On the standards track: Yes
Is Experimental: No
Is Deprecated: No
In Chrome version 74 on 2019-04-23
In Chrome Android version 74 on 2019-04-24
In Edge version 12 on 2015-07-29
In Firefox version 53 on 2017-04-19
In Firefox for Android version 53 on 2017-04-19
In Internet Explorer version 10 on 2012-10-26 Note: The ontransitionstart event handler property is not supported. To listen to this event, use element.addEventListener('transitionstart', function() {});.
In Quest Browser version 6.0 on undefined
In Opera version 62 on 2019-06-27
In Opera Android version 53 on 2019-07-11
In Safari version 13.1 on 2020-03-24 Note: The event handler exists but will never be called.
In Safari on iOS version 13.4 on 2020-03-24 Note: The event handler exists but will never be called.
In Samsung Internet version 11.0 on 2019-12-05
In WebView Android version 74 on 2019-04-24
In WebView on iOS version 13.4 on 2020-03-24 Note: The event handler exists but will never be called.