Mozilla is adding support for existing wide-spread -webkit-prefixed properties for compatibility reasons[0][1].<p>Existing properties which Webkit <i>isn&#x27;t dropping</i>, they&#x27;re dropping prefixes for <i>new experimental features</i>, a move Firefox (and Chrome) made more than 3 years ago.<p>Which you&#x27;d have know had you read the first comment of the sister story instead of going no further than the story title.<p>[0] <a href="https:&#x2F;&#x2F;compat.spec.whatwg.org&#x2F;#introduction" rel="nofollow">https:&#x2F;&#x2F;compat.spec.whatwg.org&#x2F;#introduction</a><p>[1] following the lead of Opera and Microsoft in doing so