On the standards track: Yes
Is Experimental: No
Is Deprecated: No
In Chrome version 1 on 2008-12-11
In Chrome Android version 18 on 2012-06-27
In Deno version 1.27 on 2022-10-27
In Edge version 12 on 2015-07-29
In Firefox version 1 on 2004-11-09 Note: Before Firefox 4, this property's value was also part of the user agent string, as reported by navigator.userAgent. Starting in Firefox 5, this property's value is based on the value of the Accept-Language HTTP header.
In Firefox for Android version 4 on 2011-03-29
In Internet Explorer version 11 on 2013-10-17 Note: Closest available (non-standard) properties are userLanguage and browserLanguage.
In Node.js version 21.2.0 on 2023-11-14
In Quest Browser version 5.0 on undefined
In Opera version 4 on 2000-06-28
In Opera Android version 10.1 on 2010-11-09
In Safari version 1 on 2003-06-23
In Safari on iOS version 1 on 2007-06-29
In Samsung Internet version 1.0 on 2013-04-27
In WebView Android version 4.4 on 2013-12-09
In WebView on iOS version 1 on 2007-06-29