After years of throwing its weight behind Google's VP8 video codec (aka: WebM), Mozilla has officially slipped support for H.264 video into its Firefox Nightly builds -- but only for Windows 7 users. Although once a battle waged to fight costly fees and adhere to open-source principles, H.264 has since been guaranteed royalty-free while Mozilla has devised a satisfactory method for skirting around H.264's patent encumbrance.

H.264 support is now the default for users running Windows 7; however, Firefox Nightly testers have been able to turn on this feature for the past month or so by heading to about:config and setting "" to true.

During the latter part of the previous decade, the use of H.264 as the "gold standard" for HTML5-embedded video became a very contentious topic. Although H.264 is a proprietary video codec, MPEG LA (its owner) declared the codec would remain royalty-free "forever". Even so, if the group ever decided to... revise... its non-binding stance on H.264's license costs, websites, browsers and web standards could one day wake up to a nightmarish mess of legal and financial fallout -- or, at least that was the concern.

Driven by fear of H.264's commercial nature, Google became perhaps the largest proponent in the fight against H.264. It purchased the competing WebM video standard and opened it up, renaming it to VP8. Furthermore, Google vowed to remove H.264 support from Chrome -- more than two years have passed though, but the company has yet to make good this promise. H.264's widespread Internet proliferation, stellar bitrate quality and seemingly ubiquitous hardware acceleration support are just three possible reasons Google hasn't been able to let it go.

Concerned over patents and those once costly fees, Firefox, Opera and Chromium (the open-source incubator for Chrome) have continued to not support H.264. Over the years though, Mozilla seemed to be softening its position. For example, last year, Mozilla said it was considering supporting H.264 in its then-nascent mobile browser.

Because patent encumbrance is still an enormous concern for the open-source browser, Mozilla appears to be implementing H.264 at an API level instead of bundling Firefox with native support. This does present one limitation though: H.264 must be supported by the host operating system. For example, Windows 7 provides support for decoding H.264 video while Windows XP does not, which is why H.264 support is currently available only to Windows 7 users. This allows Mozilla to distribute Firefox without actually distributing MPEG LA's proprietary libraries.