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<!doctype html><html lang="en">
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<title>CSS Animations Level 1</title>
<meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
<meta content="refining" name="csswg-work-status">
<meta content="ED" name="w3c-status">
<link href="../default.css" rel="stylesheet" type="text/css">
<link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">
<style>
body {
background-image: url("https://www.w3.org/StyleSheets/TR/logo-ED");
};
</style>
<meta content="Bikeshed 1.0.0" name="generator">
<script defer="" src="//test.csswg.org/harness/annotate.js#css-animations-1_dev/css-animations-1" type="text/javascript"></script>
<style type="text/css">
table.event-handlers {
border-collapse: collapse;
}
table.event-handlers th,
table.event-handlers td {
padding: 0.2em 1em;
}
table.event-handlers td {
border: 1px solid black;
}
</style>
<style>/* 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>/* style-counters */
.issue:not(.no-marker)::before {
content: "Issue " counter(issue);
}
.example:not(.no-marker)::before {
content: "Example";
content: "Example " counter(example);
}
.invalid.example:not(.no-marker)::before,
.illegal.example:not(.no-marker)::before {
content: "Invalid Example";
content: "Invalid Example" counter(example);
}</style>
<style>/* style-dfn-panel */
.dfn-panel {
display: inline-block;
position: absolute;
z-index: 35;
height: auto;
width: -webkit-fit-content;
max-width: 300px;
max-height: 500px;
overflow: auto;
padding: 0.5em 0.75em;
font: small Helvetica Neue, sans-serif, Droid Sans Fallback;
background: #DDDDDD;
color: black;
border: outset 0.2em;
}
.dfn-panel:not(.on) { display: none; }
.dfn-panel * { margin: 0; padding: 0; text-indent: 0; }
.dfn-panel > b { display: block; }
.dfn-panel a { color: black; }
.dfn-panel a:not(:hover) { text-decoration: none !important; border-bottom: none !important; }
.dfn-panel > b + b { margin-top: 0.25em; }
.dfn-panel > span { display: list-item; list-style: inside; }
.dfn-panel.activated {
display: inline-block;
position: fixed;
left: .5em;
bottom: .5em;
margin: 0 auto;
max-width: calc(100vw - 1.5em - .4em - .5em);
max-height: 30vh;
}
.dfn-paneled { cursor: pointer; }
</style>
<style>/* style-selflinks */
.heading, .issue, .note, .example, li, dt {
position: relative;
}
a.self-link {
position: absolute;
top: 0;
left: calc(-1 * (3.5rem - 26px));
width: calc(3.5rem - 26px);
height: 2em;
text-align: center;
border: none;
transition: opacity .2s;
opacity: .5;
}
a.self-link:hover {
opacity: 1;
}
.heading > a.self-link {
font-size: 83%;
}
li > a.self-link {
left: calc(-1 * (3.5rem - 26px) - 2em);
}
dfn > a.self-link {
top: auto;
left: auto;
opacity: 0;
width: 1.5em;
height: 1.5em;
background: gray;
color: white;
font-style: normal;
transition: opacity .2s, background-color .2s, color .2s;
}
dfn:hover > a.self-link {
opacity: 1;
}
dfn > a.self-link:hover {
color: black;
}
a.self-link::before { content: "¶"; }
.heading > a.self-link::before { content: "§"; }
dfn > a.self-link::before { content: "#"; }</style>
<style>/* style-autolinks */
.css.css, .property.property, .descriptor.descriptor {
color: #005a9c;
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;
}</style>
<body class="h-entry">
<div class="head">
<p data-fill-with="logo"><a class="logo" href="http://www.w3.org/"> <img alt="W3C" height="48" src="https://www.w3.org/StyleSheets/TR/2016/logos/W3C" width="72"> </a> </p>
<h1 class="p-name no-ref" id="title">CSS Animations Level 1</h1>
<h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Editor’s Draft, <time class="dt-updated" datetime="2016-05-13">13 May 2016</time></span></h2>
<div data-fill-with="spec-metadata">
<dl>
<dt>This version:
<dd><a class="u-url" href="https://drafts.csswg.org/css-animations/">https://drafts.csswg.org/css-animations/</a>
<dt>Latest published version:
<dd><a href="https://www.w3.org/TR/css3-animations/">https://www.w3.org/TR/css3-animations/</a>
<dt>Previous Versions:
<dd><a href="https://www.w3.org/TR/2013/WD-css3-animations-20130219/" rel="previous">https://www.w3.org/TR/2013/WD-css3-animations-20130219/</a>
<dd><a href="https://www.w3.org/TR/2012/WD-css3-animations-20120403/" rel="previous">https://www.w3.org/TR/2012/WD-css3-animations-20120403/</a>
<dt>Feedback:
<dd><span><a href="mailto:www-style@w3.org?subject=%5Bcss-animations%5D%20YOUR%20TOPIC%20HERE">www-style@w3.org</a> with subject line “<kbd>[css-animations] <i data-lt="">… message topic …</i></kbd>” (<a href="http://lists.w3.org/Archives/Public/www-style/" rel="discussion">archives</a>)</span>
<dt>Test Suite:
<dd><a href="http://test.csswg.org/suites/css-animations-1_dev/nightly-unstable/">http://test.csswg.org/suites/css-animations-1_dev/nightly-unstable/</a>
<dt>Issue Tracking:
<dd><a href="#issues-index">Inline In Spec</a>
<dt class="editor">Editors:
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:dino@apple.com">Dean Jackson</a> (<span class="p-org org">Apple Inc.</span>)
<dd class="editor p-author h-card vcard"><a class="p-name fn u-url url" href="http://dbaron.org/">L. David Baron</a> (<span class="p-org org">Mozilla</span>)
<dd class="editor p-author h-card vcard"><a class="p-name fn u-url url" href="http://xanthir.com/contact/">Tab Atkins Jr.</a> (<span class="p-org org">Google</span>)
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:bbirtles@mozilla.com">Brian Birtles</a> (<span class="p-org org">Mozilla Japan</span>)
<dt class="editor">Former Editors:
<dd class="editor p-author h-card vcard"><span class="p-name fn">David Hyatt</span> (<span class="p-org org">Apple Inc.</span>)
<dd class="editor p-author h-card vcard"><span class="p-name fn">Chris Marrin</span> (<span class="p-org org">Apple Inc.</span>)
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:galineau@adobe.com">Sylvain Galineau</a> (<span class="p-org org">Adobe</span>)
<dt>Issues List:
<dd><span><a href="https://www.w3.org/Bugs/Public/buglist.cgi?component=Animations&list_id=36653&product=CSS&query_format=advanced&resolution=---">In Bugzilla</a></span>
<dd><span></span>
</dl>
</div>
<div data-fill-with="warning"></div>
<p class="copyright" data-fill-with="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2016 <a href="http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>, <a href="http://ev.buaa.edu.cn/">Beihang</a>). W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply. </p>
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
<div class="p-summary" data-fill-with="abstract">
<p>This CSS module describes a way for authors to animate the values of CSS properties over time, using keyframes. The behavior of these keyframe animations can be controlled by specifying their duration, number of repeats, and repeating behavior.</p>
<a href="http://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, in speech, etc.
</div>
<h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>
<div data-fill-with="status">
<p> 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. </p>
<p> The (<a href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public mailing list <a href="mailto:www-style@w3.org?Subject=%5Bcss-animations%5D%20PUT%20SUBJECT%20HERE">www-style@w3.org</a> (see <a href="http://www.w3.org/Mail/Request">instructions</a>)
is preferred for discussion of this specification.
