Google just fired a broadside in the Web's codec wars.

With its alternative WebM video-encoding technology now entering the marketplace, Google announced plans today to remove built-in Chrome support for a widely used rival codec called H.264 favored by Apple and Microsoft. The move places Google instead firmly in the camp of browser makers Mozilla and Opera, who ardently desire basic Web technologies to be unencumbered by patent restrictions.

"Though H.264 plays an important role in video, as our goal is to enable open innovation, support for the codec will be removed and our resources directed towards completely open codec technologies," said Mike Jazayeri, a Google product manager, in a blog post.

A codec's job is to encode and decode video and audio, a technologically complicated balancing act. Codecs must reduce file sizes and enable streaming media that doesn't overtax networks, but they also must preserve as much quality as possible--for example by trying to discard data that the human senses won't miss much and cleverly interpolate to fill in the gaps.

One big change coming with the new HTML5 version of the Web page description language is built-in support for video' most Web video today employs Adobe Systems' Flash Player plug-in, which uses H.264 and other codecs under the covers. Although HTML5 video has promise, disagreements in the W3C standards group have meant the draft standard omits specifying a particular codec. Chrome was the only browser among the top five to support both WebM and H.264, but now Google has swung its vote.

Google's move triggered flabbergasted glee among advocates of the "open Web"--one that employs open standards and shuns patent barriers. "Ok this is HUGE, Chrome drops support for H264," said Mozilla developer Paul Rouget in a tweet.

But not everybody is so happy. Don MacAskill, chief executive of photo- and video-sharing site SmugMug, bemoaned the move. "Bottom line: Much more expensive to build video on the Web, and much worse user experience. And only Adobe wins," he tweeted. "I want WebM. Badly. But I need time for hardware penetration to happen...This means the cheapest way to develop video on the Web is to use Flash primarily. Before, we could do HTML5 with Flash fallback."

H.264, also called AVC, is widely supported in video cameras, Blu-ray players, and many other devices, but it comes with significant royalty licensing fees from a group called MPEG LA that licenses a pool of hundreds of video-related patents.

WebM, though, has been an open-source, royalty-free specification since Google announced it last May. It comprises the VP8 video codec Google got through its acquisition of On2 Technology and the Theora audio codec associated with an earlier and otherwise largely unsuccessful royalty-free codec effort.

It's catching on--for example with smartphone chip support from Rockchip announced last week. Hardware decoding means computing devices can decode WebM faster and without quickly sucking batteries dry. And Adobe has pledged to build VP8 support into a future version of Flash Player.

The move spotlights the role Google has earned in the Web development world by building its own browser. Chrome, which now accounts for 10 percent of browser usage worldwide, according to analytics firm Net Applications, is a vehicle Google is using to try to promote its own agenda on the Web.

One big part of that is speed--fast page loads, fast graphics, fast encryption, fast JavaScript, and more that helps expand activity on the Web. But there are plenty of cases where Google uses Chrome to advance favored standards such as WebGL for 3D graphics, Web SQL and Indexed DB for offline data storage, and WebM for HTML5 video.

Some Web developers including YouTube have begun embracing HTML5 video. But because the standard is mute on the issue of a particular codec, and because browser support can't be counted on, Web developers typically rely on Flash, which is installed on the vast majority of computers in use today.

Apple, with its own technology agenda to push, is keeping Flash off the iPhone and iPad despite Adobe's attempts to reengineer it for the low-memory, anemic-processor, battery-constrained world of smartphones. For video, those devices rely on video encoded directly with H.264.

Adobe has become a major Google ally since Apple began taking a very hard-line stance against Flash in 2010. Google has heavily promoted Adobe's mobile Flash agenda and built its Flash Player directly into Chrome. Adobe gave WebM a big boost by building it into Flash.

The partnership illustrates the pragmatic, political limits to Google's open-Web advocacy. Flash Player is proprietary software, and building it into Chrome certainly helps preserve its relevance.

"If Google is dropping H.264 because their 'goal is to enable open innovation,' why not also drop support for closed plugins like Flash" tweeted Daring Fireball Apple-watcher John Gruber.

One big uncertainty for WebM is the intellectual property purity of WebM. Google proclaimed a royalty-free codec, but that didn't stop MPEG LA from saying it's considering offering a VP8 patent pool license. "We assume virtually all codecs are based on patented technology...MPEG LA doesn't favor one codec technology over another' we are like a convenience store that offers patent licenses for any number of codecs as a service to the market," said MPEG LA Chief Executive Larry Horn last May.

More than half a year after Google released the software, though, no new pools or patent litigation has emerged, and WebM has attracted new allies. That doesn't mean litigation might not be waiting in the wings: "A codec is like a mechanical device with hundreds of parts. Any one or more could be the subject of a patent," said Steven J. Henry, an intellectual property attorney at Wolf, Greenfield & Sacks, and patent holders may wait for years before "springing the trap."

So far, that's a theoretical concern, though, and Mozilla's then-Chief Executive John Lilly said last year, "Right now we think that it's totally fine to ship, or we wouldn't ship it...We're really confident in our ability to ship this free of encumbrances."

It's possible Apple and others could embrace WebM. Microsoft has refrained from glowering too harshly on WebM even as it's issued an H.264 plug-in for Firefox users on Windows. But even if a change of heart occurs today, it will take a long time for tech giants like Apple and Microsoft to regear.

Updated 2:10 p.m. PT with further detail and commentary.