This release candidate represents what the development team feels is a finished browser, said Johnathan Nightingale, director of Firefox development, in an interview.
The quality assurance team will still take feedback from users over the next few weeks, but if no major bugs are found, Mozilla expects to issue the full production release of the browser by the end of the month, he said.
If so, March will be a busy month for the ongoing browser wars. In addition to the pending final release of Firefox 4, Microsoft plans to launch version 9 of its Internet Explorer on March 14. And Google released version 10 of its Chrome browser on Monday.
Version 4 of Firefox is a major upgrade for the open-source browser, and includes a wealth of new features and enhancements.
Tab management has also taken a great leap forward. Users can bundle sets of tabs into different groups, under a feature called Panorama. They can add small permanent tabs to the top of the browser, for those pages and applications they continually keep open.
For the first time, Firefox will allow users to synchronize their bookmarks across different computers and even with Android-based mobile phones. This is also the first version of the browser to include the Do Not Track feature, which can alert website owners if the user wishes to opt out of third-party Web tracking.
The release candidate is available for the Windows, Mac and Linux platforms, and supports more than 70 languages. Current users of the beta version will have their browsers automatically updated.