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 duration property of the Web Animations API represents the duration in milliseconds to complete a single iteration of the animation.

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


// how long each loop should last
var timingProperties = {
  duration: 250


The number of milliseconds each iteration of the animation takes to complete. Defaults to 0.

Note: In this level of this specification, the string value auto is equivalent to 0. This is a forwards-compatiblity measure since a future level of this specification will introduce group effects where the auto value expands to include the duration of the child effects.


In the Pool of Tears example, each tear is passed a random duration via its timing object:

// Randomizer function
var getRandomMsRange = function(min, max) {
  return Math.random() * (max - min) + min;

// Loop through each tear
tears.forEach(function(el) { 

  // Animate each tear
       delay: getRandomMsRange(-1000, 1000), // randomized for each tear
       duration: getRandomMsRange(2000, 6000), // randomized for each tear
       iterations: Infinity,
       easing: "cubic-bezier(0.6, 0.04, 0.98, 0.335)"


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

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support (Yes) 48 (48) 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