"Firefox 15 prevents most memory leaks caused by add-ons, including Firebug," Nicholas Nethercote writes in a Mozilla blog. is a Firefox add-on for debugging web pages.

"For many users with add-ons installed, this will significantly reduce Firefox's memory consumption, without requiring upgrades to those add-ons," he adds. "For those users, Firefox 15 is likely to be faster (sometimes drastically so) and less likely to crash, especially if they have multiple add-ons installed and/or keep Firefox running for a long time between restarts."

Nethercote explains that add-on memory leaks are caused by "zombie compartments," where information from web pages is stored and remains after you close a page or depart from it.

Firefox 15 cleans out those compartments, a move that its developers weren't entirely sure would work.

Much criticism has been leveled at Firefox since its inception over its piggish memory practices, but in recent months it has made great strides in its memory management. Last , for instance, it put SpiderMonkey, the Javascript engine used by the browser, on a diet. And in , it announced its campaign to plug memory leaks in add-ons.