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

The updatePlaybackRate() method of the Web Animations API's Animation Interface sets the speed of an animation after first synchronizing its playback position.

In some cases, an animation may run on a separate thread or process and will continue updating even while long-running JavaScript delays the main thread. In such a case, setting the playbackRate on the animation directly may cause the animation's playback position to jump since its playback position on the main thread may have drifted from the playback position where it is currently running.

updatePlaybackRate() is an asynchronous method that sets the speed of an animation after synchronizing with its current playback position, ensuring that the resulting change in speed does not produce a sharp jump. After calling updatePlaybackRate() the animation's playbackRate is not immediately updated. It will be updated once the animation's ready promise is resolved.




The new speed to set. This may be a positive number (to speed up or slow down the animation), a negative number (to make it play backwards), or zero (to effectively pause the animation).

Return value



A speed selector component would benefit from smooth updating of updatePlaybackRate(), as demonstrated below:

speedSelector.addEventListener('input', evt => {
  cartoon.ready.then(() => {
    console.log(`Playback rate set to ${cartoon.playbackRate}`);


Specification Status Comment
Web Animations
The definition of 'updatePlaybackRate()' in that specification.
Working Draft  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support No No60 No No No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support No No No60 No No No

See also

Document Tags and Contributors

Contributors to this page: chrisdavidmills, birtles
Last updated by: chrisdavidmills,