How to Stop a Firefox Memory Leak

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Burnin firefoxFirefox is our browser of choice. It’s fast, stable, and developer friendly. It has tons of useful plugins and themes (skins) you can use to customize and make Firefox your own. The only problem is that amidst the excitement of adding all these cool plugins, you won’t realize the incredible amount of memory that Firefox will begin sucking from your system. The result? Slower loading web pages, a slower PC, slower everything. Fortunately, there’s a couple of steps you can take to get Firefox back on the fast track.

Steps to Halt A Firefox Memory Leak

There are some basic steps you can take to help reduce memory leakage in Firefox. These are:

  • Upgrade Firefox. Newer versions of Firefox use less memory by containing memory leaks more efficiently.
  • Disable unnecessary plugins and add-ons, and extensions (open your “Add-Ons manager” and shut down any you think you don’t need. You can always re-enable them if it turns out you do). This is by far the biggest memory saver. If Firefox is your primary browser, you might also consider using another browser for the add-ons you only use occasionally (for example, Java).
  • Reduce misuse by malicious sites by running a spam or antivirus blocker on a regular basis. We recommend the free Spybot Search & Destroy to get you started.
  • Keep your number of open tabs and windows to a minimum.
  • Type “about:config” in your browser bar and adjust the following preferences (by double clicking on them) to free up some additional memory:
    • browser.cache.memory.capacity (set to 0)
    • browser.cache.memory.enable (set to false)
    • browser.sessionhistory.max_total_viewers (set to 0)
    • browser.tabs.animate (disable)
    • browser.sessionstore.max_concurrent_tabs (set to 0)
  • Here some more advanced settings to speed up page loading:
    • (set to true)
    • javascript.options.jit.content (set to true)
    • content.notify.backoffcount (set to 5)
    • network.dns.disableIPv6 (set to true)
    • network.http.pipelining (set to true)
    • network.http.proxy.pipelining (set to true)
    • network.http.pipelining.maxrequests (set to 8 )
    • plugin.expose_full_path (set to true)
    • ui.submenuDelay (set to 0)
  • When installing extensions, you can kill the default countdown (delay) by setting the following value:
    • security.dialog_enable_delay (set to 0)
  • If you have antivirus installed (Windows only), you can disable Firefox’s native virus scanner:
    • (set to false)
  • Consider installing the Ramback extension (Firefox 3.x+).
  • Windows O/S tips: Turn on virtual memory or increase the size of your paging file.

Also note that the more powerful your computer, the more memory Firefox will use. Benchmarking your Firefox memory compared to other PC’s based on the number of Windows or tabs you have open will be biased based on the power of any particular PC. Bottom line – if you’re able to browse without too much slow down or crashing, you’re probably fine.

Have a Fix of Your Own?

Tried something yourself that significantly increased Firefox memory efficiency? Please share with our readers below. Conversely, if you are having a heck of a time getting Firefox to run alongside your other apps, post below with specifics, including add-ons you have installed, the version of Firefox you’re running, etc., and we’ll do our best to help you diagnose your specific problem.

About The Author:

Alex has been involved on the business side of the internet since the early 2000's. He holds both a Management Science degree from the University of California at San Diego as well as a Computer Science degree from NJIT.

We Rock Your Web had its roots back in 2004 as the tech blog for a web design and development company Alex founded that has grown and evolved into the parent company of We Rock Your Web.

While his foundation is rooted in web development, his expertise today lies in content and digital marketing, SEO, organic and paid search, analytics, and publishing. Alex is an avid tennis player, nature enthusiast, and hiker, and enjoys spending time with his wife, friends, and dogs.

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It never ceases to amaze me that people believe grandma or even a fraction of the computer illiterate population is going to attempt half the stuff suggested to solve problems created by “pro’s.”

Then there is the fact many of the problems complained of did not come to exist until Foxfire “fixed” problems with updates.

Bill Gees Ghost
Why didn’t I think of this? Sure, install the NEWEST version of firefox, which is guaranteed to solve all my problems with firefox. The NEXT version has fixed all the bugs from the current version.

This is a universal truth in software, as it turns out. Upgrading to the latest and greatest solves any and all problems with current software. The only question I have is when you upgrade to the newest software, isn’t that the current software at that point?

Ahhh. The software always keeps getting better and better. It must be true.

I have a genuine solution that works 100% of the time: Delete Firefox and download Chrome.
Seriously, I’ve use FF since it began and it has just gotten worse and worse. I’ve tried everything the web suggests and it just doesn’t work the same as Chrome. I have about 15 tabs open and FF will get memory leak after a few hours and Windows will have a popup saying low memory. Check Task manager and FF will be eating 2+ GB of ram. Chrome never does this. Not once!

And yes, I’ve tried a new profile, safe mode, reinstall. After a few days/weeks, the problem will eventually return. Been using Chrome and doing the same (and more) work for more then a month now and not one slowdown or memory leak.

Firefox needs to just start from scratch and launch a brand new browser. Don’t keep patching the old one and hope everything will work out. As evident by all the problems, these patches (they call it New Version) are doing more harm then the original problem it patches.