When sending e-mail,
please put the text “css-animations” in the subject,
preferably like this:
“[css-animations] <em>…summary of comment…</em>” </p>
<p> This document was produced by the <a href="http://www.w3.org/Style/CSS/members">CSS Working Group</a> (part of the <a href="http://www.w3.org/Style/">Style Activity</a>). </p>
<p> This document was produced by a group operating under
the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent Policy</a>.
W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/32061/status" rel="disclosure">public list of any patent disclosures</a> made in connection with the deliverables of the group;
that page also includes instructions for disclosing a patent.
An individual who has actual knowledge of a patent which the individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the W3C Patent Policy</a>. </p>
<p> This document is governed by the <a href="http://www.w3.org/2015/Process-20150901/" id="w3c_process_revision">1 September 2015 W3C Process Document</a>. </p>
<p></p>
</div>
<div data-fill-with="at-risk">
<p>The following features are at-risk, and may be dropped during the CR period: </p>
<ul>
<li>the <code>pseudoElement</code> property of the <span class="css">AnimationEvent</span> interface
<li>
</ul>
<p>“At-risk” is a W3C Process term-of-art, and does not necessarily imply that the feature is in danger of being dropped or delayed. It means that the WG believes the feature may have difficulty being interoperably implemented in a timely manner, and marking it as such allows the WG to drop the feature if necessary when transitioning to the Proposed Rec stage, without having to publish a new Candidate Rec without the feature first.</p>
</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"><span class="secno">1</span> <span class="content"> Introduction</span></a>
<li><a href="#values"><span class="secno">2</span> <span class="content"> Values</span></a>
<li><a href="#animations"><span class="secno">3</span> <span class="content"> Animations</span></a>
<li>
<a href="#keyframes"><span class="secno">4</span> <span class="content"> Keyframes</span></a>
<ol class="toc">
<li><a href="#timing-functions"><span class="secno">4.1</span> <span class="content"> Timing functions for keyframes</span></a>
<li><a href="#animation-name"><span class="secno">4.2</span> <span class="content"> The <span class="property">animation-name</span> property</span></a>
<li><a href="#animation-duration"><span class="secno">4.3</span> <span class="content"> The <span class="property">animation-duration</span> property</span></a>
<li><a href="#animation-timing-function"><span class="secno">4.4</span> <span class="content"> The <span class="property">animation-timing-function</span> property</span></a>
<li><a href="#animation-iteration-count"><span class="secno">4.5</span> <span class="content"> The <span class="property">animation-iteration-count</span> property</span></a>
<li><a href="#animation-direction"><span class="secno">4.6</span> <span class="content"> The <span class="property">animation-direction</span> property</span></a>
<li><a href="#animation-play-state"><span class="secno">4.7</span> <span class="content"> The <span class="property">animation-play-state</span> property</span></a>
<li><a href="#animation-delay"><span class="secno">4.8</span> <span class="content"> The <span class="property">animation-delay</span> property</span></a>
<li><a href="#animation-fill-mode"><span class="secno">4.9</span> <span class="content"> The <span class="property">animation-fill-mode</span> property</span></a>
<li><a href="#animation"><span class="secno">4.10</span> <span class="content"> The <span class="property">animation</span> shorthand property</span></a>
</ol>
<li>
<a href="#events"><span class="secno">5</span> <span class="content"> Animation Events</span></a>
<ol class="toc">
<li>
<a href="#interface-animationevent"><span class="secno">5.1</span> <span class="content"> The <code>AnimationEvent</code> Interface</span></a>
<ol class="toc">
<li><a href="#interface-animationevent-idl"><span class="secno">5.1.1</span> <span class="content"> IDL Definition</span></a>
<li><a href="#interface-animationevent-attributes"><span class="secno">5.1.2</span> <span class="content"> Attributes</span></a>
</ol>
<li>
<a href="#event-animationevent"><span class="secno">5.2</span> <span class="content"> Types of <code>AnimationEvent</code></span></a>
<ol class="toc">
<li><a href="#event-handlers-on-elements-document-objects-and-window-objects"><span class="secno">5.2.1</span> <span class="content">Event handlers on elements, <code>Document</code> objects, and <code>Window</code> objects</span></a>
</ol>
</ol>
<li>
<a href="#interface-dom"><span class="secno">6</span> <span class="content"> DOM Interfaces</span></a>
<ol class="toc">
<li>
<a href="#interface-cssrule"><span class="secno">6.1</span> <span class="content"> The <code>CSSRule</code> Interface</span></a>
<ol class="toc">
<li><a href="#interface-cssrule-idl"><span class="secno">6.1.1</span> <span class="content"> IDL Definition</span></a>
</ol>
<li>
<a href="#interface-csskeyframerule"><span class="secno">6.2</span> <span class="content"> The <code>CSSKeyframeRule</code> Interface</span></a>
<ol class="toc">
<li><a href="#interface-csskeyframerule-idl"><span class="secno">6.2.1</span> <span class="content"> IDL Definition</span></a>
<li><a href="#interface-csskeyframerule-attributes"><span class="secno">6.2.2</span> <span class="content"> Attributes</span></a>
</ol>
<li>
<a href="#interface-csskeyframesrule"><span class="secno">6.3</span> <span class="content"> The <code>CSSKeyframesRule</code> Interface</span></a>
<ol class="toc">
<li><a href="#interface-csskeyframesrule-idl"><span class="secno">6.3.1</span> <span class="content"> IDL Definition</span></a>
<li><a href="#interface-csskeyframesrule-attributes"><span class="secno">6.3.2</span> <span class="content"> Attributes</span></a>
<li><a href="#interface-csskeyframesrule-appendrule"><span class="secno">6.3.3</span> <span class="content"> The <code>appendRule</code> method</span></a>
<li><a href="#interface-csskeyframesrule-deleterule"><span class="secno">6.3.4</span> <span class="content"> The <code>deleteRule</code> method</span></a>
<li><a href="#interface-csskeyframesrule-findrule"><span class="secno">6.3.5</span> <span class="content"> The <code>findRule</code> method</span></a>
</ol>
<li>
<a href="#interface-globaleventhandlers"><span class="secno">6.4</span> <span class="content"> Extensions to the <code>GlobalEventHandlers</code> Interface</span></a>
<ol class="toc">
<li><a href="#interface-globaleventhandlers-idl"><span class="secno">6.4.1</span> <span class="content"> IDL Definition</span></a>
</ol>
</ol>
<li><a href="#acknowledgements"><span class="secno">7</span> <span class="content"> Acknowledgements</span></a>
<li><a href="#other-open-issues"><span class="secno">8</span> <span class="content">Other open issues</span></a>
<li><a href="#wg-resolutions-pending"><span class="secno">9</span> <span class="content"> Working Group Resolutions that are pending editing</span></a>
<li>
<a href="#conformance"><span class="secno"></span> <span class="content"> Conformance</span></a>
<ol class="toc">
<li><a href="#document-conventions"><span class="secno"></span> <span class="content"> Document conventions</span></a>
<li><a href="#conform-classes"><span class="secno"></span> <span class="content"> Conformance classes</span></a>
<li>
<a href="#conform-responsible"><span class="secno"></span> <span class="content"> Requirements for Responsible Implementation of CSS</span></a>
<ol class="toc">
<li><a href="#conform-partial"><span class="secno"></span> <span class="content"> Partial Implementations</span></a>
<li><a href="#conform-future-proofing"><span class="secno"></span> <span class="content"> Implementations of Unstable and Proprietary Features</span></a>
<li><a href="#conform-testing"><span class="secno"></span> <span class="content"> Implementations of CR-level Features</span></a>
</ol>
</ol>
<li>
<a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
<ol class="toc">
<li><a href="#index-defined-here"><span class="secno"></span> <span class="content">Terms defined by this specification</span></a>
<li><a href="#index-defined-elsewhere"><span class="secno"></span> <span class="content">Terms defined by reference</span></a>
</ol>
<li>
<a href="#references"><span class="secno"></span> <span class="content">References</span></a>
<ol class="toc">
<li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
<li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
</ol>
<li><a href="#property-index"><span class="secno"></span> <span class="content">Property Index</span></a>
<li><a href="#idl-index"><span class="secno"></span> <span class="content">IDL Index</span></a>
<li><a href="#issues-index"><span class="secno"></span> <span class="content">Issues Index</span></a>
</ol>
</nav>
<main>
<h2 class="heading settled" data-level="1" id="intro"><span class="secno">1. </span><span class="content"> Introduction</span><a class="self-link" href="#intro"></a></h2>
<p><em>This section is not normative</em></p>
<p>CSS Transitions <a data-link-type="biblio" href="#biblio-css3-transitions">[CSS3-TRANSITIONS]</a> provide a way to interpolate
CSS property values when they change as a result of underlying
property changes. This provides an easy way to do simple animation,
but the start and end states of the animation are controlled by the
existing property values, and transitions provide little control to
the author on how the animation progresses.</p>
<p>This proposal introduces defined animations, in which the author can
specify the changes in CSS properties over time as a set of keyframes.
