Mozilla has announced the launch of Aurora, a new Firefox release channel that is intended to open up experimental Firefox features to a broader audience of testers. The Aurora channel will serve up a stream of Firefox builds that are less fragile than the nightly builds but not as stable as official pre-releases.

Mozilla is transitioning to shorter release cycles and a more incremental development model. The organization aims to deliver three more major Firefox releases this year, bringing the open source Web browser's version number up to 7. As we explained in our previous coverage of Mozilla's 2011 roadmap, the transition will require much more intensive testing throughout the development cycle.

Mozilla has historically relied on lengthy beta test periods and a large audience of volunteer beta testers to hammer out regressions and ensure that stable releases of the browser are extremely robust. Moving to a time-based release cycle with faster iteration will obviously require more discipline and change in the approach to pre-release testing.

Launching the Aurora channel and increasing concurrent testing is one part of Mozilla's strategy for preserving its high standards of quality assurance as it transitions to shorter development cycles. As part of the transition to the channel model, Mozilla is also going eliminate the need for freezes on the mozilla-central repository during stabilization—effectively making it possible for new code to continue landing in trunk throughout the whole cycle.

Mozilla already offers a nightly build channel, which is codenamed Minefield. The Minefield builds are produced by an automated build server based on the latest Firefox code in Mozilla's version control system. Firefox contributors and some adventurous testers routinely experiment with the nightly builds and submit bug reports to Mozilla based on issues that they encounter.

The nightly builds have long been a great way to ride the burning edge of the Firefox trunk, but are subject to breakage. The quality of the nightly builds tends to fluctuate considerably throughout the development cycle. The lack of predictability makes it generally unsuitable for day-to-day use.

Mozilla is offering Aurora as a more robust alternative to nightly builds with the aim of making early-stage testing palatable to a slightly more mainstream (and much larger) audience of software enthusiasts. There will still be plenty of bugs in Aurora builds—the whole point is to expand the pool of contributors who are helping to find such bugs—but users will be able to count on it functioning from day to day without serious unexpected disruptions.

Users can expect to see updated Aurora builds issued roughly every six weeks. Mozilla will do a small amount of quality assurance prior to rolling out the updates in order to ensure basic reliability. In addition to being useful for testers and very-early adopters, the Aurora channel will also be useful to Web developers who want to experiment with implementations of the latest emerging Web standards.

The Aurora builds are available today for users to download and install. Mozilla has created specialized icons to help users visually distinguish between the various channels. I tested it on a Mac Pro, where I was able to trivially install it alongside the regular stable version of Firefox.

It basically worked as expected, but there were a few minor ruffles. It will use your default profile, which means that there might be profile issues if you are regularly switching between a stable release and Aurora builds. You might want to configure them to use separate profiles. Another issue is that the add-on compatibility checker in Aurora unsurprisingly disabled all of my add-ons. Users can install the Nightly Tester Tools add-on to override the version check.

For more details about the new channel system, you can refer to Mozilla's official blog entry or the documentation in the Mozilla Developer Center. You can download the Aurora build from the new Firefox Channels page.