If you've been using the Firefox 3.5 beta, you now get to upgrade to the release candidate for Firefox 3.5. Available for Windows, Mac, and Linux, The noticeable changes to the release candidate from beta 4 and the b99 pre-release version are not readily apparent. Generally, you can expect the release candidate to be more stable than its beta predecessors, although if you're using an add-on such as Nightly Tester Tools or MR Tech to force incompatible add-ons to work in the beta you may be compromising your stability somewhat.

Firefox 3.5 natively supports HTML5 and embedded Ogg video content. (Credit: Screenshot by Seth Rosenblatt/CNET)

The upgrades to Firefox 3.5 have been well-documented by now. Private browsing, geolocation, faster performance than Firefox 3 for both loading pages and running JavaScript, local storage for better offline support, and native video for Ogg/Vorbis. If you're running the release candidate or one of its beta predecessors, you can check out Daily Motion to see how the non-Flash based video playback performs.

More improvements include support for HTML5 tags such as and , native JSON support, support for Web workers so browser-based apps can run in the background, support for CSS and SVG standards, the ability to erase browsing traces by site or by time, personas for easier theme management, and downloadable fonts. The release candidate is also available in more than 70 language localizations.

Because of the 800,000 or so testers that Mozilla says have been using the beta versions, Firefox director Mike Beltzner said that he expects this to be the sole release candidate before version 3.5 goes public at the end of June.

Annoyingly, Firefox 3.5 RC1 doesn't list itself as a release candidate in the program's About box, but in half a day of testing no problems have arisen.