Animations are similar to transitions in that they change the
presentational value of CSS properties over time. The principal difference
is that while transitions trigger implicitly when property values change,
animations are explicitly executed when the animation properties are applied.
Because of this, animations require explicit values for the properties
being animated. These values are specified using animation keyframes,
described below.</p>
<p>Many aspects of the animation can be controlled, including how many times
the animation iterates, whether or not it alternates between the begin and
end values, and whether or not the animation should be running or paused.
An animation can also delay its start time.</p>
<h2 class="heading settled" data-level="2" id="values"><span class="secno">2. </span><span class="content"> Values</span><a class="self-link" href="#values"></a></h2>
<p>This specification follows the CSS property definition conventions
from <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a>. Value types not defined in this specification are
defined in CSS Level 2 Revision 1 <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a>. Other CSS modules may
expand the definitions of these value types: for example <a data-link-type="biblio" href="#biblio-css3val">[CSS3VAL]</a>,
when combined with this module, expands the definition of the <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#length-value" title="Expands to: em | advance measure | ch | vmin | cm | pc | pixel unit | in | rem | q | vh | ex | pt | vw | vmax | mm"><length></a> value type as used in this specification.</p>
<p>In addition to the property-specific values listed in their definitions,
all properties defined in this specification also accept the <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-cascade-4/#valdef-all-initial">initial</a> and <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-cascade-4/#valdef-all-inherit">inherit</a> keyword as their property value. For readability it has
not been repeated explicitly.</p>
<h2 class="heading settled" data-level="3" id="animations"><span class="secno">3. </span><span class="content"> Animations</span><a class="self-link" href="#animations"></a></h2>
<p>CSS Animations affect computed property values. This effect happens by
adding a specified value to the CSS cascade (<a data-link-type="biblio" href="#biblio-css3cascade">[CSS3CASCADE]</a>) (at the
level for CSS Animations) that will produce the correct computed value
for the current state of the animation. As defined in <a data-link-type="biblio" href="#biblio-css3cascade">[CSS3CASCADE]</a>,
animations override all normal rules, but are overridden by !important
rules.</p>
<p>If at some point in time there are multiple animations specifying behavior
for the same property, the animation which occurs last in the value
of <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-1">animation-name</a> will override the other animations at that point.</p>
<p>An animation does not affect the computed value before the application of the
animation (that is, when the <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-2">animation-name</a> property is set on an element)
or after it is removed. Furthermore, typically an animation does not affect
the computed value before the animation delay has expired or after the end of
the animation, but may do so depending on the <a class="property" data-link-type="propdesc" href="#propdef-animation-fill-mode" id="ref-for-propdef-animation-fill-mode-1">animation-fill-mode</a> property.</p>
<p>While running, the animation computes the value of those properties
it animates. Other values may take precedence over the animated value
according to the CSS cascade (<a data-link-type="biblio" href="#biblio-css3cascade">[CSS3CASCADE]</a>).</p>
<p>While an animation is applied but has not finished, or has finished but has
an <a class="property" data-link-type="propdesc" href="#propdef-animation-fill-mode" id="ref-for-propdef-animation-fill-mode-2">animation-fill-mode</a> of <a class="css" data-link-type="maybe" href="#valdef-animation-fill-mode-forwards" id="ref-for-valdef-animation-fill-mode-forwards-1">forwards</a> or <a class="css" data-link-type="maybe" href="#valdef-animation-fill-mode-both" id="ref-for-valdef-animation-fill-mode-both-1">both</a>, the user agent must act
as if the <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css-will-change-1/#propdef-will-change">will-change</a> property (<a data-link-type="biblio" href="
2B2
#biblio-css-will-change-1">[css-will-change-1]</a>) on the element
additionally includes all the properties animated by the animation.</p>
<p>The start time of an animation is the time at which the style applying
the animation and the corresponding @keyframes rule are both resolved.
If an animation is specified for an element but the corresponding
@keyframes rule does not yet exist, the animation cannot start; the
animation will start from the beginning as soon as a matching @keyframes
rule can be resolved. An animation specified by dynamically modifying the
element’s style will start when this style is resolved; that may be
immediately in the case of a pseudo style rule such as hover, or may be
when the scripting engine returns control to the browser (in the case of
style applied by script). Note that dynamically updating keyframe style
rules does not start or re-start an animation.</p>
<p>An animation applies to an element if its name appears as one of the
identifiers in the computed value of the <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-3">animation-name</a> property and the
animation uses a valid @keyframes rule. Once an
animation has started it continues until it ends or the <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-4">animation-name</a> is
removed. Changes to the values of animation properties while the animation
is running apply as if the animation had those values from when it
began. For example, shortening the <a class="property" data-link-type="propdesc" href="#propdef-animation-delay" id="ref-for-propdef-animation-delay-1">animation-delay</a> may cause the animation
to jump forwards or even finish immediately and dispatch an <a data-link-type="idl" href="#eventdef-animationevent-animationend" id="ref-for-eventdef-animationevent-animationend-1">animationend</a> event.
Conversely, extending the <a class="property" data-link-type="propdesc" href="#propdef-animation-delay" id="ref-for-propdef-animation-delay-2">animation-delay</a> may cause an animation to
re-start and dispatch an <a data-link-type="idl" href="#eventdef-animationevent-animationstart" id="ref-for-eventdef-animationevent-animationstart-1">animationstart</a> event.</p>
<p>The same @keyframes rule name may be repeated within an <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-5">animation-name</a>.
Changes to the <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-6">animation-name</a> update existing animations by iterating over
the new list of animations from last to first, and, for each animation,
finding the <em>last</em> matching animation in the list of existing
animations.
If a match is found, the existing animation is updated using the animation
properties corresponding to its position in the new list of animations,
whilst maintaining its current playback time as described above.
The matching animation is removed from the existing list of animations such
that it will not match twice.
If a match is not found, a new animation is created.
