Those Mac customers who prefer Firefox as their browser and do not have Flash installed are painfully aware that they can't view most videos they encounter. However, Mozilla has recently changed its approach, and soon we'll have H.264 support in Firefox on the Mac. It's already in Windows.
The original problem stems from the fact that Mozilla had an open web philosophy and wanted to remain unencumbered by the royalty payments required by the H.264 video codec.
Even so, viewing Internet videos on the Mac generally works because authors code a fallback option to Flash. That allows the author to avoid coding twice and takes advantage of the fact that, in OS X, most users still have Adobe Flash installed. Mozilla's Chief Technology Officer, Brendan Eich has written, "Let that sink in: we, Mozilla, rely on Flash to implement H.264 for Firefox users."
However, if one is a purist and does not have Adobe Flash installed, then clicking on a web video encoded in H.264 will look like some variation of this:
What has happened to change Mozilla's mind? It's a long and complicated technical story, and you can read more about it in the blog of Brendan Eich, Mozilla's Chief Technology Officer. The short version, for the sake of clarity here, is that 1) for several technical reasons H.264 is supported widely on mobile devices thanks to HTML5 replacing plug-ins, and 2) Microsoft is a strong supporter of H.264, likely in strategic combat against Google. Google has been developing its own royalty-free codec, WebM, but despite Google's efforts, WebM hasn't taken off.
With the popularity of H.264 as a codec to support HTML5, and the technical forces at work on the Internet, Mozilla has elected to favor its own survival and customer focus over philosophical purity and announced last year that they would be supporting H.264 on the desktop browsers. (However, Mr. Eich has stated, "We will always push for open, unencumbered standards first and foremost.")
I asked Mozilla about all this, and their spokesperson stated,
"Firefox for Android and Firefox OS already support H.264 and MP3. We are also working on bringing these formats to Firefox Desktop. On Windows 7 and above, you can already test it by turning on the preference media.windows-media-foundation.enabled in about:config. Decoding is done on the OS side (no decoder included in Firefox source code, not like WebM or Ogg Theora)."
Regarding that last part, WebM and Ogg Theora codecs are royalty-free, so Firefox can include those in the Firefox code. But as mentioned above, those codecs haven't become very popular. When H.264 is implemented, an attempt to use the OS's own decoder is made. Recently, Microsoft supplied a plug-in to allow just that.
While no timeline has been announced, the spokesperson reiterated that, "For Linux and Mac, work is in progress." If you'd like additional background, Scott Gilbertson has summed it up nicely at Webmonkey .
The net result is that because H.264 has become the most popular video codec for HTML5 and because it has become so dominant in mobile systems, we can soon expect to see Firefox supporting it on the desktop as well.
In the meantime, for those dedicated Firefox users, for H.264 encoded videos, you can either 1) install Adobe Flash for use with Firefox as the fallback, or 2) copy the URLs into Safari -- which already has the ability to decode H.264 video -- no Flash required.