> element in <a data-link-type="biblio" href="#biblio-html" title="HTML Standard">[HTML]</a>. All document language-based styling must be translated to corresponding CSS rules and either enter the cascade as <a data-link-type="dfn" href="#cascade-origin-ua" id="ref-for-cascade-origin-ua③">UA-origin</a> rules or be treated as <a data-link-type="dfn" href="#cascade-origin-author" id="ref-for-cascade-origin-author④">author-origin</a> rules with a specificity of zero placed at the start of the author style sheet. A document language may define whether such a presentational hint enters the <a data-link-type="dfn" href="#cascade" id="ref-for-cascade③">cascade</a> as UA-origin or author-origin; if so, the UA must behave accordingly. For example, <a data-link-type="biblio" href="#biblio-svg11" title="Scalable Vector Graphics (SVG) 1.1 (Second Edition)">[SVG11]</a> maps its presentation attributes into the author level. Note: Presentational hints entering the <a data-link-type="dfn" href="#cascade" id="ref-for-cascade④">cascade</a> as <a data-link-type="dfn" href="#cascade-origin-ua" id="ref-for-cascade-origin-ua⑤">UA-origin</a> rules can be overridden by <a data-link-type="dfn" href="#cascade-origin-author" id="ref-for-cascade-origin-author⑦">author-origin</a> or <a data-link-type="dfn" href="#cascade-origin-user" id="ref-for-cascade-origin-user④">user-origin</a> styles. Presentational hints entering the cascade as author-origin rules can be overridden by author-origin styles, but not by non-important user-origin styles. Host languages should choose the appropriate origin for presentational hints with these considerations in mind. <h2 class="heading settled" data-level="7" id="defaulting">7. Defaulting<a class="self-link" href="#defaulting"></a></h2> When the <a data-link-type="dfn" href="#cascade" id="ref-for-cascade⑤">cascade</a> does not result in a value, the <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value①⓪">specified value</a> must be found some other way. <a data-link-type="dfn" href="#inherited-property" id="ref-for-inherited-property">Inherited properties</a> draw their defaults from their parent element through <a data-link-type="dfn" href="#css-inheritance" id="ref-for-css-inheritance③">inheritance</a>; all other properties take their <a data-link-type="dfn" href="#initial-value" id="ref-for-initial-value②">initial value</a>. Authors can explicitly request inheritance or initialization via the <a class="css" data-link-type="maybe" href="#valdef-all-inherit" id="ref-for-valdef-all-inherit">inherit</a> and <a class="css" data-link-type="maybe" href="#valdef-all-initial" id="ref-for-valdef-all-initial">initial</a> keywords. <h3 class="heading settled" data-level="7.1" id="initial-values">7.1. Initial Values<a class="self-link" href="#initial-values"></a></h3> Each property has an <dfn class="dfn-paneled" data-dfn-type="dfn" data-export id="initial-value">initial value</dfn>, defined in the property’s definition table. If the property is not an <a data-link-type="dfn" href="#inherited-property" id="ref-for-inherited-property①">inherited property</a>, and the <a data-link-type="dfn" href="#cascade" id="ref-for-cascade⑥">cascade</a> does not result in a value, then the <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value①①">specified value</a> of the property is its <a data-link-type="dfn" href="#initial-value" id="ref-for-initial-value③">initial value</a>. <h3 class="heading settled" data-level="7.2" id="inheriting">7.2. Inheritance<a class="self-link" href="#inheriting"></a></h3> <dfn class="dfn-paneled" data-dfn-for="CSS" data-dfn-type="dfn" data-export data-lt="inheritance|inherit" id="css-inheritance">Inheritance</dfn> propagates property values from parent elements to their children. The <dfn class="dfn-paneled" data-dfn-type="dfn" data-export id="inherited-value">inherited value</dfn> of a property on an element is the <a data-link-type="dfn" href="#computed-value" id="ref-for-computed-value①⓪">computed value</a> of the property on the element’s parent element. For the root element, which has no parent element, the <a data-link-type="dfn" href="#inherited-value" id="ref-for-inherited-value">inherited value</a> is the <a data-link-type="dfn" href="#initial-value" id="ref-for-initial-value④">initial value</a> of the property. <a data-link-type="dfn" href="https://www.w3.org/TR/CSS2/selector.html#x22" id="ref-for-x22①">Pseudo-elements</a> inherit according to the fictional tag sequence described for each <a data-link-type="dfn" href="https://drafts.csswg.org/selectors-4/#pseudo-element" id="ref-for-pseudo-element①">pseudo-element</a>. <a data-link-type="biblio" href="#biblio-select" title="Selectors Level 3">[SELECT]</a> Some properties are <dfn class="dfn-paneled" data-dfn-type="dfn" data-export data-lt="inherited property" id="inherited-property">inherited properties</dfn>, as defined in their property definition table. This means that, unless the <a data-link-type="dfn" href="#cascade" id="ref-for-cascade⑦">cascade</a> results in a value, the value will be determined by <a data-link-type="dfn" href="#css-inheritance" id="ref-for-css-inheritance④">inheritance</a>. A property can also be explicitly inherited. See the <a class="css" data-link-type="maybe" href="#valdef-all-inherit" id="ref-for-valdef-all-inherit①">inherit</a> keyword. Note: Inheritance follows the document tree and is not intercepted by <a href="https://www.w3.org/TR/CSS2/visuren.html#box-gen">anonymous boxes</a>, or otherwise affected by manipulations of the box tree. <h3 class="heading settled" data-level="7.3" id="defaulting-keywords">7.3. Explicit Defaulting<a class="self-link" href="#defaulting-keywords"></a></h3> Several CSS-wide property values are defined below; declaring a property to have these values explicitly specifies a particular defaulting behavior. As specified in <a href="https://www.w3.org/TR/css-values/#common-keywords">CSS Values and Units</a> <a data-link-type="biblio" href="#biblio-css-values-3" title="CSS Values and Units Module Level 3">[css-values-3]</a>, all CSS properties can accept these values. <h4 class="heading settled caniuse-paneled" data-level="7.3.1" id="initial">7.3.1. Resetting a Property: the <a class="css" data-link-type="maybe" href="#valdef-all-initial" id="ref-for-valdef-all-initial①">initial</a> keyword<a class="self-link" href="#initial"></a></h4> The <dfn class="dfn-paneled css" data-dfn-for="all" data-dfn-type="value" data-export id="valdef-all-initial">initial</dfn> <a data-link-type="dfn" href="https://drafts.csswg.org/css-values-3/#css-wide-keywords" id="ref-for-css-wide-keywords①">CSS-wide keyword</a> represents the value defined as the property’s <a data-link-type="dfn" href="#initial-value" id="ref-for-initial-value⑤">initial value</a>. If the <a data-link-type="dfn" href="#cascaded-value" id="ref-for-cascaded-value⑧">cascaded value</a> of a property is the <a class="css" data-link-type="maybe" href="#valdef-all-initial" id="ref-for-valdef-all-initial②">initial</a> keyword, the property’s <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value①②">specified value</a> is its <a data-link-type="dfn" href="#initial-value" id="ref-for-initial-value⑥">initial value</a>. <h4 class="heading settled" data-level="7.3.2" id="inherit">7.3.2. Explicit Inheritance: the <a class="css" data-link-type="maybe" href="#valdef-all-inherit" id="ref-for-valdef-all-inherit②">inherit</a> keyword<a class="self-link" href="#inherit"></a></h4> The <dfn class="dfn-paneled css" data-dfn-for="all" data-dfn-type="value" data-export id="valdef-all-inherit">inherit</dfn> <a data-link-type="dfn" href="https://drafts.csswg.org/css-values-3/#css-wide-keywords" id="ref-for-css-wide-keywords②">CSS-wide keyword</a> represents the property’s <a data-link-type="dfn" href="#computed-value" id="ref-for-computed-value①①">computed