Analysts and reviewers have frequently pegged Firefox's extension model, where independent developers create feature add-ons, as one of its advantages over rival Internet Explorer. Mozilla, in fact, has used extensions as informal tests of features that eventually make their way into the core browser.

"We've always looked to extensions as a test bed," said Shaver. Firefox 2.0, for example, added a session restore feature that had been popularized as an extension.

"They've also provided good opportunities for other organizations to participate in the Firefox ecosystem, and [have] given smaller projects exposure," Shaver added.

According to recent data from Web metrics vendor Net Applications, Firefox accounted for 13.7% of browser usage worldwide in January, compared to 79.8% for Internet Explorer.