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Firefox has extreme memory leak

  • 99 replies
  • 2411 have this problem
  • Last reply by Marco Lopes

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After using Firefox for several hours, it begins consuming more than 500mb of memory.

This happened

Every time Firefox opened

== I began using Firefox 3.3.6

After using Firefox for several hours, it begins consuming more than 500mb of memory. == This happened == Every time Firefox opened == I began using Firefox 3.3.6

All Replies (20)

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Try the suggestions in Firefox uses too much memory or CPU resources - How to fix. Most of the time, high mem usage is due to plugins like Flash, so if you hold on for a week, Firefox 3.6.4 will include a feature that separates plugins from firefox.exe. :-)

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thanks, release of Firefox 3.6.4 is great news. :)

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Same here. I can take even 1,5 G memory, before freeze....:( It seems NOT to be plug-in related ?

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Firefox has always been terrible for memory leaks along with errors such as "Script: chrome://global/content/bindings/browser.xml:0".

I love firefox for its customization but the memory leaks and Javascript problems are just unbearable for me.

I have to reboot the browser once per hour to fix memory leak and I have to enable and disable javascript to stop chrome errors for individual sites.

This is regardless of plugins installed and Re-installing firefox once per week makes it no better either.

I'm on latest version 3.6.3 using Windows 7 x64, Intel I7 4ghz CPU, 6Gb or Ram, more than 50% free space on all my 6 HDDs.

I have 3D rendering applications that run faster with less problems than FireFox.

I wish they would sort it out.

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FWIW, Firefox 3.6.4 is delayed until early June. https://wiki.mozilla.org/Releases/Firefox_3.6.4

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I think you'll find that FF, plain wrap, doesn't leak - in general, it is the add-ons.

I had time today to diddle with mine as my CPU usage was unacceptable, but didn't want to go back to Safari as I love all my favorite helper add-ons in FF that make my browsing my enjoyable.

In my case, the only culprits that I found were FoxyTunes and CoolPreviews. For any other user that may read this, I was able to fix the leak in CoolPreviews by downloading today's update which also has a fix for the PacMan alarm siren that went off if you went to Google today and had CP enabled.

I found the following webpage very helpful to start:

Problematic extensions - MozillaZine Knowledge Base http://kb.mozillazine.org/Problematic_extensions

If you want to test all of your add-ons, you can start in SafeMode (hold down the OPT key when starting FF) and disable them all. In my case I just started down the list, enabling several at a time to make the chore faster.

I know the AVG add-on is also a conflict, I will have to turn them off when I get back to the Win machines at work.

You might also check your plugins.

Good luck!

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The memory leak is ridiculous, to the point of making the browser essentially unusable.

The Add-on-causation hypothesis nonsense is absolutely untrue - I have been testing Firefox for more than a year, and it is without a doubt the most unstable browser out there (and that, gasp, includes IE8).

The MAIN PROBLEM seems to be that people who do not experience the memory leak/freeze/crash issues with FF don't tend to operate many tabs at once, maybe a dozen or so. Additionally, they seem to turn off their browser/computer more often, enabling cache clearing on all levels.

Those like myself however, who operate up to 50+ tabs at a time, never restart my machine, AND only restart FF when it crashes (which is often) are suffering tremendously from this problem with the browser, which release after release, has gone unrepaired.

Once again, the add-ons are not the true cause of this problem, some add-ons/plugins do indeed make the problem worse (like shockwave), but even with everything off, the instability is rampant.

There is an inherent coding problem with Firefox software (and perhaps its relation to Windows?) which is causing this. Continually claiming there are workarounds is not an acceptable solution.

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Hello everyone.

