Keyframe Formats

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

Element.animate(), KeyframeEffectReadOnly.KeyframeEffectReadOnly(), KeyframeEffect.KeyframeEffect(), and KeyframeEffect.setKeyframes() all accept objects formatted to represent a set of keyframes. There are several options to this format, which are explained below.


There are two different ways to format keyframes:

  1. An object containing key-value pairs consisting of the property to animate and an array of values to iterate over.

      opacity: [ 0, 1 ],          // [ from, to ]
      color:   [ "#fff", "#000" ] // [ from, to ]
    }, 2000);
  2. An array of objects (keyframes) consisting of properties and values to iterate over. This is the canonical format returned by the getKeyframes() method.

      { // from
        opacity: 0,
        color: "#fff"
      { // to
        opacity: 1,
     ​   color: "#000"
    ], 2000);

    With this latter form it is also possible to specify offsets for each keyframe by providing an offset value.

    element.animate([ { opacity: 1 },
                      { opacity: 0.1, offset: 0.7 },
                      { opacity: 0 } ],

    Note: offset values, if provided, must be between 0.0 and 1.0 and arranged in ascending order.

    Furthermore, using this form it is also possible to specify easing to apply between keyframes by providing an easing value as illustrated below.

    element.animate([ { opacity: 1, easing: 'ease-out' },
                      { opacity: 0.1, easing: 'ease-in' },
                      { opacity: 0 } ],

    In this example, the specified easing only applies from the keyframe where it is specified until the next keyframe. Any easing value specified on the options argument, however, applies across a single iteration of the animation — for the entire duration.



You can specify as many property value pairs as are contained in each keyframe of the animation. Each property value pairs support the standard CSS properties, but also the following additional attributes:


The offset of the keyframe specified as a number between 0.0 and 1.0 inclusive or null. This is equivalent to specifying start and end states in percentages in CSS stylesheets using @keyframes. This will be null if the keyframe is automatically spaced using KeyframeEffect.spacing.


The computed offset for this keyframe, calculated when the list of computed keyframes was produced according to KeyframeEffect.spacing. Unlike offset, above, the computedOffset is never null.


The timing function used from this keyframe until the next keyframe in the series.


The KeyframeEffectReadOnly.composite operation used to combine the values specified in this keyframe with the underlying value. This will be absent if the composite operation specified on the effect is being used.




Specification Status Comment
Web Animations
The definition of 'Keyframe object formats' in that specification.
Working Draft Initial definition

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support No support (Yes) No support No support No support
Feature Android Android Webview Chrome for Android Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile
Basic support ? ? ? ? ? No support No support No support

See also

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