value</a> on the parent element. If the <a data-link-type="dfn" href="#cascaded-value" id="ref-for-cascaded-value⑨">cascaded value</a> of a property is the <a class="css" data-link-type="maybe" href="#valdef-all-inherit" id="ref-for-valdef-all-inherit③">inherit</a> keyword, the property’s <a data-link-type="dfn" href="#specified-value" id="ref-for-specified-value①③">specified</a> and <a data-link-type="dfn" href="#computed-value" id="ref-for-computed-value①②">computed values</a> are the <a data-link-type="dfn" href="#inherited-value" id="ref-for-inherited-value①">inherited value</a>. <h4 class="heading settled caniuse-paneled" data-level="7.3.3" id="inherit-initial">7.3.3. Erasing All Declarations: the <a class="css" data-link-type="maybe" href="#valdef-all-unset" id="ref-for-valdef-all-unset">unset</a> keyword<a class="self-link" href="#inherit-initial"></a></h4> The <dfn class="dfn-paneled css" data-dfn-for="all" data-dfn-type="value" data-export id="valdef-all-unset">unset</dfn> <a data-link-type="dfn" href="https://drafts.csswg.org/css-values-3/#css-wide-keywords" id="ref-for-css-wide-keywords③">CSS-wide keyword</a> acts as either <a class="css" data-link-type="maybe" href="#valdef-all-inherit" id="ref-for-valdef-all-inherit④">inherit</a> or <a class="css" data-link-type="maybe" href="#valdef-all-initial" id="ref-for-valdef-all-initial③">initial</a>, depending on whether the property is <a data-link-type="dfn" href="#inherited-property" id="ref-for-inherited-property②">inherited</a> or not. If the <a data-link-type="dfn" href="#cascaded-value" id="ref-for-cascaded-value①⓪">cascaded value</a> of a property is the <a class="css" data-link-type="maybe" href="#valdef-all-unset" id="ref-for-valdef-all-unset①">unset</a> keyword, then if it is an inherited property, this is treated as <a class="css" data-link-type="maybe" href="#valdef-all-inherit" id="ref-for-valdef-all-inherit⑤">inherit</a>, and if it is not, this is treated as <a class="css" data-link-type="maybe" href="#valdef-all-initial" id="ref-for-valdef-all-initial④">initial</a>. This keyword effectively erases all <a data-link-type="dfn" href="#declared-value" id="ref-for-declared-value⑦">declared values</a> occurring earlier in the <a data-link-type="dfn" href="#cascade" id="ref-for-cascade⑧">cascade</a>, correctly inheriting or not as appropriate for the property (or all longhands of a <a data-link-type="dfn" href="#shorthand-property" id="ref-for-shorthand-property①①">shorthand</a>). <h2 class="heading settled" data-level="8" id="changes">8. Changes<a class="self-link" href="#changes"></a></h2> See also <a href="https://www.w3.org/TR/2021/REC-css-cascade-3-20210211/#changes">Changes prior to reaching Recommendation</a>. <h3 class="heading settled" data-level="8.1" id="changes-2018">8.1. Changes Since the 11 February 2021 Recommendation<a class="self-link" href="#changes-2018"></a></h3> Non-trivial changes since the <a href="https://www.w3.org/TR/2021/REC-css-cascade-3-20210211/#changes">11 February 2021 Recommendation</a> include: <ul class="non-normative"> <li id="change-2020-properties"><a class="self-link" href="#change-2020-properties"></a> Added a paragraph to the introduction to define the term <a data-link-type="dfn">property</a>. (<a href="https://github.com/w3c/csswg-drafts/issues/5633">Issue 5633</a>) </ul> <h3 class="heading settled" data-level="8.2" id="changes-2">8.2. Additions Since Level 2<a class="self-link" href="#changes-2"></a></h3> The following features have been added since <a href="http://www.w3.org/TR/CSS2/cascade.html">Level 2</a>: <ul> <li>The <a class="property css" data-link-type="property" href="#propdef-all" id="ref-for-propdef-all③">all</a> shorthand <li>The <a class="css" data-link-type="maybe" href="#valdef-all-initial" id="ref-for-valdef-all-initial⑤">initial</a> keyword <li>The <a class="css" data-link-type="maybe" href="#valdef-all-unset" id="ref-for-valdef-all-unset②">unset</a> keyword <li>Incorporation of animations and transitions into the <a data-link-type="dfn" href="#cascade" id="ref-for-cascade⑨">cascade</a>. </ul> <h2 class="no-num heading settled" id="acknowledgments">Acknowledgments<a class="self-link" href="#acknowledgments"></a></h2> David Baron, Simon Sapin, and Boris Zbarsky contributed to this specification. <h2 class="no-num heading settled" id="priv-sec"> Privacy and Security Considerations<a class="self-link" href="#priv-sec"></a></h2> <ul> <li data-md> The cascade process does not distinguish between same-origin and cross-origin stylesheets, enabling the content of cross-origin stylesheets to be inferred from the computed styles they apply to a document. <li data-md> User preferences and UA defaults expressed via application of style rules are exposed by the cascade process, and can be inferred from the computed styles they apply to a document. <li data-md> The <a class="css" data-link-type="maybe" href="#at-ruledef-import" id="ref-for-at-ruledef-import①③">@import</a> rule does not apply the <a data-link-type="dfn" href="https://fetch.spec.whatwg.org/#cors-protocol" id="ref-for-cors-protocol">CORS protocol</a> to loading cross-origin stylesheets, instead allowing them to be freely imported and applied. <li data-md> The <a class="css" data-link-type="maybe" href="#at-ruledef-import" id="ref-for-at-ruledef-import①④">@import</a> rule assumes that resources without <a href="https://html.spec.whatwg.org/multipage/urls-and-fetching.html#content-type"><code>Content-Type</code> metadata</a> (or any same-origin file if the host document is in quirks mode) are <code>text/css</code>, potentially allowing arbitrary files to be imported into the page and interpreted as CSS, potentially allowing sensitive data to be inferred from the computed styles they apply to a document. </ul> </main> <h2 class="no-ref no-num heading settled" id="w3c-conformance"> Conformance<a class="self-link" href="#w3c-conformance"></a></h2> <h3 class="no-ref heading settled" id="w3c-conventions"> Document conventions<a class="self-link" href="#w3c-conventions"></a></h3> Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology. The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this document are to be interpreted as described in RFC 2119. However, for readability, these words do not appear in all uppercase letters in this specification. All of the text of this specification is normative except sections explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119" title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</a> Examples in this specification are introduced with the words “for example” or are set apart from the normative text with <code>class="example"</code>, like this: <div class="example" id="w3c-example"> <a class="self-link" href="#w3c-example"></a> This is an example of an informative example. </div> Informative notes begin with the word “Note” and are set apart from the normative text with <code>class="note"</code>, like this: Note, this is an informative note. Advisements are normative sections styled to evoke special attention and are set apart from other normative text with <code></code>, like this: UAs MUST provide an accessible alternative. <details class="wpt-tests-block" dir="ltr" lang="en" open> <summary>Tests</summary> Tests relating to the content of this specification may be documented in “Tests” blocks like this one. Any such block is non-normative. <ul class="wpt-tests-list"></ul> <hr> </details> <h3 class="no-ref heading settled" id="w3c-conformance-classes"> Conformance classes<a class="self-link" href="#w3c-conformance-classes"></a></h3> Conformance to this specification is defined for three conformance classes: <dl> <dt>style sheet <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS style sheet</a>. <dt>renderer <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a> that interprets the