This problems are not, in 99,9% of the cases, Firefox's fault. Rather, they are caused by problematic add-ons or third party software. But you do need to diagnose what your exact problem is. Do this:

  1. run Firefox in safe-mode to disable all extensions, themes and plugins. If this fixes your issues, be them with RAM or CPU usage, then you know it's a problem with plugins, themes or extensions. Proceed to number 2. If safe-mode doesn't fix the issues, then read bellow, after this list;
  2. update all extensions, themes and plugins in your Firefox. If this doesn't solve the issues, proceed to the following number;
  3. disable all extensions, themes and plugins in your Firefox (not running safe-mode). Being certain that, as in safe-mode, the problems you're having have gone away, enable one plugin at a time. You should be certain that you WANT that plugin to be enabled, so keep your overall number of plugins as low as possible. When you encounter the problems, you know you've found a problematic plugin, so disable it for good. Keep enabling all plugins (except problematic ones) until you've gone through them all.
  4. enable one extension at a time. Again, be certain that you WANT that extension to be enabled, so keep your overall number of extensions as low as possible. Also, try the theme you want to have installed so see if that is what's causing the problem. When you encounter the problems, you know you've found a problematic extension/theme, so disable it for good. Keep enabling all your extensions (except problematic ones) until you've gone through them all;
  5. you're done! You've fixed your problems with problematic add-ons. If you want to keep using those problematic add-ons, please contant their author for support.

Ok, if disabling all extensions and plugins through safe-mode didn't work to bring Firefox's CPU and RAM usage to good levels, then you have different issue. The most likely scenario is that you have a third party software running on your computer that is messing with Firefox. Do as follows:

  1. try reinstally Firefox. No data will be lost. You can get the latest version for free at getfirefox.com. If that doesn't fix the problem, proceed;
  2. do a virus/malware check on your computer. If this doesn't fix it, proceed;
  3. disable all software running in the background that you don't want to have running in the background (in windows, this is done by pressing WINDOWS+R in your keyboard, typing "msconfig" (without the commas) and pressing enter. Now, under the "Startup" tab, you can uncheck the software you don't want, and reboot your system for changes to take effect. If you're unsure of what software you want running, ask someone with more experience). If this doesn't fix your issues with Firefox, proceed;
  4. check your firewall/antivirus/security suite for enabled functions/features that you don't want and/or may be conflicting with Firefox. You'll find that these features are most likely tied to Internet Security features, such as link scanners or URL checkers and the like. If you're not sure they are conflicting with Firefox, simply try to disable them to see whether or not that's true. As long as you don't browse the web with your antivirus completely off and your firewall completely turned off, there should be no problems. If this doesn't solve the issues, proceed to the following number;
  5. check your operating system security options, mainly advanced options that are not configured by default. While it's very unlikely that this may be the cause of the problem (after all, it's the last item on the list), it's remotely possible. If this doesn't work, proceed to the following point;
  6. clean up your OS registry, using appropriate software. If this doesn't do it, I'm out of ideas. Except make sure you've followed my instructions correctly.
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New computer (Win7), *no* addons, FF bloats to 500M+ RAM with minimal use.


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Hello Anonymous.

Be sure to follow the instructions in my post to the end. Some security software, malware and other third party programs my mess with Firefox too.

And be absolutely sure that Fx (the correct abbreviation for Firefox) has no add-on installed: check under Tools > Add-ons > Extensions and Tools > Add-ons > Plugins. Sometimes, people install add-ons accidentally, when installing other software in their computer.

I hope this helps.

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Will do and will report results. This is a clean computer, so I will be interested to see what step actually fixes it.

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Kudos to Morbus for being extensive in his proposed solution - I really appreciate that level of thought about the problem since I've been obsessed about it for so long.

Despite having completed a LOT of "Fx" fixes, deepdiving, etc., I have followed this procedure with excruciating attention to detail, on three different machines.

One is a garbage laptop which I won't even name the specs on.

The other is Empire of Dreams (yes my machine has a name). The brief specs: 4.2 GHz OC Core i7, 12GB RAM @ 2133Mhz, 2 Vertex 160GB in RAID0.

The other is my other machine which is middling in specs, with 3.8GHz AMD, 4GB RAM and a 10K Raptor, this one JUST got a fresh Win7 install.

Worth noting - none of these machines run antivirus, etc, but all were scanned with several of these programs, then they were deleted.

Now as I mentioned in my post... the number of tabs Fx runs is crucial to replicating this problem. running 10 tabs tends to put all 3 of the tested machines at 200-230MB RAM, which seems like a lot, but doesn't bother me (at least).

However, I am a hardcore 'Net tourist. (usually run 8 different browsers with 350+ tabs). Furthermore, I often leave tabs open for days without restarting the machine.

