Agreed. MP4 doesn't work on Firefox (out of the box).

You should probably qualify that somehow, because MP4 works for me on Firefox (on OSX 10.9).

It does not work for me, too. FF30, OSX 10.9.3.

https://www.evernote.com/shard/s19/sh/e81e070a-4e2e-4367-9eb...

OSX 10.9.2 + FF30 here: http://i.imgur.com/uTlQkg7.jpg

Right click the video. It's probably Flash. Plays using Flash in Firefox on my machine.

OS X is the last platform where Firefox doesn't support H.264. They're working on it, but it doesn't seem to be landing soon.

If you have a H.264 decoder installed (and most computers do), new-ish versions of Firefox will try to use it to play embedded H.264 videos. Unfortunately, a lot of sites are still in "Firefox == Flash" mode and automatically serve up the Flash version to Fx users without even trying a <video> tag.

MP4 works out of the box on my Firefox (latest stable).