As a result, updating <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-7">animation-name</a> from ‘a’ to
‘a, a’ will cause the existing animation for ‘a’ to
become the <em>second</em> animation in the list and a new animation will be
created for the first item in the list.</p>
<div class="example" id="example-dee38741">
<a class="self-link" href="#example-dee38741"></a>
<pre>div {
animation-name: diagonal-slide;
animation-duration: 5s;
animation-iteration-count: 10;
}
@keyframes diagonal-slide {
from {
left: 0;
top: 0;
}
to {
left: 100px;
top: 100px;
}
}
</pre>
<p>This will produce an animation that moves an element from (0, 0) to
(100px, 100px) over five seconds and repeats itself nine times
(for a total of ten iterations).</p>
</div>
<p>Setting the <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css2/visuren.html#propdef-display">display</a> property to <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-display-3/#valdef-display-none">none</a> will terminate any running animation applied
to the element and its descendants. If an element has a <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css2/visuren.html#propdef-display">display</a> of <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-display-3/#valdef-display-none">none</a>, updating <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css2/visuren.html#propdef-display">display</a> to a value other than <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-display-3/#valdef-display-none">none</a> will start all animations applied to the element
by the <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-8">animation-name</a> property, as well as all animations applied to descendants
with <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css2/visuren.html#propdef-display">display</a> other than <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-display-3/#valdef-display-none">none</a>.</p>
<p>While authors can use animations to create dynamically changing content, dynamically
changing content can lead to seizures in some users. For information on how to avoid
content that can lead to seizures, see Guideline 2.3: Seizures: Do not design content
in a way that is known to cause seizures (<a data-link-type="biblio" href="#biblio-wcag20">[WCAG20]</a>).</p>
<p>Implementations may ignore animations when the rendering medium is not interactive e.g. when printed.
A future version of this specification may define how to render animations for these media.</p>
<h2 class="heading settled" data-level="4" id="keyframes"><span class="secno">4. </span><span class="content"> Keyframes</span><a class="self-link" href="#keyframes"></a></h2>
<p>Keyframes are used to specify the values for the animating properties at various points
during the animation. The keyframes specify the behavior of one cycle of the animation;
the animation may iterate zero or more times.</p>
<p>Keyframes are specified using a specialized CSS at-rule. A <dfn class="dfn-paneled css" data-dfn-type="at-rule" data-export="" data-lt="@keyframes" id="at-ruledef-keyframes">@keyframes<span class="dfn-panel" data-deco=""><b><a href="#at-ruledef-keyframes">#at-ruledef-keyframes</a></b><b>Referenced in:</b><span><a href="#ref-for-at-ruledef-keyframes-1">6.3.3.
The appendRule method</a></span></span></dfn> rule consists of the
keyword "@keyframes", followed by an identifier giving a name for the animation (which will
be referenced using <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-9">animation-name</a>), followed by a set of style rules (delimited by curly
braces).</p>
<p>The keyframe selector for a keyframe style rule consists of a comma-separated list of
percentage values or the keywords <span class="css">from</span> or <span class="css">to</span>. The selector is used to specify the
percentage along the duration of the animation that the keyframe represents. The keyframe
itself is specified by the block of property values declared on the selector. The keyword <span class="css">from</span> is equivalent to the value <span class="css">0%</span>. The keyword <span class="css">to</span> is equivalent to the value <span class="css">100%</span>. <span class="note" role="note">Note that the percentage unit specifier must be used on percentage values.
Therefore, <span class="css">0</span> is an invalid keyframe selector.</span></p>
<p>If a <span class="css">0%</span> or <span class="css">from</span> keyframe is not specified, then the user agent constructs a <span class="css">0%</span> keyframe
using the computed values of the properties being animated. If a <span class="css">100%</span> or <span class="css">to</span> keyframe is not
specified, then the user agent constructs a <span class="css">100%</span> keyframe using the computed values of the
properties being animated. If a keyframe selector specifies negative percentage values or values
higher than <span class="css">100%</span>, then the keyframe will be ignored.</p>
<p>The keyframe declaration block for a keyframe rule consists of properties and values. The properties
defined by this specification are ignored in these rules, with the exception of <a class="property" data-link-type="propdesc" href="#propdef-animation-timing-function" id="ref-for-propdef-animation-timing-function-1">animation-timing-function</a>, the behavior of which is described below. In addition, keyframe rule
declarations qualified with !important are ignored.</p>
<p>The @keyframes rule that is used by an animation will be the last one encountered in sorted rules
order that matches the name of the animation specified by the <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-10">animation-name</a> property.</p>
<div class="example" id="example-06c21004">
<a class="self-link" href="#example-06c21004"></a>
<pre>div {
animation-name: slide-right;
animation-duration: 2s;
}
@keyframes slide-right {
from {
margin-left: 0px;
}
50% {
margin-left: 110px;
opacity: 1;
}
50% {
opacity: 0.9;
}
to {
margin-left: 200px;
}
}
</pre>
<p>At the 1s mark, the slide-right animation will have the same state as if we had defined the 50% rule like this:</p>
<pre>@keyframes slide-right {
50% {
margin-left: 110px;
opacity: 0.9;
}
to {
margin-left: 200px;
}
}
</pre>
</div>
<p>To determine the set of keyframes, all of the values in the selectors are sorted in increasing order
by time. The rules within the @keyframes rule then cascade; the properties of a keyframe may thus derive
from more than one @keyframes rule with the same selector value.</p>
<p>If a property is not specified for a keyframe, or is specified but invalid, the animation of that
property proceeds as if that keyframe did not exist. Conceptually, it is as if a set of keyframes is
constructed for each property that is present in any of the keyframes, and an animation is run
independently for each property.</p>
<div class="example" id="example-25879023">
<a class="self-link" href="#example-25879023"></a>
<pre>@keyframes wobble {
0% {
left: 100px;
}
40% {
left: 150px;
}
60% {
left: 75px;
}
100% {
left: 100px;
}
}
</pre>
<p>Four keyframes are specified for the animation named "wobble". In the first keyframe,
shown at the beginning of the animation cycle, the value of the <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css-position-3/#propdef-left">left</a> property being
animated is <span class="css">100px</span>. By 40% of the animation duration, <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css-position-3/#propdef-left">left</a> has animated to <span class="css">150px</span>.
At 60% of the animation duration, <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css-position-3/#propdef-left">left</a> has animated back to <span class="css">75px</span>. At the end of the
animation cycle, the value of <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css-position-3/#propdef-left">left</a> has returned to <span class="css">100px</span>. The diagram below shows
the state of the animation if it were given a duration of <span class="css">10s</span>.</p>
<figure>
<img alt="" src="./animation1.png">
<figcaption>Animation states specified by keyframes</figcaption>
</figure>
</div>
<p>The following is the grammar for the keyframes rule:</p>
<pre>keyframes_rule: KEYFRAMES_SYM S+ IDENT S* '{' S* keyframes_blocks '}' S*;
keyframes_blocks: [ keyframe_selector '{' S* declaration? [ ';' S* declaration? ]* '}' S* ]* ;
keyframe_selector: [ FROM_SYM | TO_SYM | PERCENTAGE ] S* [ ',' S* [ FROM_SYM | TO_SYM | PERCENTAGE ] S* ]*;
@{K}{E}{Y}{F}{R}{A}{M}{E}{S} {return KEYFRAMES_SYM;}
{F}{R}{O}{M} {return FROM_SYM;}
{T}{O} {return TO_SYM;}
</pre>
<p class="issue" id="issue-396f31a3"><a class="self-link" href="#issue-396f31a3"></a> This specification needs to define
how the value is determined from the keyframes,
like the section on <a href="https://drafts.csswg.org/css-transitions/#application">Application of transitions</a> does for CSS Transitions. </p>
<h3 class="heading settled" data-level="4.1" id="timing-functions"><span class="secno">4.1. </span><span class="content"> Timing functions for keyframes</span><a class="self-link" href="#timing-functions"></a></h3>
<p>A keyframe style rule may also declare the timing function that is to be used as the animation
moves to the next keyframe.</p>
<div class="example" id="example-5d14f501">
<a class="self-link" href="#example-5d14f501"></a>
<pre>@keyframes bounce {
from {
top: 100px;
animation-timing-function: ease-out;
}
25% {
top: 50px;
animation-timing-function: ease-in;
}
50% {
top: 100px;
animation-timing-function: ease-out;
}
75% {
top: 75px;
animation-timing-function: ease-in;
}
to {
top: 100px;
}
}
</pre>
<p>Five keyframes are specified for the animation named "bounce". Between the first and second
keyframe (i.e., between 0% and 25%) an ease-out timing function is used. Between the second
and third keyframe (i.e., between 25% and 50%) an ease-in timing function is used. And so on.