Running Fx with 25 tabs on each of these machines provides results:

Laptop: 500MB RAM (almost an insta-crash obviously since this machine has 1GB)

EmpireOfDreams: 800MB (the memory usage here isn't a problem as there are 12GB) BUT Fx is completely unstable, locking up, crashing and requiring restart, etc. This occurs after about 1 DAY of being open. Restarting the browser does not help... HOWEVER restarting the browser without any of the original tabs (clearing the browser and restarting it) returns the browser to a functional state (though memory usage is still 800MB or so, spiking on occasion)

Other Desktop: Almost the exact same phenomenon is observed here, leading me to conclude something is wrong with Fx... and that there is no mystery as to why other browsers don't exhibit this problem as radically (though they do, notably, express it to some degree: Chrome, Opera, IE, Safari, Flock, and Maxthon all do for example, though none as badly).

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Firefox also crashes if you have simply too many YouTube tabs open at once.

I don't get this with the other browsers (yet at the same time can't stick to them & return to firefox).

For browser stressing when surfing firefox is easy to crash without even trying.

Annoys the hell out of me as I am usually doing 6 different things at once (mixture of work, research & play).

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@the Commisar, lol, your Empire of Dreams is pretty extreme, good job building that monster. Anyways, the thing about Firefox that I find maddening is not the extensions but the Plugins.

Morbus already touched on this, but it is worth repeating. Go to Addons~~~>Plugins and disable everything you don't need. Including Java console etc etc. I disable everything except flash b/c I am just a general user and don't need any of the other stuff. Disabling unneeded plugins is a good thing overall b/c its provide malware people with less vectors to attack Firefox.

However even with this, I notice Firefox still leaks, but not as much. Watching videos with Flash causes pretty big jumps in memory usage and Firefox does not let go of the memory well even after you closed the video tab. At most I have 20 tabs open and my iGoogle page auto refreshing, but my firefox goes up to the 250-300 megs after several hours.

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I use about 25 extensions and never have less that 50 tabs open. As you can image, my RAM usage is pretty high (but it doesn't increase over time). Right now, with 30 open tabs, I'm using 300MB of RAM. If you open Google Chrome, by default, and open 30 tabs, it will easily surpass that level.

Still, what you describe is not normal behavior. However, I'm not sure whether this happens with or without add-ons. You say you've followed my instructions to the line, in which case you've either managed to fix your problem or you've created a temporary new profile to try to replicate the issue with it, yet you don't say whether you did fix the issue or if the new profile still has it.


You may be having a problem with some extension or plugin that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?


Flash is also known to cause issues with some people. If you don't disable Flash and still experience crashes and other problems, try disabling Flash and see if that helps. This is just for diagnostic purposes. If you need support with Flash (or any other add-on), contact its author.

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I certainly did NOT "fix" the problem...

It's worth noting that the memory leak itself isn't really a problem for me (esp. now with a 24GB RAM upgrade as of yesterday) while at the same time it's hardly a good design.

My problem revolves around Firefox crashing, freezing, and generally being unstable after its been left on for a long time. Even then I'd be ok with a restart but for the fact that it remains unstable until I kill off every tab, THEN restart (restarting with the legacy tabs from a previous session doesn't fix the instability).

I followed all the suggestions - the only thing that killing the addons and plugins did was lower the basis memory usage, and slow the memory leak, but it didn't eradicate this instability problem overall, and after about 24 hours, the browser was again crashing a few times per hour until I bookmarked all the tabs and restarted clean (which is MY current 'workaround' for Firefox).

Now... I did do this on 3 machines with similar results. Addons/plugins don't seem to 'cause' this problem, though their removal alleviates it. I don't understand why this problem exists to begin with though. And yes I acknowledge Chrome et al. also use a lot of memory, and I don't WANT to use Chrome, I want to use Firefox, which I do prefer.

But as a corollary... Part of the major userbase of Fx favors it BECAUSE of its extensibility, and frankly, the inability to load Flash pages because of the KNOWN Shockwave memory problems with Fx is unacceptable in a world where Flash is ubiquitous (Steve Jobs' campaign aside).

