I remember when I first got into this kind of stuff that you could just download a divx codec pack and put the .dlls somewhere in windows XP so that your programs could use them, why can't I do that with firefox and h.265?
Firefox doesn't use the Windows codec engine for decoding video content. I don't know why, I presume it's to keep a consistent experience (and possibly also because those codec packs used to be a major exploitation vector because they never received any security updates).
Firefox is open source, however, so there's no reason why a fork couldn't add that functionality. I personally wouldn't put any development effort into it myself and Mozilla don't seem interested, but for people who feel strongly about this there are always options.
Firefox is open source, however, so there's no reason why a fork couldn't add that functionality. I personally wouldn't put any development effort into it myself and Mozilla don't seem interested, but for people who feel strongly about this there are always options.