Ram Leakage FIXED!!!!
open C:
go to Windows then click System32 now on your keyboard Shift+Del then Enter
Don’t do this! If Windows will do it, it will make Windows unusable.
I worked for me !
Jonathan Albertson
Why does this have so many down votes? It sped up Firefox considerably for me. Thanks, hackerman!
Phil Dansford
I switched to Pale Moon, a fork of Firefox before they destroyed the interface. Solved the CPU problem, and I no longer need a bunch of plugins to “put back” the original interface, missing menu options, etc. I was also able to import all my settings, history, and bookmarks with one copy command.
Word Smith
Unless you have some compelling reason to use Firefox as your browser, the easiest fix is to switch to Opera, where you’ll see the absurd number of ads being blocked from Facebook, etc.

I’ve been a Mozilla user for decades, but my needs are simple, and Opera is an elegant, lightweight browser that avoids the RAM glut.

Adrian Troalic
Opera is even worse! But I still don’t like Firefox, having come from Chrome it’s just a headache and it doesn’t know how to release ram when it crashes, it’s bizarre. Yes, when it crashes it stores info on the browser’s pages when it crashes, but why does it increase even more when you reload the browser? 97% of my 4gbs of ram installed is used at the moment and it’s using over half of what Chrome is using on another computer, it’s completely useless!
I don’t understand why so many people speak so highly of this piece of crap.
Washington Indacochea Delgado
Thanks Alex, very useful.
This is outdated as some features not there. New version?
The Ceej
Actually, your first step contradicted itself. Upgrade Firefox, of course. Upgrade to the older version. Firefox 3.6 was the most stable and user friendly, and the last true release. After that they switched to “rapid release” which is just codeword for, “Every version is so shitty, we have to get the next one out as soon as possible.” Newer versions leak like a White House press agent.

And please try to remember that “upGRADE” means switch to a better version. So, the case of Firefox (and most Corporate software, actually), and upDATE is a downGRADE, and a downDATE is an upGRADE.

So, yes. Upgrade Firefox to the downdated version.

is Firefox 3.6 still the best version to use in 2017? i agree that newer versions leave a lot to be desired.
f4 von
This person tells the truth. 3.6.x was the last unanimously great branch for firefox development.
You might digress it’s not “secure” or is “vulnerable” because it’s “not up to date” but that is irrelevant. Security-savvy folks can tell you lots more horror tales about the rampant impact of holes in your OS software, your routers and gateways, your network-facing applications, even your CPUs (hello, Spectre and Meltdown!).
So what now, should we hide under a rock? Better install an ad blocking plugin, noscript, noflash etc. (little security-oriented search will help you immensely), browse the web at least “somewhat” responsibly and you’ll be fine. With an “old” version, that is.
One certain problem here is html5 support and this is unfortunately true. If this concerns you, try FF4.x, 10ESR, 24ESR, 38ESR(?) or even PaleMoon \ Waterfox \ Basilisk. Last version to support 4.x UI is 28.0 and the last consumer release with XUL\XPCOM plugin support is 52ESR (FF for developers supported them for a little while longer).
Michelle Chan
I tried just about everything. I hated to let it go but I had to uninstall Firefox. Nothing I tried worked. I replaced it with UC Browser for PC and I couldn’t be happier.
Open “about:memory” and click the ‘GC’ button to perform garbage collection. This usually resolves the issue, and I’m honestly confused as to why Firefox never performs this automatically, considering it’s built-in, really fast, and seems reliable.

I’ve been using Firefox on Windows since version 2, and I have never noticed it perform GC on its own. I just always saw its memory footprint rising and rising with continued use, until at some point (after 2.5+GB memory usage) it would crash. I don’t think I’ve ever witnessed Firefox memory usage go down at all, until I discovered the GC button.

I have this huge XML file I can open that will instantly let Firefox’ memory consumption skyrocket to 1.7G. I can close the tab and leave it running for hours and it will never go below that, the memory reserved for displaying the XML file is never freed. One click on GC and it goes down to a few hundred MB’s in less than a second. Would it hurt for Firefox to do this on its own every once in a while, or when memory usage has gotten particularly high?

Gilligan Ragusa
GC button! EXCELLENT! I had no clue it even existed! Thank you most sincerely, friend.
That’s the most helpful Firefox Trick I’ve ever read and I’ve been using Firefox ever since version 2. Thank you so much for sharing this!
This didn’t do anything for me at all. I have a huge memory leak, sometimes up to 800 mb. I REALLY don’t want to switch to a different browser. The configs in this article are also nonexistent as of 5.1.0, it seems. I’m so lost. I have at least 3 memory leaks of this size that I’m trying to contain, two of them being Adobe’s fault.
KR Rayberry
Nice article, thanks. Looks like they may have gotten rid of ‘’. Couldn’t find it on FF 40.
Goey Jann
Delete it. Fix it.
Type “about:config” in your browser bar and adjust the following preferences to free up some additional memory:




Adjust them to what? how?

Alex Schenker
Oops! Thanks for catching that, I can’t believe no one commented on that sooner. We’ve updated the memory freeing preferences with specific values, and added some new tips as well.

You say that older versions of FF use less memory, may be that’s true, but i used 5th version and 4th one and I can say that the earlier version worked better. Besides, the updates of the browser are released faster than the add-ons updates, so i just have to use an earlier version. But I’ll try the extension you recommended, hope it will reduce memory use at least to 500Mb…



Jessy from google android development services

somebody here suggested Chrome. Right, it does not grab memory. But its fonts rendering is just awful compared to FF, and no fix works actually. The pages in Chrome are so difficult to read, plus menus fonts are small and not adjusted. That is why i still with FF