Mozilla is outspoken in its dislike of the patent-encumbered video technology called H.264, but Microsoft, an H.264 fan, is providing a plug-in that will let Windows 7 users use it anyway.

H.264 is a codec--technology to encode and decode video--that's widely used in videocameras, Blu-ray players, online video streaming, and more. It's built into Adobe Systems' Flash Player browser plug-in, but most people don't know or need to know it's there.

When it comes to the flagship feature of built-in video support coming to the new HTML5 specification for creating Web pages, though, codec details do matter. Not all browsers support H.264 or its open-source, royalty-free rival from Google, the VP8-based WebM. That means Web developers must make sure they support both formats or provide a fallback to something like Flash. Otherwise they risk leaving some viewers behind.

To help bridge the divide, Microsoft has released a plug-in that lets Firefox tap into Windows 7's native H.264 support for HTML5 video. The move could help pave over some of the new Web's rough patches, but also irritate WebM fans who want to see the Web move to unencumbered technology.

"H.264 is a widely-used industry standard, with broad and strong hardware support. This standardization allows users to easily take what they've recorded on a typical consumer video camera, put it on the Web, and have it play in a web browser on any operating system or device with H.264 support, such as on a PC with Windows 7," Microsoft said. "The HTML5 Extension for Windows Media Player Firefox Plug-in continues to offer our customers value and choice, since those who have Windows 7 and are using Firefox will now be able to watch H.264 content through the plug-in."

According to the plug-in's release notes, "The extension is based on a Firefox add-on that parses HTML5 pages and replaces video tags with a call to the Windows Media Player plug-in so that the content can be played in the browser. The add-on replaces video tags only if the video formats specified in the tag are among those supported by Windows Media Player. Tags that contain other video formats are not touched." Microsoft is working on ironing out user-interface differences between Windows Media Player controls and those that would show with video playing natively in the browser.

Microsoft already had offered a related Firefox plug-in that let people watch Windows Media videos on the Web.

Mozilla is working to try to establish WebM as a required codec for HTML5, a specification standardized by the World Wide Web Consortium (W3C).

Updated 8:37 a.m. PT with download link and release note information.