Mozilla claims that the upcoming Firefox 15 web browser automatically closes memory leaks caused by add-ons.

In the beta version of Firefox 15, the Mozilla developers force add-ons to release memory allocated to them. Mozilla's developers claim that many add-ons are causing memory leaks by not releasing their DOM structures when a tab is closed. This creates what the developers call zombie compartments - areas of memory that are never released.

Since individual tabs use their own privileged memory compartments, add-ons have to reference memory addresses in those tab compartments to interact with web sites. These references are then recorded in a list. The changes in Firefox 15 make sure that this list is checked when tabs are being closed or new pages are loaded. Superfluous DOM references can then be deleted based on this check.

Mozilla's in-house testing showed that Firefox 15 beta prevents the vast majority of leaks that occur in existing add-ons.

High memory consumption particularly on long browsing sessions has been always been a headache for Mozilla.

During testing with the memory hog SiteAdvisor 3.1.4, the developers apparently detected 1.4 to 1.7GB of memory being released when closing 150 tabs - the previous version of Firefox had only freed 200MB.

From version 17, Firefox developers are planning to cut down even more on memory usage by also deleting sandboxes which are not being used.

Firefox 15 Beta for Android has also been released. This version has been optimised for tablets, but according to the release notes, it still has some bugs and should be used for testing purposes only.