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 Animation.startTime property of the Animation interface returns or sets the scheduled time when an animation's playback should begin. 

An animation’s start time is the time value of its DocumentTimeline when its target KeyframeEffect is scheduled to begin playback. An animation’s start time is initially unresolved.


// getting an animation's startTime
var animationStartedWhen = animation.startTime;

// setting an animation's startTime
animation.startTime = 300;


A number representing the current time in milliseconds, or null.


In the Running on Web Animations API example, the we can sync all new animated cats by giving them all the same startTime as the original running cat:

var catRunning = document.getElementById ("withWAAPI").animate(keyframes, timing);

/* A function that makes new cats. */
function addCat(){
  var newCat = document.createElement("div");
  return newCat;

/* This is the function that adds a cat to the WAAPI column */
function animateNewCatWithWAAPI() {

  // make a new cat
  var newCat = addCat();

  // animate said cat with the WAAPI's "animate" function
  var newAnimationPlayer = newCat.animate(keyframes, timing);

  // set the animation's start time to be the same as the original .cat#withWAAPI
  newAnimationPlayer.startTime = catRunning.startTime;

  // Add the cat to the pile.


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

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 39.0 48 (48) No support No support No support
Feature Android Android Webview Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile Chrome for Android
Basic support No support 39.0 48.0 (48) No support No support No support 39.0


See also


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

Animation API Experimental Expérimental Interface Property Reference startTime Web Animations