IE9 users can download the plug-in for free from You Tube owner Google's Web site. The company is warning that the software is a preview version and suffers from known issues, including freeze ups on PCs running "certain video card drivers."
Google did not specify which drivers cause the problem. The plug-in also causes video playback to halt on PCs running Sophos Antivirus. Google said Microsoft is investigating the issue.
The plug-in is necessary because IE9 does not include built-in support for WebM, an open source effort to develop an open, royalty-free video compression format that's compatible with HTML5 video. Microsoft chose instead to support H.264 video in IE9. The software maker said H.264 has a proven track record and affords better protection for content creators' intellectual property rights.
"Microsoft and other browser providers see hardware support, customer and partner readiness, and intellectual property rights as key factors making H.264 an excellent choice for video encoding and playback," said Dean Hachamovitch, Microsoft's general manager for Internet Explorer, in a blog post last year.
Google, for its part, has chosen to go with WebM, which uses the VP8 video codec and Vorbis audio streams, in its Chrome browser. Its release of a WebM plug-in for IE9, however, shows it still recognizes that Explorer continues to command the lion's share of the browser market—even though that share recently slipped below the 60% mark.
Microsoft formally launched IE9 Monday at the South by Southwest (SXSW) tech and media festival in Austin, Texas. In addition to support for hardware acceleration, it includes a number of new features, such as a slimmed-down interface and better privacy controls. With IE9, users will find a design that's less cluttered with toolbars, icons, and controls.
While most of the features from previous versions are still present, many are confined to the background as Microsoft sought to create a browser that puts more emphasis on displaying Web content rather than on its own interface.