Google Chrome Frame is an Internet Explorer plugin which installs Chrome's WebKit and V8 rendering engines alongside Internet Explorer's own Trident. By adding a special meta tag to their web pages, web developers can tell Internet Explorer to switch to Chrome Frame instead of Trident. It is used by some popular web sites, like Google Wave, Meebo, and YouTube.
Google Chrome Frame was initially released as a developer preview in September 2009 (much to Microsoft's chagrin), and has now moved it into beta. A whole boatload of bugs ave been fixed, and several HTML5 features have been added as well, bringing the beta on-par with its big brother Chrome 5.0.
"Since our initial launch, we've been listening to developers: instead of adding new bells and whistles, we've fixed more than 200 bugs to make integration with Internet Explorer seamless while improving security, stability, and performance," write Amit Joshi and Alex Russell, software engineers at Google, "For example, we've improved our handling of Internet Explorer's InPrivate browsing, cache clearing, and cookie blocking. All of the enhancements and features of Google Chrome 5.0 are available in Google Chrome Frame too, including HTML5 audio and video, canvas, geolocation, workers, and databases."
Users who already had Chrome Frame installed will get the update to the beta automatically, and those that do not yet have it can download it today. If you want to remain on the bleeding edge of Chrome Frame development, you can subscribe to the developer channel as well. Frame works with Internet Explorer 6, 7, and 8, on Windows XP SP2, Vista, and 7.
For web developers who want to make use of Chrome Frame, the documentation is a good place to start.