semantics of a style sheet and renders documents that use them. <dt>authoring tool <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a> that writes a style sheet. </dl> A style sheet is conformant to this specification if all of its statements that use syntax defined in this module are valid according to the generic CSS grammar and the individual grammars of each feature defined in this module. A renderer is conformant to this specification if, in addition to interpreting the style sheet as defined by the appropriate specifications, it supports all the features defined by this specification by parsing them correctly and rendering the document accordingly. However, the inability of a UA to correctly render a document due to limitations of the device does not make the UA non-conformant. (For example, a UA is not required to render color on a monochrome monitor.) An authoring tool is conformant to this specification if it writes style sheets that are syntactically correct according to the generic CSS grammar and the individual grammars of each feature in this module, and meet all other conformance requirements of style sheets as described in this module. <h3 class="no-ref heading settled" id="w3c-partial"> Partial implementations<a class="self-link" href="#w3c-partial"></a></h3> So that authors can exploit the forward-compatible parsing rules to assign fallback values, CSS renderers must treat as invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore as appropriate</a>) any at-rules, properties, property values, keywords, and other syntactic constructs for which they have no usable level of support. In particular, user agents must not selectively ignore unsupported component values and honor supported values in a single multi-value property declaration: if any value is considered invalid (as unsupported values must be), CSS requires that the entire declaration be ignored. <h4 class="heading settled" id="w3c-conform-future-proofing"> Implementations of Unstable and Proprietary Features<a class="self-link" href="#w3c-conform-future-proofing"></a></h4> To avoid clashes with future stable CSS features, the CSSWG recommends <a href="http://www.w3.org/TR/CSS/#future-proofing">following best practices</a> for the implementation of <a href="http://www.w3.org/TR/CSS/#unstable">unstable</a> features and <a href="http://www.w3.org/TR/CSS/#proprietary-extension">proprietary extensions</a> to CSS. <h3 class="no-ref heading settled" id="w3c-testing"> Non-experimental implementations<a class="self-link" href="#w3c-testing"></a></h3> Once a specification reaches the Candidate Recommendation stage, non-experimental implementations are possible, and implementors should release an unprefixed implementation of any CR-level feature they can demonstrate to be correctly implemented according to spec. To establish and maintain the interoperability of CSS across implementations, the CSS Working Group requests that non-experimental CSS renderers submit an implementation report (and, if necessary, the testcases used for that implementation report) to the W3C before releasing an unprefixed implementation of any CSS features. Testcases submitted to W3C are subject to review and correction by the CSS Working Group. Further information on submitting testcases and implementation reports can be found from on the CSS Working Group’s website at <a href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>. Questions should be directed to the <a href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a> mailing list. <script src="https://www.w3.org/scripts/TR/2021/fixup.js"></script> <h2 class="no-num no-ref heading settled" id="index">Index<a class="self-link" href="#index"></a></h2> <h3 class="no-num no-ref heading settled" id="index-defined-here">Terms defined by this specification<a class="self-link" href="#index-defined-here"></a></h3> <ul class="index"> <li><a href="#actual-value">actual</a>, in § 4.6 <li><a href="#actual-value">actual value</a>, in § 4.6 <li><a href="#propdef-all">all</a>, in § 3.1 <li><a href="#cascade-origin-animation">Animation Origin</a>, in § 6.2 <li><a href="#applies-to">applies to</a>, in § 4.5 <li><a href="#applies-to">apply to</a>, in § 4.5 <li><a href="#cascade-origin-author">author origin</a>, in § 6.2 <li><a href="#cascade-origin-author">author-origin</a>, in § 6.2 <li><a href="#cascade-origin-author">author style sheet</a>, in § 6.2 <li><a href="#cascade">cascade</a>, in § 6 <li><a href="#cascaded-value">cascaded</a>, in § 4.2 <li><a href="#cascaded-value">cascaded value</a>, in § 4.2 <li><a href="#origin">cascade origin</a>, in § 6.2 <li><a href="#computed-value">computed</a>, in § 4.4 <li><a href="#computed-value">computed value</a>, in § 4.4 <li><a href="#declared-value">declared</a>, in § 4.1 <li><a href="#declared-value">declared value</a>, in § 4.1 <li><a href="#at-ruledef-import">@import</a>, in § 2 <li><a href="#important">importance</a>, in § 6.3 <li><a href="#important">important</a>, in § 6.3 <li><a href="#import-conditions">import conditions</a>, in § 2 <li> inherit <ul> <li><a href="#css-inheritance">dfn for CSS</a>, in § 7.2 <li><a href="#valdef-all-inherit">value for all</a>, in § 7.3.2 </ul> <li><a href="#css-inheritance">inheritance</a>, in § 7.2 <li><a href="#inherited-property">inherited property</a>, in § 7.2 <li><a href="#inherited-value">inherited value</a>, in § 7.2 <li><a href="#valdef-all-initial">initial</a>, in § 7.3.1 <li><a href="#initial-value">initial value</a>, in § 7.1 <li><a href="#longhand">longhand</a>, in § 3 <li><a href="#longhand">longhand property</a>, in § 3 <li><a href="#normal">normal</a>, in § 6.3 <li><a href="#origin">origin</a>, in § 6.2 <li><a href="#output-of-the-cascade">output of the cascade</a>, in § 6.1 <li><a href="#css-property">property</a>, in § 1 <li><a href="#reset-only-sub-property">reset-only sub-property</a>, in § 3 <li><a href="#shorthand-property">shorthand</a>, in § 3 <li><a href="#shorthand-property">shorthand property</a>, in § 3 <li><a href="#specified-value">specified</a>, in § 4.3 <li><a href="#specified-value">specified value</a>, in § 4.3 <li><a href="#longhand">sub-property</a>, in § 3 <li><a href="#cascade-origin-transition">Transition Origin</a>, in § 6.2 <li><a href="#cascade-origin-ua">UA origin</a>, in § 6.2 <li><a href="#cascade-origin-ua">UA-origin</a>, in § 6.2 <li><a href="#cascade-origin-ua">UA style sheet</a>, in § 6.2 <li><a href="#valdef-all-unset">unset</a>, in § 7.3.3 <li><a href="#used-value">used</a>, in § 4.5 <li><a href="#used-value">used value</a>, in § 4.5 <li><a href="#cascade-origin-ua">user-agent origin</a>, in § 6.2 <li><a href="#cascade-origin-ua">user-agent style sheet</a>, in § 6.2 <li><a href="#cascade-origin-user">user origin</a>, in § 6.2 <li><a href="#cascade-origin-user">user-origin</a>, in § 6.2 <li><a href="#cascade-origin-user">user style sheet</a>, in § 6.2 </ul> <h3 class="no-num no-ref heading settled" id="index-defined-elsewhere">Terms defined by reference<a class="self-link" href="#index-defined-elsewhere"></a></h3> <ul class="index"> <li> <a data-link-type="biblio">[CSS-ALIGN-3]</a> defines the following terms: <ul> <li>auto </ul> <li> <a data-link-type="biblio">[CSS-BACKGROUNDS-3]</a> defines the following terms: <ul> <li>background <li>background-color <li>background-image <li>border <li>border-bottom-width <li>border-image <li>border-left-width <li>border-right-width <li>border-style <li>border-top-width <li>dotted </ul> <li> <a data-link-type="biblio">[CSS-BREAK-3]</a> defines the following terms: <ul> <li>break-before <li>orphans </ul> <li> <a data-link-type="biblio">[CSS-BREAK-4]</a> defines the following terms: <ul> <li>page </ul> <li> <a data-link-type="biblio">[CSS-COLOR-4]</a> defines the following terms: <ul> <li>color </ul> <li> <a data-link-type="biblio">[CSS-COLOR-5]</a> defines the following