On the standards track: Yes
Is Experimental: No
Is Deprecated: No
In Chrome version 42 on 2015-04-14 Note: Client objects returned in most recent focus order.
In Chrome Android version 42 on 2015-04-15 Note: Client objects returned in most recent focus order.
In Edge version 17 on 2018-04-30 Note: Client objects returned in most recent focus order.
In Firefox version 54 on 2017-06-13 Note: Before Firefox 54, Client objects were not returned in the most recent focus order as required by the specification.
In Firefox for Android version 54 on 2017-06-13 Note: Before Firefox for Android 54, Client objects were not returned in the most recent focus order as required by the specification.
Not in Internet Explorer
In Quest Browser version 5.0 on undefined Note: Client objects returned in most recent focus order.
In Opera version 29 on 2015-04-28
In Opera Android version 29 on 2015-04-28
In Safari version 11.1 on 2018-04-12
In Safari on iOS version 11.3 on 2018-03-29
In Samsung Internet version 4.0 on 2016-03-11 Note: Client objects returned in most recent focus order.
In WebView Android version 42 on 2015-04-15 Note: Client objects returned in most recent focus order.
Not in WebView on iOS