As we have previously reported, the first official Firefox 3 beta release was tentatively scheduled for late July. The beta has now been pushed back due to performance regressions and the need for extra front-end development time, and the roadmap has been altered to reflect a new release plan. According to Mike Schroepfer, Mozilla's vice president of engineering, the developers intend to issue a new pre-beta milestone release every six weeks until the program achieves beta status.

"We are driven by quality, not time. We want to Firefox 3 to be something that we are all proud of," said Schroepfer in a statement. "The Firefox front-end has had significantly less development time than the platform and has yet to have the opportunity to innovate on top of infrastructure built for places, password manager, and others. So we'd like to give them until M8 to continue to develop user-visible features on top of the core infrastructure."

A release is still scheduled for the end of the month, but it will be referred to as Alpha 7 and will not meet Mozilla's requirements for the beta designation. According to the revised roadmap, the Alpha 7 release will coincide with the Gecko feature freeze. Gecko 1.9, a long-awaited update to the HTML rendering engine used in Firefox, uses the Cairo rendering engine and features greatly improved reflow code which makes it possible for Firefox to pass the Acid2 test. The Alpha 7 release will also include finalized versions of new APIs developed for offline web applications. The next release after Alpha 7, which is currently labeled Milestone 8, is expected to ship in mid-September.

In order to meet the standards for a beta release established in the new roadmap, a milestone build has to be feature complete and stable enough for regular daily use with no significant site rendering regressions relative to the prior version. What happens when Mozilla starts releasing betas? According to Schroepfer, betas will be released regularly until benchmarks show that performance is comparable or superior to Firefox 2 with Gecko 1.8. After that release candidates will be used to resolve last minute bugs before the release.

Firefox 3 is going to be a very significant release, and a lot of work has gone into improvements under the hood so far. These delays are hardly surprising and shouldn't be perceived as a cause for concern. The new roadmap looks like a realistic adjustment to the complexity of the Firefox 3 development process, and it reflects a very clear emphasis on polish and performance.