The effect will appear as an element that moves up the page 50px, slowing down as it reaches
its highest point then speeding up as it falls back to 100px. The second half of the animation
behaves in a similar manner, but only moves the el
8348
ement 25px up the page.</p>
</div>
<p>A timing function specified on the <span class="css">to</span> or <span class="css">100%</span> keyframe is ignored.</p>
<p>See the <a class="property" data-link-type="propdesc" href="#propdef-animation-timing-function" id="ref-for-propdef-animation-timing-function-2">animation-timing-function</a> property for more information.</p>
<h3 class="heading settled" data-level="4.2" id="animation-name"><span class="secno">4.2. </span><span class="content"> The <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-11">animation-name</a> property</span><a class="self-link" href="#animation-name"></a></h3>
<p>The <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-12">animation-name</a> property defines a list of animations that apply. Each name is used to select
the keyframe at-rule that provides the property values for the animation. If the name does not match
any keyframe at-rule, there are no properties to be animated and the animation will not execute.
Furthermore, if the animation name is <code>none</code> then there will be no animation. This can be
used to override any animations coming from the cascade. If multiple animations are attempting to
modify the same property, then the animation closest to the end of the list of names wins.</p>
<p>Each animation listed by name should have a corresponding value for the other animation properties
listed below. If the lists of values for the other animation properties do not have the same length,
the length of the <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-13">animation-name</a> list determines the number of items in each list examined when
starting animations. The lists are matched up from the first value: excess values at the end are not
used. If one of the other properties doesn’t have enough comma-separated values to match the number of
values of <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-14">animation-name</a>, the UA must calculate its used value by repeating the list of values until
there are enough. This truncation or repetition does not affect the computed value.</p>
<p class="note" role="note">Note: This is analogous to the behavior of the <a class="property" data-link-type="propdesc">background-*</a> properties, with <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css-backgrounds-3/#background-image">background-image</a> analogous to <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-15">animation-name</a>.</p>
<table class="def propdef" data-link-for-hint="animation-name">
<tbody>
<tr>
<th>Name:
<td><dfn class="dfn-paneled css" data-dfn-type="property" data-export="" data-lt="animation-name" id="propdef-animation-name">animation-name<span class="dfn-panel" data-deco=""><b><a href="#propdef-animation-name">#propdef-animation-name</a></b><b>Referenced in:</b><span><a href="#ref-for-propdef-animation-name-1">3.
Animations</a> <a href="#ref-for-propdef-animation-name-2">(2)</a> <a href="#ref-for-propdef-animation-name-3">(3)</a> <a href="#ref-for-propdef-animation-name-4">(4)</a> <a href="#ref-for-propdef-animation-name-5">(5)</a> <a href="#ref-for-propdef-animation-name-6">(6)</a> <a href="#ref-for-propdef-animation-name-7">(7)</a> <a href="#ref-for-propdef-animation-name-8">(8)</a></span><span><a href="#ref-for-propdef-animation-name-9">4.
Keyframes</a> <a href="#ref-for-propdef-animation-name-10">(2)</a></span><span><a href="#ref-for-propdef-animation-name-11">4.2.
The animation-name property</a> <a href="#ref-for-propdef-animation-name-12">(2)</a> <a href="#ref-for-propdef-animation-name-13">(3)</a> <a href="#ref-for-propdef-animation-name-14">(4)</a> <a href="#ref-for-propdef-animation-name-15">(5)</a> <a href="#ref-for-propdef-animation-name-16">(6)</a></span><span><a href="#ref-for-propdef-animation-name-17">4.9.
The animation-fill-mode property</a></span><span><a href="#ref-for-propdef-animation-name-18">4.10.
The animation shorthand property</a> <a href="#ref-for-propdef-animation-name-19">(2)</a> <a href="#ref-for-propdef-animation-name-20">(3)</a> <a href="#ref-for-propdef-animation-name-21">(4)</a> <a href="#ref-for-propdef-animation-name-22">(5)</a> <a href="#ref-for-propdef-animation-name-23">(6)</a></span><span><a href="#ref-for-propdef-animation-name-24">5.
Animation Events</a> <a href="#ref-for-propdef-animation-name-25">(2)</a> <a href="#ref-for-propdef-animation-name-26">(3)</a> <a href="#ref-for-propdef-animation-name-27">(4)</a></span><span><a href="#ref-for-propdef-animation-name-28">5.1.2.
Attributes</a></span><span><a href="#ref-for-propdef-animation-name-29">6.3.2.
Attributes</a> <a href="#ref-for-propdef-animation-name-30">(2)</a></span></span></dfn>
<tr class="value">
<th>Value:
<td class="prod"><a class="production css" data-link-type="type" href="#typedef-single-animation-name" id="ref-for-typedef-single-animation-name-1"><single-animation-name></a><a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-comma">#</a>
<tr>
<th>Initial:
<td>none
<tr>
<th>Applies to:
<td>all elements, ::before and ::after pseudo-elements
<tr>
<th>Inherited:
<td>none
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>interactive
<tr>
<th>Computed value:
<td>As specified
<tr>
<th>Animatable:
<td>no
<tr>
<th>Canonical order:
<td>per grammar
</table>
<p><dfn class="dfn-paneled css" data-dfn-type="type" data-export="" data-lt="<single-animation-name>" id="typedef-single-animation-name"><single-animation-name><span class="dfn-panel" data-deco=""><b><a href="#typedef-single-animation-name">#typedef-single-animation-name</a></b><b>Referenced in:</b><span><a href="#ref-for-typedef-single-animation-name-1">4.2.
The animation-name property</a></span><span><a href="#ref-for-typedef-single-animation-name-2">4.10.
The animation shorthand property</a> <a href="#ref-for-typedef-single-animation-name-3">(2)</a></span></span></dfn> = none | <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#identifier-value"><custom-ident></a></p>
<p>The values of <a class="property" data-link-type="propdesc" href="#propdef-animation-name" id="ref-for-propdef-animation-name-16">animation-name</a> have the following meanings:</p>
<dl>
<dt><dfn class="dfn-paneled css" data-dfn-for="animation-name" data-dfn-type="value" data-export="" data-lt="none" id="valdef-animation-name-none">none<span class="dfn-panel" data-deco=""><b><a href="#valdef-animation-name-none">#valdef-animation-name-none</a></b><b>Referenced in:</b><span><a href="#ref-for-valdef-animation-name-none-1">4.10.
The animation shorthand property</a></span></span></dfn>
<dd> No keyframes are specified at all, so there will be no animation.
Any other animations properties specified for this animation have no effect.
