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

The duration property of the dictionary EffectTiming in the Web Animations API specifies the duration in milliseconds that a single iteration (from beginning to end) the animation should take to complete.

Element.animate(), KeyframeEffectReadOnly(), and 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.


var timingProperties = {
  duration: durationInMilliseconds | "auto"

timingProperties.duration = durationInMilliseconds | "auto";


The number of milliseconds long a single beginning-to-end iteration of the animation should take. The default is "auto". This value must not be negative; otherwise, it can have any value (including positive infinity).

Currently, a value of "auto" is the same as specifying 0.0. This is a forwards-compatibility measure since in the future, "auto" will be expanded to take into account the duration of any child effects. Consider using "auto" rather than 0 if that makes sense.


The specified value is either a string other than "auto", a number less than zero, NaN, or some other type of object entirely.


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)"


Web Animations Level 2 (Web Animations 2)
# iteration-duration

Browser compatibility

BCD tables only load in the browser

See also