Mozilla will relaunch its popular Firefox add-on site this week by culling the several thousand extensions listed for its open-source browser to just a couple of hundred.

The move is part of a general overhaul of the add-on site, which will also feature more support for international users and new tools for user-to-user discussions.

But it's the thinning of the add-on herd that may raise eyebrows. "We're trying to tighten up the extensions, especially for new first-time users," said Mike Shaver, Mozilla's technology strategist.

Rather than list all the available Firefox and Thunderbird extensions -- Shaver estimated that there are approximately 2,000 available now -- the site will drop marginal add-ons, as well as those no longer maintained by their creator or not updated for the browsers and e-mail clients now in use. A couple of hundred extensions will remain on the site after Monday.

That list will change, said Shaver, because users will be able to nominate untried or niche extensions for promotion from what he called a "sandbox."

"Some extensions will be in the sandbox for a while, some will be moved to the public site," said Shaver. The idea is to make it easier for users, particularly new Firefox users, to find the most worthwhile and useful add-ons for the browser.

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.