<dt><dfn class="css" data-dfn-for="animation-name" data-dfn-type="value" data-export="" id="valdef-animation-name-custom-ident"><a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#identifier-value"><custom-ident></a><a class="self-link" href="#valdef-animation-name-custom-ident"></a></dfn>
<dd>
The animation will use the keyframes with the name specified by the <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#identifier-value"><custom-ident></a>,
if they exist.If no such keyframes exist, there is no animation.
<p>The <a href="https://www.w3.org/TR/css3-values/#common-keywords">CSS-wide keywords</a> and keywords defined by this property are not valid animation names.</p>
</dl>
<h3 class="heading settled" data-level="4.3" id="animation-duration"><span class="secno">4.3. </span><span class="content"> The <a class="property" data-link-type="propdesc" href="#propdef-animation-duration" id="ref-for-propdef-animation-duration-1">animation-duration</a> property</span><a class="self-link" href="#animation-duration"></a></h3>
<p>The <a class="property" data-link-type="propdesc" href="#propdef-animation-duration" id="ref-for-propdef-animation-duration-2">animation-duration</a> property defines duration of a single animation cycle.</p>
<table class="def propdef" data-link-for-hint="animation-duration">
<tbody>
<tr>
<th>Name:
<td><dfn class="dfn-paneled css" data-dfn-type="property" data-export="" data-lt="animation-duration" id="propdef-animation-duration">animation-duration<span class="dfn-panel" data-deco=""><b><a href="#propdef-animation-duration">#propdef-animation-duration</a></b><b>Referenced in:</b><span><a href="#ref-for-propdef-animation-duration-1">4.3.
The animation-duration property</a> <a href="#ref-for-propdef-animation-duration-2">(2)</a></span><span><a href="#ref-for-propdef-animation-duration-3">4.5.
The animation-iteration-count property</a></span><span><a href="#ref-for-propdef-animation-duration-4">4.9.
The animation-fill-mode property</a></span><span><a href="#ref-for-propdef-animation-duration-5">4.10.
The animation shorthand property</a></span></span></dfn>
<tr class="value">
<th>Value:
<td class="prod"><a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#time-value" title="Expands to: s | ms"><time></a><a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-comma">#</a>
<tr>
<th>Initial:
<td>0s
<tr>
<th>Applies to:
<td>all elements, ::before and ::after pseudo-elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>interactive
<tr>
<th>Computed value:
<td>As specified
<tr>
<th>Animatable:
<td>no
<tr>
<th>Canonical order:
<td>per grammar
</table>
<dl>
<dt><dfn class="css" data-dfn-for="animation-duration" data-dfn-type="value" data-export="" id="valdef-animation-duration-time"><a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#time-value" title="Expands to: s | ms"><time></a><a class="self-link" href="#valdef-animation-duration-time"></a></dfn>
<dd>
The <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#time-value" title="Expands to: s | ms"><time></a> specifies the length of time that an animation takes to complete one cycle.
A negative <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#time-value" title="Expands to: s | ms"><time></a> is invalid.
<p>If the <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#time-value" title="Expands to: s | ms"><time></a> is <span class="css">0s</span>, like the initial value,
the keyframes of the animation have no effect,
but the animation itself still occurs instantaneously.
Specifically, start and end events are fired; if <a class="property" data-link-type="propdesc" href="#propdef-animation-fill-mode" id="ref-for-propdef-animation-fill-mode-3">animation-fill-mode</a> is set to <a class="css" data-link-type="maybe" href="#valdef-animation-fill-mode-backwards" id="ref-for-valdef-animation-fill-mode-backwards-1">backwards</a> or <a class="css" data-link-type="maybe" href="#valdef-animation-fill-mode-both" id="ref-for-valdef-animation-fill-mode-both-2">both</a>, the first frame of the animation, as defined by <a class="property" data-link-type="propdesc" href="#propdef-animation-direction" id="ref-for-propdef-animation-direction-1">animation-direction</a>, will be displayed during the <a class="property" data-link-type="propdesc" href="#propdef-animation-delay" id="ref-for-propdef-animation-delay-3">animation-delay</a>. Then the last frame of the animation,
as defined by <a class="property" data-link-type="propdesc" href="#propdef-animation-direction" id="ref-for-propdef-animation-direction-2">animation-direction</a>, will be displayed if <a class="property" data-link-type="propdesc" href="#propdef-animation-fill-mode" id="ref-for-propdef-animation-fill-mode-4">animation-fill-mode</a> is set to <a class="css" data-link-type="maybe" href="#valdef-animation-fill-mode-forwards" id="ref-for-valdef-animation-fill-mode-forwards-2">forwards</a> or <a class="css" data-link-type="maybe" href="#valdef-animation-fill-mode-both" id="ref-for-valdef-animation-fill-mode-both-3">both</a>.
If <a class="property" data-link-type="propdesc" href="#propdef-animation-fill-mode" id="ref-for-propdef-animation-fill-mode-5">animation-fill-mode</a> is set to <a class="css" data-link-type="maybe" href="#valdef-animation-fill-mode-none" id="ref-for-valdef-animation-fill-mode-none-1">none</a> then the animation has no visible effect.</p>
</dl>
<h3 class="heading settled" data-level="4.4" id="animation-timing-function"><span class="secno">4.4. </span><span class="content"> The <a class="property" data-link-type="propdesc" href="#propdef-animation-timing-function" id="ref-for-propdef-animation-timing-function-3">animation-timing-function</a> property</span><a class="self-link" href="#animation-timing-function"></a></h3>
<p>The <a class="property" data-link-type="propdesc" href="#propdef-animation-timing-function" id="ref-for-propdef-animation-timing-function-4">animation-timing-function</a> property describes how the animation will progress over
one cycle of its duration. See the <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css-transitions-1/#propdef-transition-timing-function">transition-timing-function</a> property <a data-link-type="biblio" href="#biblio-css3-transitions">[CSS3-TRANSITIONS]</a> for a complete description of timing function calculation.</p>
<table class="def propdef" data-link-for-hint="animation-timing-function">
<tbody>
<tr>
<th>Name:
<td><dfn class="dfn-paneled css" data-dfn-type="property" data-export="" data-lt="animation-timing-function" id="propdef-animation-timing-function">animation-timing-function<span class="dfn-panel" data-deco=""><b><a href="#propdef-animation-timing-function">#propdef-animation-timing-function</a></b><b>Referenced in:</b><span><a href="#ref-for-propdef-animation-timing-function-1">4.
Keyframes</a></span><span><a href="#ref-for-propdef-animation-timing-function-2">4.1.
Timing functions for keyframes</a></span><span><a href="#ref-for-propdef-animation-timing-function-3">4.4.
The animation-timing-function property</a> <a href="#ref-for-propdef-animation-timing-function-4">(2)</a> <a href="#ref-for-propdef-animation-timing-function-5">(3)</a> <a href="#ref-for-propdef-animation-timing-function-6">(4)</a></span></span></dfn>
<tr class="value">
<th>Value:
<td class="prod"><a class="production css" data-link-type="type" href="#typedef-single-timing-function" id="ref-for-typedef-single-timing-function-1"><single-timing-function></a><a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-comma">#</a>
<tr>
<th>Initial:
<td>ease
<tr>
<th>Applies to:
<td>all elements, ::before and ::after pseudo-elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>interactive
<tr>
<th>Computed value:
<td>As specified
<tr>
<th>Animatable:
<td>no
<tr>
<th>Canonical order:
<td>per grammar
</table>
<p>The values and meaning of <dfn class="dfn-paneled css" data-dfn-type="type" data-export="" data-lt="<single-timing-function>" id="typedef-single-timing-function"><single-timing-function><span class="dfn-panel" data-deco=""><b><a href="#typedef-single-timing-function">#typedef-single-timing-function</a></b><b>Referenced in:</b><span><a href="#ref-for-typedef-single-timing-function-1">4.4.