I seriously hope that the next version of Fx increases the stability significantly, even it that requires some kind of restart or cache-clearing every so-often. There's just no reason why this should be happening, add-ons or no.

I'll also note that Opera10 is by my experience, and by some consensus, the fastest browser available right now (unless you're on a netbook or somesuch in which case Chrome probably would be due to process discretion). It's more stable, but also uses a lot of memory.

For now... I'm working with the "bookmark all tabs, hard close, restart Fx" workaround.

I'm also btw not spending hours of my time doing all this to bother you people on the Mozilla Support site (not that anyone said I was), I also work with a group of people who have almost identical problems as myself with similar browser use profiles.

What I WILL NOTE OF PARTICULAR INTEREST is that Flock is built on the Mozilla platform but doesn't express the same issues as Fx - it's actually quite stable, and I use it for all my video-usage (Youtube, etc.) because it runs the Shockwave Director much better than Fx in my exp.

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TheCommissar, you are experiencing problems with Firefox, problems which are not common to all users.

You did try creating a new clean profile (managing profiles), right?

If the new profiles still have the same behavior, I would be on some kind of software incompatibility or something like that... Because Firefox is very stable on my end, loaded with extensions and using many extensions and keeping it open for weeks at a time. These problems are triggered by something. Finding that something is definitely all that matters.

What do your crash reports say? (Getting your crash report)

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@ Morbus "Geek here, one that is in charge of the browsers on 100+ computers.

I moved from Firefox to Chrome (personally, and on the machines I support) not because of any single feature, and certainly not due to any loyalty or ideology.

Chrome simply ran faster and caused less problems for me and my employees. I have the support ticket data to back this up.

In particular, the Firefox tab memory leak that people keep telling me was addressed several versions ago was STILL hitting about 1 in 5 of my installs. After a few hours and several open and closed tabs Firefox would be eating up every ounce of system memory. No such problem with Chrome.

Beats me. All I know is I haven't fielded a browser related support request since the change.

Short of Chrome having similar troubles, I can't imagine switching back.........."


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Ok... some results finally.

Running Fx on Windows 7 is just not happening for me - nothing I've done has 1) stopped the instability problems and 2) decreased the memory usage.

So I ran a virtual machine of Kubuntu/Fx. I was initially just fooling around, as I assumed the extra layer with the memory would be even worse.

It turns out that (with stock Fx, absolutely nothing added-on) the browser does a modest 540MB of RAM on 43 tabs, but more importantly, is stable going on 60 hours of continuous use and disuse.

So I suppose I've fixed the problem of how to use Fx... though it involves using a different operating system... and NOT using any of the extensibility Fx is famous for... (and in my case a virtual machine).

I still maintain that there is a Windows-related issue at work here (history is kind of on my side anyway with that). Fx had been better on my clean 7 install - but not astronomically so.

My conclusions after months of this annoyance are the following:

1. Fx works on Windows, though I can't do the 70+ tab heavy lifting I want to (fairly, other browsers are taxed by this as well, they just don't crash so insanely often). While I know most users aren't going to care about this... WHERE IS MY INDUSTRIAL QUALITY BROWSER THAT CAN RUN 1000 TABS WITHOUT BLINKING AND BE EXTENSIBLE?

I would pay for such a thing if it existed. $1000 easily for a license, probably more.

2. Fx is slipping technologically vs its browser competitors, namely Opera and Chrome. I REALLY don't like Chrome, and its process-oriented memory usage is very annoying, not to mention it doesn't have addons, etc. I love Opera, but its adoption isn't wide enough for compatibility and addons (widgets to Opera)

3. The notion that to 'fix' Fx (which I couldn't really do anyway) requires 1) not using Flash, and 2)not using addons... is fundamentally flawed. The entire point of the product is to be able to use it in all its conceived glory, and I really have some heavy Fx loyalty in terms of the project, open source, etc.

But you can't keep telling people to turn features off to make their browser work, especially when most people are using the same (windows) platform - I can't speak for Mac users.

4. I'm going to be using my usual suite of Opera, Flock, Chrome, Maxthon, IE and yes, Fx, for now... but I won't be wearing my Firefox T-shirt again until they fix these memory/stability issues - hopefully in the upcoming release.


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I'll post the crash logs

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