In our latest browser speed tests, I half-heartedly complained that Firefox eats up memory over long periods of use. Our lovely, helpful commenters pointed out that there is, indeed, a tweak to help with that.


It's important to note that this about:config tweak doesn't actually change how Firefox uses (and hoards) memory over actual use. For the purposes of user speed, then, it's not much change. But while Windows can normally grab memory back from applications that are minimized, Firefox prevents that and keeps all the memory it acquired during your multi-tab wanderings—unless you enable this tweak, which some have claimed also makes Firefox scale down the big memory pile it had going upon re-focusing.


Let's get started. Type about:config into your address bar, hit Enter, and confirm to your browser that you'll be careful messing with your configuration. Unless you've performed this specific change before, right-click somewhere outside all those period-separated values and choose New/Boolean. In the window that pops up, enter config.trim_on_minimize and hit OK, then select "True" in the next dialog. Close out your about:config window, restart Firefox, and you're now demanding that Firefox give up some of that sweet, sweet RAM when it's not even showing on your desktop.

This could lead, of course, to slower functionality when re-maximizing Firefox, or even bugginess. And those who are using Firefox just fine with its standard memory settings should probably leave well enough alone. You can read up on just what this trick does at the MozillaZine Knowledge Base. Need to undo it? Simply head back to about:config , start typing in the boolean variable's name again ( config.trim_on_minimize ), and when it pops up, switch it back to "False" by double-clicking or right-clicking.

Have you used this little Firefox tweak to save memory and stuck with it? Finding it buggy and unreliable? Post your impressions and details in the comments.


Thanks to alejo0121 for pointing out this trick, and to our own Asian Angel and Gina Trapani for confirming its validity.