Prevent Firefox From Hogging Memory When Minimised

Prevent Firefox From Hogging Memory When Minimised

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 minimised, 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-maximising 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 founding editor Gina Trapani for confirming its validity.


  • im not sure why people are so worried about memory usage of a browser…7 years ago yes it was only an occasionally used software package…..but nowadays its the MAIN application on any computer, and performs so many tasks for people now

  • I mostly use Opera because I can have -lots- of Web pages open with relatively little memory taken per page – I don’t have a lot of memory on my UMPC (

  • WHY WORRY ABOUT MEMORY USAGE? How about because when I return to my computer after 5+ hours of idling firefox (The memory gluten) has consumed and failed to release 1.6GB of my fucking ram!? Also, -for the record- 7 years ago the average computer didn’t have a gig of ram in them for a user to bitch about having so much used by their browser.

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