The final version of Firebug 1.2 has been released and will be up on the Mozilla Add-ons site today, and it is immediately available GetFirebug.com. There have been several improvements and a huge number of bug fixes made. Some of the major features in the release include Firefox 3 support, quality improvements, selective panel enablement, and the ability to suspend/resume Firebug. Firebug 1.3 development is already underway and is going to be focused on performance, quality, and testing. John Resig writes, “Firebug is the de facto tool for web developers and we need to make sure that its quality does not wane and that we tackle performance head-on.” For more information, see John’s blog post announcing the release.

Mike Shaver writes, “Over the past year, JavaScript performance on the Web has undergone a striking revolution. Virtually every browser has improved its engine to produce significant gains in execution speed; Firefox 3 is about 3 times faster than Firefox 2 in various JavaScript benchmarks, for example. We’re not done. In addition to continuing to work on our existing JavaScript interpreter, we’re also looking farther into the future of JS performance. Yesterday we landed TraceMonkey in the Firefox 3.1 development tree, configured off by default. We have bugs to fix, and 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 part of Firefox 3.1″. Early tests are showing significant speed and performance improvements, and all of this has been blogged about at length by the various people involved:

• TraceMonkey: JavaScript Lightspeed (Brendan Eich)
• Tracing the Web (Andreas Gal)
• The Birth of a Faster Monkey (Mike Shaver)
• Great performance improvements coming for Firefox 3.1 (Mike Schroepfer)
• TraceMonkey (John Resig)