Mozilla delivers Firefox 3.5 Beta 4, boosts speed

Mozilla Corp. late yesterday released Firefox 3.5 Beta 4, the latest development preview of the company's next browser, which has been delayed several times and now is tentatively slated to ship before the end of June.

The milestone features more work under the hood — particularly in stability and performance of the new TraceMonkey JavaScript engine — as well as tweaks to the private browsing mode and improvements to the underlying Gecko layout engine, said Mike Beltzner, director of Firefox.

Computerworld's tests showed that Firefox 3.5 Beta 4 is about 19% faster than Beta 4 in the SunSpider JavaScript benchmark; both betas were considerably faster than the production browser, Firefox 3.0.10, which was also released yesterday.

Other enhancements, said Beltzner in a message posted to the mozilla.dev.planning forum, have been made to Firefox's new location awareness feature, and support for Web worker threads — an enhanced scripting functionality that lets site developers shift JavaScript computations to a background thread — has been completed.

As it usually does, Mozilla warned users that Beta 4 is suitable for testing only. “Firefox 3.5 Beta 4 is a public preview release intended for developer testing and community feedback,” said Beltzner. We recommend that you read the release notes and known issues before installing this beta.”

The beta's release notes highlighted several still-unfixed issues with Firefox 3.5, including problems with Gmail, Google Inc.'s popular Web-based e-mail service, and with parts of the new privacy feature.

Beta 4 is the first major milestone of Mozilla's new browser to carry the “3.5” moniker; originally, the upgrade was called Firefox 3.1, but the company decided it had added enough new features to justify the larger bump in version number from last summer's Firefox 3.0.

Those additional features — especially TraceMonkey — caused some delays last year as Mozilla worked to both integrate the new JavaScript engine and test it. Other delays were the result of troublesome bugs, many of them also in TraceMonkey.

Although Mozilla said much earlier in the Firefox 3.5 process that it would ship a limited number of betas before moving on to a “release candidate,” it's unclear today what Mozilla's next step will be. Attempts to reach Beltzner via e-mail were unsuccessful.

In 2008, the company issued the last beta of Firefox 3.0 in early April, and the final version in mid-June. Assuming Firefox 3.5's pace is similar, Mozilla should ship Firefox 3.5 sometime in early July.

Firefox 3.5 Beta 4 can be downloaded for Windows, Mac OS X and Linux in 63 different languages from Mozilla's site. Users already running Beta 3 will be notified of the available update in the next 48 hours.