terms: <ul> <li><color> </ul> <li> <a data-link-type="biblio">[CSS-CONDITIONAL-3]</a> defines the following terms: <ul> <li>@media </ul> <li> <a data-link-type="biblio">[CSS-DISPLAY-4]</a> defines the following terms: <ul> <li>display type </ul> <li> <a data-link-type="biblio">[CSS-FLEXBOX-1]</a> defines the following terms: <ul> <li>flex <li>flex item </ul> <li> <a data-link-type="biblio">[CSS-FONTS-5]</a> defines the following terms: <ul> <li>font-size-adjust </ul> <li> <a data-link-type="biblio">[CSS-LISTS-3]</a> defines the following terms: <ul> <li>list-style-position </ul> <li> <a data-link-type="biblio">[CSS-NAMESPACES-3]</a> defines the following terms: <ul> <li>@namespace </ul> <li> <a data-link-type="biblio">[CSS-PSEUDO-4]</a> defines the following terms: <ul> <li>::after <li>::before </ul> <li> <a data-link-type="biblio">[CSS-SIZING-3]</a> defines the following terms: <ul> <li>height <li>width </ul> <li> <a data-link-type="biblio">[CSS-SYNTAX-3]</a> defines the following terms: <ul> <li>@charset <li>declaration <li>environment encoding <li>property declarations </ul> <li> <a data-link-type="biblio">[CSS-TEXT-3]</a> defines the following terms: <ul> <li>text-align </ul> <li> <a data-link-type="biblio">[CSS-TEXT-4]</a> defines the following terms: <ul> <li>text-indent </ul> <li> <a data-link-type="biblio">[CSS-VALUES-3]</a> defines the following terms: <ul> <li><length-percentage> <li>? <li>CSS-wide keywords <li>em <li>ex <li>url() <li>vh <li>vw <li>| </ul> <li> <a data-link-type="biblio">[CSS-VALUES-4]</a> defines the following terms: <ul> <li><string> <li><url> </ul> <li> <a data-link-type="biblio">[CSS-VARIABLES-2]</a> defines the following terms: <ul> <li>custom property </ul> <li> <a data-link-type="biblio">[CSS-VIEWPORT-1]</a> defines the following terms: <ul> <li>zoom </ul> <li> <a data-link-type="biblio">[CSS-WRITING-MODES-3]</a> defines the following terms: <ul> <li>direction <li>unicode-bidi </ul> <li> <a data-link-type="biblio">[CSS2]</a> defines the following terms: <ul> <li>display <li>page-break-after <li>pseudo-elements <li>red </ul> <li> <a data-link-type="biblio">[CSSOM]</a> defines the following terms: <ul> <li>declarations <li>getComputedStyle(elt) </ul> <li> <a data-link-type="biblio">[FETCH]</a> defines the following terms: <ul> <li>CORS protocol </ul> <li> <a data-link-type="biblio">[HTML]</a> defines the following terms: <ul> <li>s </ul> <li> <a data-link-type="biblio">[MEDIAQ]</a> defines the following terms: <ul> <li><media-query-list> <li><media-query> </ul> <li> <a data-link-type="biblio">[SELECTORS-4]</a> defines the following terms: <ul> <li>pseudo-element </ul> </ul> <h2 class="no-num no-ref heading settled" id="references">References<a class="self-link" href="#references"></a></h2> <h3 class="no-num no-ref heading settled" id="normative">Normative References<a class="self-link" href="#normative"></a></h3> <dl> <dt id="biblio-css-animations-1">[CSS-ANIMATIONS-1] <dd>David Baron; et al. <a href="https://drafts.csswg.org/css-animations/"><cite>CSS Animations Level 1</cite></a>. URL: <a href="https://drafts.csswg.org/css-animations/">https://drafts.csswg.org/css-animations/</a> <dt id="biblio-css-backgrounds-3">[CSS-BACKGROUNDS-3] <dd>Elika Etemad; Brad Kemper. <a href="https://drafts.csswg.org/css-backgrounds/"><cite>CSS Backgrounds and Borders Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-backgrounds/">https://drafts.csswg.org/css-backgrounds/</a> <dt id="biblio-css-color-4">[CSS-COLOR-4] <dd>Chris Lilley; Tab Atkins Jr.; Lea Verou. <a href="https://drafts.csswg.org/css-color-4/"><cite>CSS Color Module Level 4</cite></a>. URL: <a href="https://drafts.csswg.org/css-color-4/">https://drafts.csswg.org/css-color-4/</a> <dt id="biblio-css-color-5">[CSS-COLOR-5] <dd>Chris Lilley; et al. <a href="https://drafts.csswg.org/css-color-5/"><cite>CSS Color Module Level 5</cite></a>. URL: <a href="https://drafts.csswg.org/css-color-5/">https://drafts.csswg.org/css-color-5/</a> <dt id="biblio-css-conditional-3">[CSS-CONDITIONAL-3] <dd>Chris Lilley; David Baron; Elika Etemad. <a href="https://drafts.csswg.org/css-conditional-3/"><cite>CSS Conditional Rules Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-conditional-3/">https://drafts.csswg.org/css-conditional-3/</a> <dt id="biblio-css-namespaces-3">[CSS-NAMESPACES-3] <dd>Elika Etemad. <a href="https://drafts.csswg.org/css-namespaces/"><cite>CSS Namespaces Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-namespaces/">https://drafts.csswg.org/css-namespaces/</a> <dt id="biblio-css-syntax-3">[CSS-SYNTAX-3] <dd>Tab Atkins Jr.; Simon Sapin. <a href="https://drafts.csswg.org/css-syntax/"><cite>CSS Syntax Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-syntax/">https://drafts.csswg.org/css-syntax/</a> <dt id="biblio-css-transitions-1">[CSS-TRANSITIONS-1] <dd>David Baron; et al. <a href="https://drafts.csswg.org/css-transitions/"><cite>CSS Transitions</cite></a>. URL: <a href="https://drafts.csswg.org/css-transitions/">https://drafts.csswg.org/css-transitions/</a> <dt id="biblio-css-values-3">[CSS-VALUES-3] <dd>Tab Atkins Jr.; Elika Etemad. <a href="https://drafts.csswg.org/css-values-3/"><cite>CSS Values and Units Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-values-3/">https://drafts.csswg.org/css-values-3/</a> <dt id="biblio-css-values-4">[CSS-VALUES-4] <dd>Tab Atkins Jr.; Elika Etemad. <a href="https://drafts.csswg.org/css-values-4/"><cite>CSS Values and Units Module Level 4</cite></a>. URL: <a href="https://drafts.csswg.org/css-values-4/">https://drafts.csswg.org/css-values-4/</a> <dt id="biblio-css-variables-2">[CSS-VARIABLES-2] <dd><a href="https://drafts.csswg.org/css-variables-2/"><cite>CSS Custom Properties for Cascading Variables Module Level 2</cite></a>. Editor's Draft. URL: <a href="https://drafts.csswg.org/css-variables-2/">https://drafts.csswg.org/css-variables-2/</a> <dt id="biblio-css-viewport-1">[CSS-VIEWPORT-1] <dd>Florian Rivoal; Emilio Cobos Álvarez. <a href="https://drafts.csswg.org/css-viewport/"><cite>CSS Viewport Module Level 1</cite></a>. URL: <a href="https://drafts.csswg.org/css-viewport/">https://drafts.csswg.org/css-viewport/</a> <dt id="biblio-css-writing-modes-3">[CSS-WRITING-MODES-3] <dd>Elika Etemad; Koji Ishii. <a href="https://drafts.csswg.org/css-writing-modes-3/"><cite>CSS Writing Modes Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-writing-modes-3/">https://drafts.csswg.org/css-writing-modes-3/</a> <dt id="biblio-css2">[CSS2] <dd>Bert Bos; et al. <a href="https://drafts.csswg.org/css2/"><cite>Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification</cite></a>. URL: <a href="https://drafts.csswg.org/css2/">https://drafts.csswg.org/css2/</a> <dt id="biblio-cssom">[CSSOM] <dd>Daniel Glazman; Emilio Cobos Álvarez. <a href="https://drafts.csswg.org/cssom/"><cite>CSS Object Model (CSSOM)</cite></a>. URL: <a href="https://drafts.csswg.org/cssom/">https://drafts.csswg.org/cssom/</a> <dt id="biblio-cssstyleattr">[CSSSTYLEATTR] <dd>Tantek Çelik; Elika Etemad. <a href="https://drafts.csswg.org/css-style-attr/"><cite>CSS Style Attributes</cite></a>. URL: <a href="https://drafts.csswg.org/css-style-attr/">https://drafts.csswg.org/css-style-attr/</a> <dt id="biblio-fetch">[FETCH] <dd>Anne van Kesteren. <a href="https://fetch.spec.whatwg.org/"><cite>Fetch Standard</cite></a>. Living Standard. URL: <a href="https://fetch.spec.whatwg.org/">https://fetch.spec.whatwg.org/</a> <dt id="biblio-html">[HTML] <dd>Anne van Kesteren; et al. <a href="https://html.spec.whatwg.org/multipage/"><cite>HTML Standard</cite></a>. Living Standard. URL: <a href="https://html.spec.whatwg.org/multipage/">https://html.spec.whatwg.org/multipage/</a> <dt id="biblio-mediaq">[MEDIAQ] <dd>Florian Rivoal; Tab Atkins Jr.. <a href="https://drafts.csswg.org/mediaqueries-4/"><cite>Media Queries Level 4</cite></a>. URL: <a