While Mozilla has added some important mobile features, such as Sync and the Awesome Bar, the most dramatic change is under the covers. The open-source browser includes two big architectural changes, which Mozilla calls Electrolysis and Layers.
Electroysis lets the browser interface run as a separate process from the one rendering web content. The architecture makes Firefox 4 much more responsive as a mobile browser, Mozilla said.
The other big design change, Layers, involves how the browser handles graphics in regards to such functions as scrolling, pinch-to-zoom and animations. The Layers architecture allows for hardware acceleration in driving graphics-related functionality, Mozilla mobile engineer Matt Brubeck said in his blog.
The latest Firefox for mobile also contains features not found on other browsers for phones based on Google's Android operating system, Mozilla says. Those features include the ability to sync bookmarks, tabs, history, passwords and form data between the mobile browser and version of Firefox on a desktop or laptop.
Another unique feature, the Awesome Bar, launches a separate screen where users can access recent history, bookmarks and tabs.
Like the desktop browser, add-ons built by third-party developers will be available for the new mobile browser. Add-ons are an important differentiator for Firefox, because it enables users to customize the browser with a broad range of additional features.
The beta version of Firefox 4 is being offered primarily as a test drive for people interested in providing Mozilla with feedback in developing the final product. Besides Android, Firefox 4 mobile beta also is available for Maemo, a software platform developed by Nokia and used primarily in that company's smartphones. Maemo is based on the Debian Linux distribution.
But the Android platform offers Mozilla the best chance of gaining a foothold in the smartphone market. OSes from other major smartphone makers, such as Apple and Research In Motion, favor the manufacturers' proprietary browsers. In the Apple iOS found in the iPhone, it's Safari, while RIM's browser is found in the BlackBerry smartphone.
Android, on the other hand, is an open platform that's growing fast within the smartphone market. In August, 32% of people buying smartphones in the U.S. bought Android phones, versus 26% and 25% who bought BlackBerries and iPhones, respectively, according to Nielsen.
Mozilla has said that it won't build a version of Firefox for the iPhone, due to "technical and logistical restrictions" that make such a development effort nearly impossible.