Mozilla has released the first beta versions of Firefox 4 for mobile phones.

The browser is compatible with Android-based smartphones and the Nokia N900, Mozilla said in blog.

The beta versions include a feature called Sync, which synchronises a user's tabs, history, bookmarks and passwords between the Firefox browser on a desktop PC and that on the smartphone.

The browser also comes with what Mozilla calls the Awesome Screen, which gives the user access to recent browsing history, bookmarks and tabs by tapping on the browser's address bar. The start screen shows tabs from the last time the user accessed the Internet, tabs from the PC and suggests add-ons to the browser to personalize it.

Firefox for mobile is available for the Nokia N900, or for phones running Android 2.0 or newer. It has been tested on the Nexus One, HTC's Desire and EVO 4G, and Motorola's Droid 2. The browser should work on other Android-based smartphones from Motorola and HTC, as well, including the Droid Incredible, Droid X and the Milestone, but hasn't been tested on these devices. The Samsung Galaxy S is also included in the latter group, according to a list of compatible phones on Mozilla's website.

To improve speed and responsiveness, the browser runs the user interface in a separate process from the one rendering web content. The split allows Firefox to react faster to user input while pages are loading, according to Mozilla.

The Firefox development team is keeping quiet on when the final release will be available, only saying "the Firefox 4 Beta software will update regularly so you can test new features or changes, and it will eventually update to the final release".

See also: Mozilla confirm Firefox won't be coming to the iPhone