href="https://drafts.csswg.org/mediaqueries-4/">https://drafts.csswg.org/mediaqueries-4/</a> <dt id="biblio-rfc2119">[RFC2119] <dd>S. Bradner. <a href="https://datatracker.ietf.org/doc/html/rfc2119"><cite>Key words for use in RFCs to Indicate Requirement Levels</cite></a>. March 1997. Best Current Practice. URL: <a href="https://datatracker.ietf.org/doc/html/rfc2119">https://datatracker.ietf.org/doc/html/rfc2119</a> <dt id="biblio-select">[SELECT] <dd>Tantek Çelik; et al. <a href="https://drafts.csswg.org/selectors-3/"><cite>Selectors Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/selectors-3/">https://drafts.csswg.org/selectors-3/</a> <dt id="biblio-selectors-4">[SELECTORS-4] <dd>Elika Etemad; Tab Atkins Jr.. <a href="https://drafts.csswg.org/selectors/"><cite>Selectors Level 4</cite></a>. URL: <a href="https://drafts.csswg.org/selectors/">https://drafts.csswg.org/selectors/</a> </dl> <h3 class="no-num no-ref heading settled" id="informative">Informative References<a class="self-link" href="#informative"></a></h3> <dl> <dt id="biblio-css-align-3">[CSS-ALIGN-3] <dd>Elika Etemad; Tab Atkins Jr.. <a href="https://drafts.csswg.org/css-align/"><cite>CSS Box Alignment Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-align/">https://drafts.csswg.org/css-align/</a> <dt id="biblio-css-break-3">[CSS-BREAK-3] <dd>Rossen Atanassov; Elika Etemad. <a href="https://drafts.csswg.org/css-break/"><cite>CSS Fragmentation Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-break/">https://drafts.csswg.org/css-break/</a> <dt id="biblio-css-break-4">[CSS-BREAK-4] <dd>Rossen Atanassov; Elika Etemad. <a href="https://drafts.csswg.org/css-break-4/"><cite>CSS Fragmentation Module Level 4</cite></a>. URL: <a href="https://drafts.csswg.org/css-break-4/">https://drafts.csswg.org/css-break-4/</a> <dt id="biblio-css-display-4">[CSS-DISPLAY-4] <dd>Elika Etemad; Tab Atkins Jr.. <a href="https://drafts.csswg.org/css-display/"><cite>CSS Display Module Level 4</cite></a>. URL: <a href="https://drafts.csswg.org/css-display/">https://drafts.csswg.org/css-display/</a> <dt id="biblio-css-flexbox-1">[CSS-FLEXBOX-1] <dd>Tab Atkins Jr.; et al. <a href="https://drafts.csswg.org/css-flexbox-1/"><cite>CSS Flexible Box Layout Module Level 1</cite></a>. URL: <a href="https://drafts.csswg.org/css-flexbox-1/">https://drafts.csswg.org/css-flexbox-1/</a> <dt id="biblio-css-fonts-5">[CSS-FONTS-5] <dd>Chris Lilley. <a href="https://drafts.csswg.org/css-fonts-5/"><cite>CSS Fonts Module Level 5</cite></a>. URL: <a href="https://drafts.csswg.org/css-fonts-5/">https://drafts.csswg.org/css-fonts-5/</a> <dt id="biblio-css-lists-3">[CSS-LISTS-3] <dd>Elika Etemad; Tab Atkins Jr.. <a href="https://drafts.csswg.org/css-lists-3/"><cite>CSS Lists and Counters Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-lists-3/">https://drafts.csswg.org/css-lists-3/</a> <dt id="biblio-css-page-3">[CSS-PAGE-3] <dd>Elika Etemad. <a href="https://drafts.csswg.org/css-page-3/"><cite>CSS Paged Media Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-page-3/">https://drafts.csswg.org/css-page-3/</a> <dt id="biblio-css-pseudo-4">[CSS-PSEUDO-4] <dd>Daniel Glazman; Elika Etemad; Alan Stearns. <a href="https://drafts.csswg.org/css-pseudo-4/"><cite>CSS Pseudo-Elements Module Level 4</cite></a>. URL: <a href="https://drafts.csswg.org/css-pseudo-4/">https://drafts.csswg.org/css-pseudo-4/</a> <dt id="biblio-css-sizing-3">[CSS-SIZING-3] <dd>Tab Atkins Jr.; Elika Etemad. <a href="https://drafts.csswg.org/css-sizing-3/"><cite>CSS Box Sizing Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-sizing-3/">https://drafts.csswg.org/css-sizing-3/</a> <dt id="biblio-css-text-3">[CSS-TEXT-3] <dd>Elika Etemad; Koji Ishii; Florian Rivoal. <a href="https://drafts.csswg.org/css-text-3/"><cite>CSS Text Module Level 3</cite></a>. URL: <a href="https://drafts.csswg.org/css-text-3/">https://drafts.csswg.org/css-text-3/</a> <dt id="biblio-css-text-4">[CSS-TEXT-4] <dd>Elika Etemad; et al. <a href="https://drafts.csswg.org/css-text-4/"><cite>CSS Text Module Level 4</cite></a>. URL: <a href="https://drafts.csswg.org/css-text-4/">https://drafts.csswg.org/css-text-4/</a> <dt id="biblio-css-variables-1">[CSS-VARIABLES-1] <dd>Tab Atkins Jr.. <a href="https://drafts.csswg.org/css-variables/"><cite>CSS Custom Properties for Cascading Variables Module Level 1</cite></a>. URL: <a href="https://drafts.csswg.org/css-variables/">https://drafts.csswg.org/css-variables/</a> <dt id="biblio-svg11">[SVG11] <dd>Erik Dahlström; et al. <a href="https://www.w3.org/TR/SVG11/"><cite>Scalable Vector Graphics (SVG) 1.1 (Second Edition)</cite></a>. 16 August 2011. REC. URL: <a href="https://www.w3.org/TR/SVG11/">https://www.w3.org/TR/SVG11/</a> </dl> <h2 class="no-num no-ref heading settled" id="property-index">Property Index<a class="self-link" href="#property-index"></a></h2> <div class="big-element-wrapper"> <table class="index"> <thead> <tr> <th scope="col">Name <th scope="col">Value <th scope="col">Initial <th scope="col">Applies to <th scope="col">Inh. <th scope="col">%ages <th scope="col">Animation type <th scope="col">Canonical order <th scope="col">Computed value <tbody> <tr> <th scope="row"><a class="css" data-link-type="property" href="#propdef-all" id="ref-for-propdef-all④">all</a> <td>initial | inherit | unset <td>see individual properties <td>see individual properties <td>see individual properties <td>see individual properties <td>see individual properties <td>per grammar <td>see individual properties </table> </div> <details class="mdn-anno unpositioned" data-anno-for="all-shorthand"> <summary>✔MDN</summary> <div class="feature"> <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/all" title="The all shorthand CSS property resets all of an element's properties except unicode-bidi, direction, and CSS Custom Properties. It can set properties to their initial or inherited values, or to the values specified in another cascade layer or stylesheet origin.">all</a> In all current engines. <div class="support"> Firefox27+Safari9.1+Chrome37+ <hr> Opera?Edge79+ <hr> Edge (Legacy)?IENone <hr> Firefox for Android?iOS Safari?Chrome for Android?Android WebView?Samsung Internet?Opera Mobile? </div> </div> </details> <details class="mdn-anno unpositioned" data-anno-for="inherit"> <summary>✔MDN</summary> <div class="feature"> <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/inherit" title="The inherit CSS keyword causes the element to take the computed value of the property from its parent element. It can be applied to any CSS property, including the CSS shorthand property all.">inherit</a> In all current engines. <div class="support"> Firefox1+Safari1+Chrome1+ <hr> Opera4+Edge79+ <hr> Edge (Legacy)12+IE8+ <hr> Firefox for Android?iOS Safari?Chrome for Android?Android WebView?Samsung Internet?Opera Mobile? </div> </div> </details> <details class="mdn-anno unpositioned" data-anno-for="initial"> <summary>✔MDN</summary> <div class="feature"> <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/initial" title="The initial CSS keyword applies the initial (or default) value of a property to an element. It can be applied to any CSS property, including the CSS shorthand property all. With all set to initial, all CSS properties can be restored to their respective initial values in one go instead of restoring each one separately.">initial</a> In all current engines. <div class="support"> Firefox19+Safari1.2+Chrome1+ <hr> Opera?Edge79+ <hr> Edge (Legacy)13+IENone <hr> Firefox for Android?iOS Safari?Chrome for Android?Android WebView?Samsung Internet?Opera Mobile? </div> </div> </details> <details class="mdn-anno unpositioned" data-anno-for="inherit-initial"> <summary>✔MDN</summary> <div class="feature"> <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/unset" title="The unset CSS keyword resets a property to its inherited value if the