The animation-timing-function property</a></span><span><a href="#ref-for-typedef-single-timing-function-2">4.10.
The animation shorthand property</a></span></span></dfn> are identical to those of <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-transitions-1/#single-transition-timing-function" title="Expands to: linear | step-start | cubic-bezier() | ease | ease-out | step-end | ease-in | ease-in-out | steps()"><single-transition-timing-function></a> <a data-link-type="biblio" href="#biblio-css3-transitions">[CSS3-TRANSITIONS]</a>.</p>
<p>The timing function specified applies to each iteration of the animation,
not the entire animation in full.
For example, if an animation has <a class="css" data-link-type="propdesc" href="#propdef-animation-timing-function" id="ref-for-propdef-animation-timing-function-5">animation-timing-function: ease-in-out; animation-iteration-count: 2;</a>,
it will ease in at the start,
ease out as it approaches the end of its first iteration,
ease in at the start of its second iteration,
and ease out again as it approaches the end of the animation.</p>
<p>When specified in a keyframe, <a class="property" data-link-type="propdesc" href="#propdef-animation-timing-function" id="ref-for-propdef-animation-timing-function-6">animation-timing-function</a> defines
the progression of the animation
between the current keyframe
and the next keyframe for the animating property
in sorted keyframe selector order
(which may be an implicit 100% keyframe).
The specified timing function
will apply over this interval
independently of the animation’s current direction.</p>
<h3 class="heading settled" data-level="4.5" id="animation-iteration-count"><span class="secno">4.5. </span><span class="content"> The <a class="property" data-link-type="propdesc" href="#propdef-animation-iteration-count" id="ref-for-propdef-animation-iteration-count-1">animation-iteration-count</a> property</span><a class="self-link" href="#animation-iteration-count"></a></h3>
<p>The <a class="property" data-link-type="propdesc" href="#propdef-animation-iteration-count" id="ref-for-propdef-animation-iteration-count-2">animation-iteration-count</a> property specifies the number of times an animation cycle
is played. The initial value is <span class="css">1</span>, meaning the animation will play from beginning to end
once. This property is often used in conj
7E1
unction with an <a class="property" data-link-type="propdesc" href="#propdef-animation-direction" id="ref-for-propdef-animation-direction-3">animation-direction</a> value of <a class="css" data-link-type="maybe" href="#valdef-animation-direction-alternate" id="ref-for-valdef-animation-direction-alternate-1">alternate</a>, which will cause the animation to play in
reverse on alternate cycles.</p>
<p>The time window during which the animation is active
(<code>duration</code> x <code>iteration-count</code>)
is known as the <dfn data-dfn-type="dfn" data-noexport="" id="active-duration">active duration<a class="self-link" href="#active-duration"></a></dfn>.</p>
<table cla
FD93
ss="def propdef" data-link-for-hint="animation-iteration-count">
<tbody>
<tr>
<th>Name:
<td><dfn class="dfn-paneled css" data-dfn-type="property" data-export="" data-lt="animation-iteration-count" id="propdef-animation-iteration-count">animation-iteration-count<span class="dfn-panel" data-deco=""><b><a href="#propdef-animation-iteration-count">#propdef-animation-iteration-count</a></b><b>Referenced in:</b><span><a href="#ref-for-propdef-animation-iteration-count-1">4.5.
The animation-iteration-count property</a> <a href="#ref-for-propdef-animation-iteration-count-2">(2)</a> <a href="#ref-for-propdef-animation-iteration-count-3">(3)</a></span><span><a href="#ref-for-propdef-animation-iteration-count-4">4.9.
The animation-fill-mode property</a> <a href="#ref-for-propdef-animation-iteration-count-5">(2)</a> <a href="#ref-for-propdef-animation-iteration-count-6">(3)</a> <a href="#ref-for-propdef-animation-iteration-count-7">(4)</a></span></span></dfn>
<tr class="value">
<th>Value:
<td class="prod"><a class="production css" data-link-type="type" href="#typedef-single-animation-iteration-count" id="ref-for-typedef-single-animation-iteration-count-1"><single-animation-iteration-count></a><a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-comma">#</a>
<tr>
<th>Initial:
<td>1
<tr>
<th>Applies to:
<td>all elements, ::before and ::after pseudo-elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>interactive
<tr>
<th>Computed value:
<td>As specified
<tr>
<th>Animatable:
<td>no
<tr>
<th>Canonical order:
<td>per grammar
</table>
<p><dfn class="dfn-paneled css" data-dfn-type="type" data-export="" data-lt="<single-animation-iteration-count>" id="typedef-single-animation-iteration-count"><single-animation-iteration-count><span class="dfn-panel" data-deco=""><b><a href="#typedef-single-animation-iteration-count">#typedef-single-animation-iteration-count</a></b><b>Referenced in:</b><span><a href="#ref-for-typedef-single-animation-iteration-count-1">4.5.
The animation-iteration-count property</a></span><span><a href="#ref-for-typedef-single-animation-iteration-count-2">4.10.
The animation shorthand property</a></span></span></dfn> = infinite | <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#number-value"><number></a></p>
<dl>
<dt><dfn class="dfn-paneled css" data-dfn-for="animation-iteration-count" data-dfn-type="value" data-export="" data-lt="infinite" id="valdef-animation-iteration-count-infinite">infinite<span class="dfn-panel" data-deco=""><b><a href="#valdef-animation-iteration-count-infinite">#valdef-animation-iteration-count-infinite</a></b><b>Referenced in:</b><span><a href="#ref-for-valdef-animation-iteration-count-infinite-1">4.5.
The animation-iteration-count property</a></span></span></dfn>
<dd> The animation will repeat forever.
<dt><dfn class="css" data-dfn-for="animation-iteration-count" data-dfn-type="value" data-export="" id="valdef-animation-iteration-count-number"><a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#number-value"><number></a><a class="self-link" href="#valdef-animation-iteration-count-number"></a></dfn>
<dd>
<p>The animation will repeat the specified number of times.
If the number is not an integer,
the animation will end partway through its last cycle.
Negative numbers are invalid. </p>
<p>A value of <span class="css">0</span> is valid and, similar to an <a class="property" data-link-type="propdesc" href="#propdef-animation-duration" id="ref-for-propdef-animation-duration-3">animation-duration</a> of <span class="css">0s</span>, causes the animation to occur instantaneously. </p>
</dl>
<p>If the animation has a duration of <span class="css">0s</span>, it will occur instantaneously for any
valid value of <a class="property" data-link-type="propdesc" href="#propdef-animation-iteration-count" id="ref-for-propdef-animation-iteration-count-3">animation-iteration-count</a>, including <a class="css" data-link-type="maybe" href="#valdef-animation-iteration-count-infinite" id="ref-for-valdef-animation-iteration-count-infinite-1">infinite</a>.</p>
<h3 class="heading settled" data-level="4.6" id="animation-direction"><span class="secno">4.6. </span><span class="content"> The <a class="property" data-link-type="propdesc" href="#propdef-animation-direction" id="ref-for-propdef-animation-direction-4">animation-direction</a> property</span><a class="self-link" href="#animation-direction"></a></h3>
<p>The <a class="property" data-link-type="propdesc" href="#propdef-animation-direction" id="ref-for-propdef-animation-direction-5">animation-direction</a> property defines whether or not the animation should play in reverse
on some or all cycles. When an animation is played in reverse the timing functions are also
reversed. For example, when played in reverse an <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-transitions-1/#valdef-transition-timing-function-ease-in">ease-in</a> animation would appear to be an <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-transitions-1/#valdef-transition-timing-function-ease-out">ease-out</a> animation.</p>
<table class="def propdef" data-link-for-hint="animation-direction">
<tbody>
<tr>
<th>Name:
<td><dfn class="dfn-paneled css" data-dfn-type="property" data-export="" data-lt="animation-direction" id="propdef-animation-direction">animation-direction<span class="dfn-panel" data-deco=""><b><a href="#propdef-animation-direction">#propdef-animation-direction</a></b><b>Referenced in:</b><span><a href="#ref-for-propdef-animation-direction-1">4.3.
