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 iterationStart property of the Web Animations API represents which repetition the animation begins at and its progress through it.

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


// Set the animation to start on its second iteration
var timingProperties = {
  iterationStart = 1


A whole number or decimal greater than or equal to 0.

Note: This number represents the iteration index at which the animation effect begins and its progress through that iteration. All animations' iteration indexes start at 0. Therefor a value of 0.5 would start the animation half way through its first iteration or loop. Meanwhile, a value of 1.2 indicates the animation begins 20% of the way through its second iteration.


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

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support (Yes) (Yes) 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 ? ? ? ? ? No support No support No support

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

animate() Animation Animation Timing Properties AnimationEffectTimingReadOnly.iterationStart API Experimental iterationStart KeyframeEffect() KeyframeEffectReadOnly() Property Reference waapi web animations api