property naturally inherits from its parent, and to its initial value if not. In other words, it behaves like the inherit keyword in the first case, when the property is an inherited property, and like the initial keyword in the second case, when the property is a non-inherited property.">unset</a> In all current engines. <div class="support"> Firefox27+Safari9.1+Chrome41+ <hr> Opera?Edge79+ <hr> Edge (Legacy)13+IENone <hr> Firefox for Android?iOS Safari?Chrome for Android?Android WebView?Samsung Internet?Opera Mobile? </div> </div> </details> <details class="caniuse-status unpositioned" data-anno-for="all-shorthand" data-deco> <summary>CanIUse</summary> Support:Android Browser4.4.3+Baidu Browser13.52+Blackberry BrowserNoneChrome37+Chrome for Android132+Edge79+Firefox27+Firefox for Android132+IENoneIE MobileNoneKaiOS Browser2.5+Opera24+Opera MiniNoneOpera Mobile80+QQ Browser14.9+Safari9.1+Safari on iOS9.3+Samsung Internet4+UC Browser for Android15.5+ Source: <a href="https://caniuse.com/#feat=css-all">caniuse.com</a> as of 2025-02-16 </details> <details class="caniuse-status unpositioned" data-anno-for="initial" data-deco> <summary>CanIUse</summary> Support:Android Browser2.3+Baidu Browser13.52+Blackberry Browser7+Chrome4+Chrome for Android132+Edge12+Firefox19+Firefox for Android132+IENoneIE MobileNoneKaiOS Browser2.5+Opera15+Opera MiniNoneOpera Mobile80+QQ Browser14.9+Safari3.2+Safari on iOS4.0+Samsung Internet4+UC Browser for Android15.5+ Source: <a href="https://caniuse.com/#feat=css-initial-value">caniuse.com</a> as of 2025-02-16 </details> <details class="caniuse-status unpositioned" data-anno-for="inherit-initial" data-deco> <summary>CanIUse</summary> Support:Android Browser132+Baidu Browser13.52+Blackberry BrowserNoneChrome41+Chrome for Android132+Edge13+Firefox27+Firefox for Android132+IENoneIE MobileNoneKaiOS Browser2.5+Opera28+Opera MiniNoneOpera Mobile80+QQ Browser14.9+Safari9.1+Safari on iOS9.3+Samsung Internet4+UC Browser for Android15.5+ Source: <a href="https://caniuse.com/#feat=css-unset-value">caniuse.com</a> as of 2025-02-16 </details> <script>/* Boilerplate: script-dom-helper */ "use strict"; function query(sel) { return document.querySelector(sel); } function queryAll(sel) { return [...document.querySelectorAll(sel)]; } function iter(obj) { if(!obj) return []; var it = obj[Symbol.iterator]; if(it) return it; return Object.entries(obj); } function mk(tagname, attrs, ...children) { const el = document.createElement(tagname); for(const [k,v] of iter(attrs)) { if(k.slice(0,3) == "_on") { const eventName = k.slice(3); el.addEventListener(eventName, v); } else if(k[0] == "_") { // property, not attribute el[k.slice(1)] = v; } else { if(v === false || v == null) { continue; } else if(v === true) { el.setAttribute(k, ""); continue; } else { el.setAttribute(k, v); } } } append(el, children); return el; } /* Create shortcuts for every known HTML element */ [ "a", "abbr", "acronym", "address", "applet", "area", "article", "aside", "audio", "b", "base", "basefont", "bdo", "big", "blockquote", "body", 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cascade","external":false,"refSections":[{"refs":[{"id":"ref-for-output-of-the-cascade"},{"id":"ref-for-output-of-the-cascade\u2460"}],"title":"4.2. \nCascaded Values"}],"url":"#output-of-the-cascade"}, "propdef-all": {"dfnID":"propdef-all","dfnText":"all","external":false,"refSections":[{"refs":[{"id":"ref-for-propdef-all"},{"id":"ref-for-propdef-all\u2460"},{"id":"ref-for-propdef-all\u2461"}],"title":"3.1. \nResetting All Properties: the all property"},{"refs":[{"id":"ref-for-propdef-all\u2462"}],"title":"8.2. \nAdditions Since Level 2"}],"url":"#propdef-all"}, "reset-only-sub-property": {"dfnID":"reset-only-sub-property","dfnText":"reset-only sub-property","external":false,"refSections":[{"refs":[{"id":"ref-for-reset-only-sub-property"}],"title":"3. \nShorthand Properties"}],"url":"#reset-only-sub-property"}, "shorthand-property": {"dfnID":"shorthand-property","dfnText":"shorthand properties","external":false,"refSections":[{"refs":[{"id":"ref-for-shorthand-property"},{"id":"ref-for-shorthand-property\u2460"},{"id":"ref-for-shorthand-property\u2461"},{"id":"ref-for-shorthand-property\u2462"},{"id":"ref-for-shorthand-property\u2463"},{"id":"ref-for-shorthand-property\u2464"},{"id":"ref-for-shorthand-property\u2465"},{"id":"ref-for-shorthand-property\u2466"},{"id":"ref-for-shorthand-property\u2467"}],"title":"3. \nShorthand Properties"},{"refs":[{"id":"ref-for-shorthand-property\u2468"}],"title":"3.1. \nResetting All Properties: the all property"},{"refs":[{"id":"ref-for-shorthand-property\u2460\u24ea"}],"title":"6.3. \nImportant Declarations: the !important annotation"},{"refs":[{"id":"ref-for-shorthand-property\u2460\u2460"}],"title":"7.3.3. \nErasing All Declarations: the unset keyword"}],"url":"#shorthand-property"}, "specified-value": {"dfnID":"specified-value","dfnText":"specified value","external":false,"refSections":[{"refs":[{"id":"ref-for-specified-value"}],"title":"1. \nIntroduction"},{"refs":[{"id":"ref-for-specified-value\u2460"},{"id":"ref-for-specified-value\u2461"}],"title":"4. \nValue Processing"},{"refs":[{"id":"ref-for-specified-value\u2462"},{"id":"ref-for-specified-value\u2463"},{"id":"ref-for-specified-value\u2464"},{"id":"ref-for-specified-value\u2465"}],"title":"4.3. \nSpecified Values"},{"refs":[{"id":"ref-for-specified-value\u2466"},{"id":"ref-for-specified-value\u2467"},{"id":"ref-for-specified-value\u2468"}],"title":"4.4. \nComputed Values"},{"refs":[{"id":"ref-for-specified-value\u2460\u24ea"}],"title":"7. \nDefaulting"},{"refs":[{"id":"ref-for-specified-value\u2460\u2460"}],"title":"7.1. \nInitial Values"},{"refs":[{"id":"ref-for-specified-value\u2460\u2461"}],"title":"7.3.1. \nResetting a Property: the initial keyword"},{"refs":[{"id":"ref-for-specified-value\u2460\u2462"}],"title":"7.3.2. \nExplicit Inheritance: the inherit 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{"dfnID":"valdef-all-unset","dfnText":"unset","external":false,"refSections":[{"refs":[{"id":"ref-for-valdef-all-unset"},{"id":"ref-for-valdef-all-unset\u2460"}],"title":"7.3.3. \nErasing All Declarations: the unset keyword"},{"refs":[{"id":"ref-for-valdef-all-unset\u2461"}],"title":"8.2. \nAdditions Since Level 2"}],"url":"#valdef-all-unset"}, }; document.addEventListener("DOMContentLoaded", ()=>{ genAllDfnPanels(); document.body.addEventListener("click", (e) => { // If not handled already, just hide all dfn panels. hideAllDfnPanels(); }); }); window.addEventListener("resize", () => { // Pin any visible dfn panel queryAll(".dfn-panel.on, .dfn-panel.activated").forEach(el=>positionDfnPanel(el)); }); function genAllDfnPanels() { for(const panelData of Object.values(dfnPanelData)) { const dfnID = panelData.dfnID; const dfn = document.getElementById(dfnID); if(!dfn) { console.log(`Can't find dfn#${dfnID}.`, panelData); continue; } dfn.panelData = panelData; insertDfnPopupAction(dfn); } } function genDfnPanel(dfn, { dfnID, url, dfnText, refSections, external }) { const dfnPanel = mk.aside({ class: "dfn-panel on", id: `infopanel-for-${dfnID}`, "data-for": dfnID, "aria-labelled-by":`infopaneltitle-for-${dfnID}`, }, mk.span({id:`infopaneltitle-for-${dfnID}`, style:"display:none"}, `Info about the '${dfnText}' ${external?"external":""} reference.