The release of Firefox 3.0 has been a resounding success, but for some the upgrade path has been less than painless. The latest version of the open source browser differed enough from previous versions that many add-ons had to be substantially rewritten before they would work with the new release. And just when the dust appeared to be clearing, Firefox 3.1 is on the horizon.

Don't worry. If you weathered the transition to Firefox 3.0 (possibly with the help of some clever hacks along the way), you needn't expect a repeat performance when Firefox 3.1 arrives in late 2008 or early 2009. "In fact," says Mozilla developer Mark Finkle, "I'd go out on a limb and say updating to Firefox 3.1 will be easy."

According to Finkle in a blog post Friday, "there appear to be no plans" to introduce significant changes to the Firefox extension API in version 3.1, or to rewrite major browser components in ways similar to those that broke extension compatibility in Firefox 3.0.

Instead, he says, the major changes in the new version will be focused on bringing "serious, ass-kicking features" to the browser, most of which extend and improve existing features, rather than supplanting them. Among the proposed improvements include a reworking of the advanced bookmarking feature that debuted in Firefox 3.0, better support for audio and video out of the box, better compliance with Web standards, and performance enhancements to the rendering and JavaScript engines.

Many of the changes and new features that are planned for Firefox 3.1 were originally planned for Firefox 3.0 but couldn't be completed in time for that version's June launch date.

The first alpha release of Firefox 3.1 is expected to arrive this month. Think of that version as a developer-only release, however; it's likely to be too unstable for day-to-day use. A usable beta version will probably ship in the third quarter, and if all goes according to plan, we might even expect to see the final release by the end of this year.

To extension developers, Finkle says, "We'll make sure there are no surprises along the way."