Firefox 11 Memory Leak

I have always been a fan of Firefox and encouraged other developers to use it, addons such as Firebug and YSlow are simply essential tools for anything more than your most basic web page, and will even help with those. Neither the developer tools in Chrome, Safari or IE can really compete.

There certainly does seem to be an issue with the latest version of Firefox though regarding memory management, I am constantly seeing usage spiral up to around and over the 1GB value and become clunky and slow to respond. It looks like there is some effort going on at Mozilla to catch the culprits generally suspected to be certain addons, but personally I only used a few and still see the problem. I am looking at running some tests of my own to try and establish what is causing the issue. Firefox has been top of my toolbox for quite some time and it needs to stay that way.

Update:06-04-12 – Testing change to “Browser.sessionhistory.max”
Apparently Firefox defaults to storing 8 pages of history for each Tab that is open. This can be adjusted by setting “Browser.sessionhistory.max”
URL: about:config
Setting: Browser.sessionhistory.max
Default value is -1

Testing value set to 3.

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  • James


    If you ever find a solution to what is causing it to leak, please let me know. I am using FF11 with adblock plus, and the web developer addon. It grows to around 3.5gb of usage and then either hangs or crashes.

    I have not as yet found a solution

  • Jack Abrahams

    Even without ANY addons the leak is still present … so it’s not necessarily the addons that are at fault but the base browser. I love firefox but the memory leak needs fixing before I go back to it from now using Chrome.

    • Simon

      It’s never been as bad is it seems right now. Starting to hinder development having to restart Firefox every so often and even then it seems to take time to kill the windows process before I can relaunch it (unless I manually kill the process).

      I am currently trying a change to Browser.sessionhistory.max which initially does seem to be helping – see update in post, but nothing conclusive.

  • shadow_man

    Are these memory leaks only in windows 7? I’m using windows xp and firefox 11 only takes around 110k memory and have never seen a leak so far.

    • Simon

      I am using Win 7, have not tried on other O/S’s.

      Setting ‘Browser.sessionhistory.max’ has definitely helped (although not completely resolved) the problem for me.

  • Milo

    I have Firefox 11 on my Mac. It gradually used all the available ram until it was using 2.6 GB, split fairly evenly between Firefox and the Flash plugin.
    Just updated to Firefox 12. Hope this is fixed now!

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