`), mk.a({href:url, class:"dfn-link"}, url), refSections.length == 0 ? [] : mk.b({}, "Referenced in:"), mk.ul({}, ...refSections.map(section=> mk.li({}, ...section.refs.map((ref, refI)=> [ mk.a({ href: `#${ref.id}` }, (refI == 0) ? section.title : `(${refI + 1})` ), " ", ] ), ), ), ), genLinkingSyntaxes(dfn), ); dfnPanel.addEventListener('click', (event) => { if (event.target.nodeName == 'A') { scrollToTargetAndHighlight(event); pinDfnPanel(dfnPanel); } event.stopPropagation(); refocusOnTarget(event); }); dfnPanel.addEventListener('keydown', (event) => { if(event.keyCode == 27) { // Escape key hideDfnPanel({dfnPanel}); event.stopPropagation(); event.preventDefault(); } }); dfnPanel.dfn = dfn; dfn.dfnPanel = dfnPanel; return dfnPanel; } function hideAllDfnPanels() { // Delete the currently-active dfn panel. queryAll(".dfn-panel").forEach(dfnPanel=>hideDfnPanel({dfnPanel})); } function showDfnPanel(dfn) { hideAllDfnPanels(); // Only display one at a time. dfn.setAttribute("aria-expanded", "true"); const dfnPanel = genDfnPanel(dfn, dfn.panelData); // Give the dfn a unique tabindex, and then // give all the tabbable panel bits successive indexes. let tabIndex = 100; dfn.tabIndex = tabIndex++; const tabbable = dfnPanel.querySelectorAll(":is(a, button)"); for (const el of tabbable) { el.tabIndex = tabIndex++; } append(document.body, dfnPanel); positionDfnPanel(dfnPanel); } function positionDfnPanel(dfnPanel) { const dfn = dfnPanel.dfn; const dfnPos = getBounds(dfn); dfnPanel.style.top = dfnPos.bottom + "px"; dfnPanel.style.left = dfnPos.left + "px"; const panelPos = dfnPanel.getBoundingClientRect(); const panelMargin = 8; const maxRight = document.body.parentNode.clientWidth - panelMargin; if (panelPos.right > maxRight) { const overflowAmount = panelPos.right - maxRight; const newLeft = Math.max(panelMargin, dfnPos.left - overflowAmount); dfnPanel.style.left = newLeft + "px"; } } function pinDfnPanel(dfnPanel) { // Switch it to "activated" state, which pins it. dfnPanel.classList.add("activated"); dfnPanel.style.position = "fixed"; dfnPanel.style.left = null; dfnPanel.style.top = null; } function hideDfnPanel({dfn, dfnPanel}) { if(!dfnPanel) dfnPanel = dfn.dfnPanel; if(!dfn) dfn = dfnPanel.dfn; dfn.dfnPanel = undefined; dfnPanel.dfn = undefined; dfn.setAttribute("aria-expanded", "false"); dfn.tabIndex = undefined; dfnPanel.remove() } function toggleDfnPanel(dfn) { if(dfn.dfnPanel) { hideDfnPanel(dfn); } else { showDfnPanel(dfn); } } function insertDfnPopupAction(dfn) { dfn.setAttribute('role', 'button'); dfn.setAttribute('aria-expanded', 'false') dfn.tabIndex = 0; dfn.classList.add('has-dfn-panel'); dfn.addEventListener('click', (event) => { toggleDfnPanel(dfn); event.stopPropagation(); }); dfn.addEventListener('keypress', (event) => { const kc = event.keyCode; // 32->Space, 13->Enter if(kc == 32 || kc == 13) { toggleDfnPanel(dfn); event.stopPropagation(); event.preventDefault(); } }); } function refocusOnTarget(event) { const target = event.target; setTimeout(() => { // Refocus on the event.target element. // This is needed after browser scrolls to the destination. target.focus(); }); } // TODO: shared util // Returns the root-level absolute position {left and top} of element. function getBounds(el, relativeTo=document.body) { const relativeRect = relativeTo.getBoundingClientRect(); const elRect = el.getBoundingClientRect(); const top = elRect.top - relativeRect.top; const left = elRect.left - relativeRect.left; return { top, left, bottom: top + elRect.height, right: left + elRect.width, } } function scrollToTargetAndHighlight(event) { let hash = event.target.hash; if (hash) { hash = decodeURIComponent(hash.substring(1)); const dest = document.getElementById(hash); if (dest) { dest.classList.add('highlighted'); setTimeout(() => dest.classList.remove('highlighted'), 1000); } } } // Functions, divided by link type, that wrap an autolink's // contents with the appropriate outer syntax. // Alternately, a string naming another type they format // the same as. function needsFor(type) { switch(type) { case "descriptor": case "value": case "element-attr": case "attr-value": case "element-state": case "method": case "constructor": case "argument": case "attribute": case "const": case "dict-member": case "event": case "enum-value": case "stringifier": case "serializer": case "iterator": case "maplike": case "setlike": case "state": case "mode": case "context": case "facet": return true; default: return false; } } function refusesFor(type) { switch(type) { case "property": case "element": case "interface": case "namespace": case "callback": case "dictionary": case "enum": case "exception": case "typedef": case "http-header": case "permission": return true; default: return false; } } function linkFormatterFromType(type) { switch(type) { case 'scheme': case 'permission': case 'dfn': return (text) => `[=${text}=]`; case 'abstract-op': return (text) => `[\$${text}\$]`; case 'function': case 'at-rule': case 'selector': case 'value': return (text) => `''${text}''`; case 'http-header': return (text) => `[:${text}:]`; case 'interface': case 'constructor': case 'method': case 'argument': case 'attribute': case 'callback': case 'dictionary': case 'dict-member': case 'enum': case 'enum-value': case 'exception': case 'const': case 'typedef': case 'stringifier': case 'serializer': case 'iterator': case 'maplike': case 'setlike': case 'extended-attribute': case 'event': case 'idl': return (text) => `{{${text}}}`; case 'element-state': case 'element-attr': case 'attr-value': case 'element': return (element) => `<{${element}}>`; case 'grammar': return (text) => `${text} (within a <pre class=prod>)`; case 'type': return (text)=> `<<${text}>>`; case 'descriptor': case 'property': return (text) => `'${text}'`; default: return; }; }; function genLinkingSyntaxes(dfn) { if(dfn.tagName != "DFN") return; const type = dfn.getAttribute('data-dfn-type'); if(!type) { console.log(`<dfn> doesn't have a data-dfn-type:`, dfn); return []; } // Return a function that wraps link text based on the type const linkFormatter = linkFormatterFromType(type); if(!linkFormatter) { console.log(`<dfn> has an unknown data-dfn-type:`, dfn); return []; } let ltAlts; if(dfn.hasAttribute('data-lt')) { ltAlts = dfn.getAttribute('data-lt') .split("|") .map(x=>x.trim()); } else { ltAlts = [dfn.textContent.trim()]; } if(type == "type") { // lt of "<foo>", but "foo" is the interior; // <<foo/bar>> is how you write it with a for, // not <foo/<bar>> or whatever. for(var i = 0; i < ltAlts.length; i++) { const lt = ltAlts[i]; const match = /<(.*)>/.exec(lt); if(match) { ltAlts[i] = match[1]; } } } let forAlts; if(dfn.hasAttribute('data-dfn-for')) { forAlts = dfn.getAttribute('data-dfn-for') .split(",") .map(x=>x.trim()); } else { forAlts = ['']; } let linkingSyntaxes = []; if(!needsFor(type)) { for(const lt of ltAlts) { linkingSyntaxes.push(linkFormatter(lt)); } } if(!refusesFor(type)) { for(const f of forAlts) { linkingSyntaxes.push(linkFormatter(`${f}/${ltAlts[0]}`)) } } return [ mk.b({}, 'Possible linking syntaxes:'), mk.ul({}, ...linkingSyntaxes.map(link => { const copyLink = async () => await navigator.clipboard.writeText(link); return mk.li({}, mk.div({ class: 'link-item' }, mk.button({ class: 'copy-icon', title: 'Copy', type: 'button', _onclick: copyLink, tabindex: 0, }, mk.span({ class: 'icon' }) ), mk.span({}, link) ) ); }) ) ]; } } </script> <script>/* Boilerplate: script-link-titles */ "use strict"; { let linkTitleData = { "https://drafts.csswg.org/css-color-5/#typedef-color": "Expands to: <alpha-value> | aliceblue | antiquewhite | aqua | aquamarine | azure | beige | bisque | black | blanchedalmond | blue | blueviolet | brown | burlywood | cadetblue | chartreuse | chocolate | coral | cornflowerblue | cornsilk | crimson | currentcolor | cyan | darkblue | darkcyan | darkgoldenrod | darkgray | darkgreen | darkgrey | darkkhaki | darkmagenta | darkolivegreen | darkorange | darkorchid | darkred | darksalmon | darkseagreen | darkslateblue | darkslategray | darkslategrey | darkturquoise | darkviolet | deeppink | deepskyblue | dimgray | dimgrey | dodgerblue | firebrick | floralwhite | forestgreen | fuchsia | gainsboro | ghostwhite | gold | goldenrod | gray | green | greenyellow | grey | honeydew | hotpink | indianred | indigo | ivory | khaki | lavender | lavenderblush | lawngreen | lemonchiffon | lightblue | lightcoral | lightcyan | lightgoldenrodyellow | lightgray | lightgreen | lightgrey | lightpink | lightsalmon | lightseagreen | lightskyblue | lightslategray | lightslategrey | lightsteelblue | lightyellow | lime | limegreen | linen | magenta | maroon | mediumaquamarine | mediumblue | mediumorchid | mediumpurple | mediumseagreen | mediumslateblue | mediumspringgreen | mediumturquoise | mediumvioletred | midnightblue | mintcream | mistyrose | moccasin | navajowhite | navy | none | oldlace | olive | olivedrab | orange | orangered | orchid | palegoldenrod | palegreen | paleturquoise | palevioletred | papayawhip | peachpuff | peru | pink | plum | powderblue | purple | rebeccapurple | red | rosybrown | royalblue | saddlebrown | salmon | sandybrown | seagreen | seashell | sienna | silver | skyblue | slateblue | slategray | slategrey | snow | springgreen | steelblue | tan | teal | thistle | tomato | transparent | turquoise | violet | wheat | white | whitesmoke | yellow | yellowgreen", }; function setTypeTitles() { for(let el of document.querySelectorAll("a[href]")) { if(el.href in linkTitleData && !el.hasAttribute("title")) { el.setAttribute("title", linkTitleData[el.href]); } } } document.addEventListener("DOMContentLoaded", setTypeTitles); } </script> <script>/* Boilerplate: script-position-annos */ "use strict"; { function repositionAnnoPanels(){ const panels = [...document.querySelectorAll("[data-anno-for]")]; hydratePanels(panels); let vSoFar = 0; for(const panel of panels.sort(cmpTops)) { if(panel.top < vSoFar) { panel.top = vSoFar; panel.style.top = vSoFar + "px"; } vSoFar = panel.top + panel.height + 15; } } function hydratePanels(panels) { const main = document.querySelector("main"); let mainRect; if(main) mainRect = main.getBoundingClientRect(); // First display them all, if they're not already visible. for(const panel of panels) { panel.classList.remove("unpositioned"); } // Measure them all for(const panel of panels) { const dfn = document.getElementById(panel.getAttribute("data-anno-for")); if(!dfn) { console.log("Can't find the annotation panel target:", panel); continue; } panel.dfn = dfn; panel.top = window.scrollY + dfn.getBoundingClientRect().top; let panelRect = panel.getBoundingClientRect(); panel.height = panelRect.height; if(main) { panel.overlappingMain = panelRect.left < mainRect.right; } else { panel.overlappingMain = false; } } // And finally position them for(const panel of panels) { const dfn = panel.dfn; if(!dfn) continue; panel.style.top = panel.top + "px"; panel.classList.toggle("overlapping-main", panel.overlappingMain); } } function cmpTops(a,b) { return a.top - 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it's being displayed in a different way. // But allow casing differences, they're insignificant. dfnTextElements = mk.li({}, mk.b({}, "Term: "), mk.span({}, ref.displayText) ); } const forList = ref.for_; let forListElements; if(forList.length == 0) { forListElements = []; } else if(forList.length == 1) { forListElements = mk.li({}, mk.b({}, "For: "), mk.span({}, forList[0]), ); } else { forListElements = mk.li({}, mk.b({}, "For: "), mk.ul({}, ...forList.map(forItem => mk.li({}, mk.span({}, forItem) ), ), ), ); } const url = ref.url; const safeUrl = encodeURIComponent(url); const hintPanel = mk.aside({ class: "ref-hint", id: `ref-hint-for-${safeUrl}`, "data-for": url, "aria-labelled-by": `ref-hint-for-${safeUrl}`, }, mk.ul({}, dfnTextElements, mk.li({}, mk.b({}, "URL: "), mk.a({ href: url, class: "ref" }, url), ), mk.li({}, mk.b({}, "Type: "), mk.span({}, `${ref.type}`), ), mk.li({}, mk.b({}, "Spec: "), mk.span({}, `${ref.spec ? ref.spec : ''}`), ), forListElements ), ); hintPanel.forLink = link; setupRefHintEventListeners(link, hintPanel); return hintPanel; } function hideAllRefHints() { queryAll(".ref-hint").forEach(el=>hideRefHint(el)); } function hideRefHint(refHint) { const link = refHint.forLink; link.setAttribute("aria-expanded", "false"); if(refHint.teardownEventListeners) { refHint.teardownEventListeners(); } refHint.remove(); } function showRefHint(link) { if(link.classList.contains("dfn-link")) return; const url = link.getAttribute("href"); const refHintKey = link.getAttribute("data-refhint-key"); let key = url; if(refHintKey) { key = refHintKey + "_" + url; } const ref = refsData[key]; if(!ref) return; hideAllRefHints(); // Only display one at this time. const refHint = mkRefHint(link, ref); append(document.body, refHint); link.setAttribute("aria-expanded", "true"); positionRefHint(refHint); } function setupRefHintEventListeners(link, refHint) { if (refHint.teardownEventListeners) return; // Add event handlers to hide the refHint after the user moves away // from both the link and refHint, if not hovering either within one second. let timeout = null; const startHidingRefHint = (event) => { if (timeout) { clearTimeout(timeout); } timeout = setTimeout(() => { hideRefHint(refHint); }, 1000); } const resetHidingRefHint = (event) => { if (timeout) clearTimeout(timeout); timeout = null; }; link.addEventListener("mouseleave", startHidingRefHint); link.addEventListener("mouseenter", resetHidingRefHint); link.addEventListener("blur", startHidingRefHint); link.addEventListener("focus", resetHidingRefHint); refHint.addEventListener("mouseleave", startHidingRefHint); refHint.addEventListener("mouseenter", resetHidingRefHint); refHint.addEventListener("blur", startHidingRefHint); refHint.addEventListener("focus", resetHidingRefHint); refHint.teardownEventListeners = () => { // remove event listeners resetHidingRefHint(); link.removeEventListener("mouseleave", startHidingRefHint); link.removeEventListener("mouseenter", resetHidingRefHint); link.removeEventListener("blur", startHidingRefHint); link.removeEventListener("focus", resetHidingRefHint); refHint.removeEventListener("mouseleave", startHidingRefHint); refHint.removeEventListener("mouseenter", resetHidingRefHint); refHint.removeEventListener("blur", startHidingRefHint); refHint.removeEventListener("focus", resetHidingRefHint); }; } function positionRefHint(refHint) { const link = refHint.forLink; const linkPos = getBounds(link); refHint.style.top = linkPos.bottom + "px"; refHint.style.left = linkPos.left + "px"; const panelPos = refHint.getBoundingClientRect(); const panelMargin = 8; const maxRight = document.body.parentNode.clientWidth - panelMargin; if (panelPos.right > maxRight) { const overflowAmount = panelPos.right - maxRight; const newLeft = Math.max(panelMargin, linkPos.left - overflowAmount); refHint.style.left = newLeft + "px"; } } // TODO: shared util // Returns the root-level absolute position {left and top} of element. function getBounds(el, relativeTo=document.body) { const relativeRect = relativeTo.getBoundingClientRect(); const elRect = el.getBoundingClientRect(); const top = elRect.top - relativeRect.top; const left = elRect.left - relativeRect.left; return { top, left, bottom: top + elRect.height, right: left + elRect.width, } } function showRefHintListener(e) { // If the target isn't in a link (or is a link), // just ignore it. let link = e.target.closest("a"); if(!link) return; // If the target is in a ref-hint panel // (aka a link in the already-open one), // also just ignore it. if(link.closest(".ref-hint")) return; // Otherwise, show the panel for the link. showRefHint(link); } function hideAllHintsListener(e) { // If the click is inside a ref-hint panel, ignore it. if(e.target.closest(".ref-hint")) return; // Otherwise, close all the current panels. hideAllRefHints(); } document.addEventListener("DOMContentLoaded", () => { document.body.addEventListener("mousedown", showRefHintListener); document.body.addEventListener("focus", showRefHintListener); document.body.addEventListener("click", hideAllHintsListener); }); window.addEventListener("resize", () => { // Hide any open ref hint. hideAllRefHints(); }); } </script>