On the standards track: Yes
Is Experimental: No
Is Deprecated: No
In Chrome version 31 on 2013-11-12
In Chrome Android version 42 on 2015-04-15
In Edge version 12 on 2015-07-29
In Firefox version 31 on 2014-07-22 Note: Before Firefox 57, animations using em units are not affected by changes to the font-size of the animated element's parent (bug 1254424). Before Firefox 57, some language settings' inherited font-size is smaller than expected (bug 1391341).
In Firefox for Android version 31 on 2014-07-22
In Internet Explorer version 9 on 2011-03-14
In Quest Browser version 5.0 on undefined
In Opera version 28 on 2015-03-10
In Opera Android version 28 on 2015-03-10
In Safari version 7 on 2013-10-22
In Safari on iOS version 7 on 2013-09-18
In Samsung Internet version 4.0 on 2016-03-11
In WebView Android version 42 on 2015-04-15
In WebView on iOS version 7 on 2013-09-18