According to Mike Schroepfer, Vice President of Engineering at Mozilla, Firefox 3.1, the upcoming minor update to Firefox 3.0, delivers in certain scenarios as much as seven times more performance than its precursor. Schroepfer indicated that in terms of JavaScript, version 3.1 of the open source browser is capable of outperforming v3.0 due to the optimizations introduced in time for the Alpha 2 and Beta 1 releases. The new horsepower under-the-hood of Firefox 3.1 is generated by the evolution of the browser's SpiderMonkey JavaScript engine.

"A fantastic new improvement to Mozilla's JavaScript engine (SpiderMonkey) has landed. Code-named TraceMonkey this engine utilizes a technique, called trace trees (PDF), which adds just-in-time native code compilation to SpiderMonkey. A major goal of the project has been to set JavaScript up to compete with natively-compiled code, rather than simply against other interpreters. This means that we're starting to see speeds that are completely out of this league when it comes to performance," revealed John Resig, a JavaScript Evangelist for the Mozilla Corporation.

The addition of native code compilation to Mozilla's JavaScript engine SpiderMonkey has virtually made Firefox 3.1 fly. Mozilla's Vice President of engineering Mike Shaver indicated that over two months were spent on the evolution of SpiderMonkey. Shaver promised that Firefox 3.1 will take JavaScript performance to the next level compared to Firefox 3.0, which delivered a boost of over three times compared to version 2.0 of the open source browser. Mozilla is currently cooking the Alpha 2 release of the next iteration of Firefox with Beta 1planned for September 2008.

On August 21 "we landed TraceMonkey in the Firefox 3.1 development tree, configured off by default. We have bugs to fix, and an enormous number of optimizations still to choose from, but we're charging full speed ahead on the work we need to do for this to be a part of Firefox 3.1. Depending on the benchmarks you choose, you might see massive speed-up, minor speed-up, or maybe even some slowdown - those latter cases are definitely bugs, and reporting them through bugzilla will be a big help," Shaver stated.

Firefox 3.1 Alpha 1 for Windows is available for download here.
Firefox 3.1 Alpha 1 for Linux is available for download here.
Firefox 3.1 Alpha 1 for Mac OS X is available for download here.