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This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The direction property of the Web Animations API dictionary AnimationEffectTimingProperties indicates an animation's playback direction along its timeline, as well as its behavior when it reaches the end of an interation

Element.animate(), KeyframeEffectReadOnly(), and KeyframeEffect() all accept an object of timing properties including direction. The value of direction corresponds directly to AnimationEffectTimingReadOnly.direction in timing objects returned by AnimationEffectReadOnly, KeyframeEffectReadOnly, and KeyframeEffect.


var timingProperties = {
  direction: "normal" | "reverse" | "alternate" | "alternate-reverse"

timingProperties.direction = "normal" | "reverse" | "alternate" | "alternate-reverse";


A DOMString which specifies the direction in which the animation should play as well as what to do when the playback reaches the end of the animation sequence in the current direction. It can take one of the following values, with the default being "normal":

The animation runs forwards, from beginning to end, in the way we experience the flow of time.
The animation runs backwards, or "rewinds."
The animation switches direction after each iteration, going forward through the animation sequence the first iteration, then backward through the sequence the second iteration, and so forth.
Similar to "alternate", except the animation playback starts by going from the end of the animation sequence toward the beginning the first iteration, then goes forward during the second, and so forth.


In the Forgotten Key example, Alice waves her arm up and down by passing her an alternate value for her direction property:

// Get Alice's arm, and wave it up and down
  { transform: 'rotate(10deg)' }, 
  { transform: 'rotate(-40deg)' }
], {
  easing: 'steps(2, end)',
  iterations: Infinity,
  direction: 'alternate',
  duration: 600


Specification Status Comment
Web Animations
The definition of 'direction' in that specification.
Working Draft Editor's draft.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support (Yes) 48 (48)[1] No support (Yes) No support
Feature Android Android Webview Chrome for Android Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile
Basic support ? ? ? 48.0 (48)[1] ? No support No support No support

[1] The Web Animations API is only enabled by default in Firefox Developer Edition and Nightly builds. You can enable it in beta and release builds by setting the preference dom.animations-api.core.enabled to true, and can disable it in any Firefox version by setting this preference to false.

See also