Firefox 3.5 Nears Completion, Beta 4 Now Available

Mozilla has released a fourth beta of the next version of its Firefox web browser. Firefox 3.5 beta 4 is expected to be the last beta release for this latest version of Firefox, with the final code due to arrive in a couple of months.

Earlier betas in this round of experimental Firefox builds were labeled 3.1, and the browser was expected to be released at the end of 2008. However, Mozilla decided to push the release date well into 2009 and the company bumped the version number to 3.5 after deciding that the new features were more significant than it had originally envisioned. These new features include an enhanced JavaScript rendering engine to speed up web apps, an improved session restore tool and a private browsing mode (commonly known as “porn mode”) that eschews local page caching on a per-session basis. These were added largely in response to similar features that popped up in Google Chrome and Microsoft Internet Explorer 8, both of which were released while the latest Firefox was still in the early development stages.

Firefox 3.5 beta 4 primarily brings stability improvements, bug fixes and some more speed gains, particularly in the new TraceMonkey JavaScript Engine. If you’ve been following along and testing earlier beta releases, there won’t be any significant new features in this release, just improvements.

One noteworthy addition not found in beta 3 is the “Recently Closed Windows” tool, which works much like the “Recently Closed Tabs” tool by allowing you to re-open entire windows you’ve accidentally closed.

For more details on the other new features in Firefox 3.5, check out our earlier coverage, and be sure to read through the latest release notes before you download beta 4 (it is a beta and there are some known bugs). In our testing, we haven’t noticed any major problems.

One word of warning for those itching to get their hands on beta 4 — don’t expect all of your extensions to work just yet. If you’re a heavy extensions user, you may want to hold off upgrading until your must-haves have been updated. Most extension providers don’t bother building in support for new versions of Firefox until the browser reaches the release candidate stage.