[kevingadd]

HTML5 video and audio in Firefox works perfectly in every site I visit. What problems do you hit? I haven't used it on Mac so perhaps the support is less good there.

Some sites don't attempt to use <video>/<audio> in Firefox for me, but that's a site issue, not a browser issue - h264 and webm both work fine.

[dbcooper]

There are a few google related ones in Karl Dubost's list:

http://www.otsukare.info/2014/10/28/google-webcompatibility-...

[Tloewald]

MP4 video support is completely absent on Mac. And MP3 audio is also not supported.