Mozilla updates Firefox 3.1 with Alpha 2 build

Computerworld - Mozilla Corp. on Friday launched the second alpha of Firefox 3.1, adding new video support and boosting the speed of some JavaScript computations.

Firefox 3.1 Alpha 2, code-named "Shiretoko," will be the last in a short series of alpha editions; Mozilla has set a late September code freeze for Beta 1 and will presumably deliver the first preview for the general public next month.

Mozilla added support for the new video element to Alpha 2 and the opening round of what's called "Web worker threads," it also enhanced the browser's performance and enabled drag-and-drop of tabs between windows.

Support for the video tag, part of the HTML 5 standard, has been pitched by developers as a way to ditch proprietary formats, including the popular Flash, and let site designers embed video directly into pages and then manipulate and control the video with scripting.

Mozilla is playing catch-up here with Apple Inc.'s Safari, which already supports the tag. Other browsers, however, including Google Inc.'s new Chrome and Microsoft Corp.'s Internet Explorer 8 Beta 2, have yet to offer support for the element.

Also in Alpha 2 is initial support for "Web worker threads," enhanced scripting functionality that lets site developers shift JavaScript computations to a background thread where they don't hit the performance of the Firefox user interface.

"The user interface will remain responsive while the [JavaScript] engine churns, and navigating away from the page will even pause its execution," Mozilla said in supporting documents about worker threads.

Other additions and changes to Firefox 3.1 showing up for the first time include: support for between-windows drag-and-drop; new support for several CSS (cascading style sheets) 2.1 and CSS 3 properties; and improved performance when viewing images with embedded color profiles.

Mozilla did not include its new TraceMonkey JavaScript interpreter in Alpha 2, however. The engine, which Mozilla recently said executes JavaScript as much as 28% faster than Chrome, will continue to be available only in Firefox 3.1 nightly builds, the dailies that Mozilla posts for its own developers. Instructions for turning TraceMonkey on in a nightly build can be found here.

Firefox 3.1 has been touted as a fast-track update to June's version 3.0; that edition worked its way through eight alphas altogether.

Mozilla has declined to set a hard deadline for the browser, saying only that it is shooting for a late 2008 or early 2009 release. Last week, however, the open-source developer pushed back Firefox 3.1 Beta 1's schedule by three weeks.

Alpha 2 can be downloaded from Mozilla's site in versions for Windows, Mac OS X and Linux.