The animation-duration property</a> <a href="#ref-for-propdef-animation-direction-2">(2)</a></span><span><a href="#ref-for-propdef-animation-direction-3">4.5.
The animation-iteration-count property</a></span><span><a href="#ref-for-propdef-animation-direction-4">4.6.
The animation-direction property</a> <a href="#ref-for-propdef-animation-direction-5">(2)</a></span><span><a href="#ref-for-propdef-animation-direction-6">4.9.
The animation-fill-mode property</a> <a href="#ref-for-propdef-animation-direction-7">(2)</a></span></span></dfn>
<tr class="value">
<th>Value:
<td class="prod"><a class="production css" data-link-type="type" href="#typedef-single-animation-direction" id="ref-for-typedef-single-animation-direction-1"><single-animation-direction></a><a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-comma">#</a>
<tr>
<th>Initial:
<td>normal
<tr>
<th>Applies to:
<td>all elements, ::before and ::after pseudo-elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>interactive
<tr>
<th>Computed value:
<td>As specified
<tr>
<th>Animatable:
<td>no
<tr>
<th>Canonical order:
<td>per grammar
</table>
<p><dfn class="dfn-paneled css" data-dfn-type="type" data-export="" data-lt="<single-animation-direction>" id="typedef-single-animation-direction"><single-animation-direction><span class="dfn-panel" data-deco=""><b><a href="#typedef-single-animation-direction">#typedef-single-animation-direction</a></b><b>Referenced in:</b><span><a href="#ref-for-typedef-single-animation-direction-1">4.6.
The animation-direction property</a></span><span><a href="#ref-for-typedef-single-animation-direction-2">4.10.
The animation shorthand property</a></span></span></dfn> = normal | reverse | alternate | alternate-reverse</p>
<dl>
<dt><dfn class="dfn-paneled css" data-dfn-for="animation-direction" data-dfn-type="value" data-export="" data-lt="normal" id="valdef-animation-direction-normal">normal<span class="dfn-panel" data-deco=""><b><a href="#valdef-animation-direction-normal">#valdef-animation-direction-normal</a></b><b>Referenced in:</b><span><a href="#ref-for-valdef-animation-direction-normal-1">4.9.
The animation-fill-mode property</a></span></span></dfn>
<dd> All iterations of the animation are played as specified.
<dt><dfn class="dfn-paneled css" data-dfn-for="animation-direction" data-dfn-type="value" data-export="" data-lt="reverse" id="valdef-animation-direction-reverse">reverse<span class="dfn-panel" data-deco=""><b><a href="#valdef-animation-direction-reverse">#valdef-animation-direction-reverse</a></b><b>Referenced in:</b><span><a href="#ref-for-valdef-animation-direction-reverse-1">4.9.
The animation-fill-mode property</a></span></span></dfn>
<dd> All iterations of the animation are played in the reverse direction
from the way they were specified.
<dt><dfn class="dfn-paneled css" data-dfn-for="animation-direction" data-dfn-type="value" data-export="" data-lt="alternate" id="valdef-animation-direction-alternate">alternate<span class="dfn-panel" data-deco=""><b><a href="#valdef-animation-direction-alternate">#valdef-animation-direction-alternate</a></b><b>Referenced in:</b><span><a href="#ref-for-valdef-animation-direction-alternate-1">4.5.
The animation-iteration-count property</a></span><span><a href="#ref-for-valdef-animation-direction-alternate-2">4.9.
The animation-fill-mode property</a></span></span></dfn>
<dd> The animation cycle iterations that are odd counts are played in the
normal direction, and the animation cycle iterations that are even
counts are played in a reverse direction.
<dt><dfn class="dfn-paneled css" data-dfn-for="animation-direction" data-dfn-type="value" data-export="" data-lt="alternate-reverse" id="valdef-animation-direction-alternate-reverse">alternate-reverse<span class="dfn-panel" data-deco=""><b><a href="#valdef-animation-direction-alternate-reverse">#valdef-animation-direction-alternate-reverse</a></b><b>Referenced in:</b><span><a href="#ref-for-valdef-animation-direction-alternate-reverse-1">4.9.
The animation-fill-mode property</a></span></span></dfn>
<dd> The animation cycle iterations that are odd counts are played in the
reverse direction, and the animation cycle iterations that are even
counts are played in a normal direction.
</dl>
<p class="note" role="note">Note: For the purpose of determining whether an iteration is even or odd,
iterations start counting from 1.</p>
<h3 class="heading settled" data-level="4.7" id="animation-play-state"><span class="secno">4.7. </span><span class="content"> The <a class="property" data-link-type="propdesc" href="#propdef-animation-play-state" id="ref-for-propdef-animation-play-state-1">animation-play-state</a> property</span><a class="self-link" href="#animation-play-state"></a></h3>
<p>The <a class="property" data-link-type="propdesc" href="#propdef-animation-play-state" id="ref-for-propdef-animation-play-state-2">animation-play-state</a> property defines whether the animation is running or paused.</p>
<table class="def propdef" data-link-for-hint="animation-play-state">
<tbody>
<tr>
<th>Name:
<td><dfn class="dfn-paneled css" data-dfn-type="property" data-export="" data-lt="animation-play-state" id="propdef-animation-play-state">animation-play-state<span class="dfn-panel" data-deco=""><b><a href="#propdef-animation-play-state">#propdef-animation-play-state</a></b><b>Referenced in:</b><span><a href="#ref-for-propdef-animation-play-state-1">4.7.
The animation-play-state property</a> <a href="#ref-for-propdef-animation-play-state-2">(2)</a> <a href="#ref-for-propdef-animation-play-state-3">(3)</a></span><span><a href="#ref-for-propdef-animation-play-state-4">5.2.
Types of AnimationEvent</a></span></span></dfn>
<tr class="value">
<th>Value:
<td class="prod"><a class="production css" data-link-type="type" href="#typedef-single-animation-play-state" id="ref-for-typedef-single-animation-play-state-1"><single-animation-play-state></a><a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-comma">#</a>
<tr>
<th>Initial:
<td>running
<tr>
<th>Applies to:
<td>all elements, ::before and ::after pseudo-elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>interactive
<tr>
<th>Computed value:
<td>As specified
<tr>
<th>Animatable:
<td>no
<tr>
<th>Canonical order:
<td>per grammar
</table>
<p><dfn class="dfn-paneled css" data-dfn-type="type" data-export="" data-lt="<single-animation-play-state>" id="typedef-single-animation-play-state"><single-animation-play-state><span class="dfn-panel" data-deco=""><b><a href="#typedef-single-animation-play-state">#typedef-single-animation-play-state</a></b><b>Referenced in:</b><span><a href="#ref-for-typedef-single-animation-play-state-1">4.7.
The animation-play-state property</a></span><span><a href="#ref-for-typedef-single-animation-play-state-2">4.10.
The animation shorthand property</a></span></span></dfn> = running | paused</p>