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Firefox 4 is unusable due to excessive Memory usage - when is the fix?

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  • Igcine ukuphendulwa ngu the-edmeister

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There are just so many people complaining about Firefox 4 - all with the same basic problem - Firefox 4 consumes far-too much memory and appears to increase memory usage over time.

So far I have heard NOTHING from Mozilla regarding this problem.

Have Mozilla identified the problem? Is there a work around? When will there be a permanent fix?

There are just so many people complaining about Firefox 4 - all with the same basic problem - Firefox 4 consumes far-too much memory and appears to increase memory usage over time. So far I have heard NOTHING from Mozilla regarding this problem. Have Mozilla identified the problem? Is there a work around? When will there be a permanent fix?

Okulungisiwe ngu IanSeale

All Replies (20)

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The problem is likely, in my opinion, to relate to specific websites and or specific extensions. You will need to narrow down what causes a particular problem, for instance: try in firefox safe mode, with only any essential extension in use. Try to work our what sites the problem is seen on. ( A long shot but also try to see if the problem is only whilst the firefox 4 html5 parser is enabled. )

So to answer your question, I personally have not seen any indication of a general problems

  • or do you know otherwise, - can you link to specific examples please ?
    ( preferably recent with an active user able to provide further info )
  • if so has anyone filed a bug on the problem ?
    which will first of all require someone to find reproducible problems
  • see also Firefox uses too much memory or CPU resources - How to fix

Remember with millions of Firefox users, some are always going to have problems and even if only 1 in a thousand users have problems there are still thousands of people having a problem, but millions who do not.

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Well, I think if you perform a simply Google search with the relevant key words you'll find plenty of people with the problem: all disabling Add-ons all disabling Hardware Acceleration all experiencing problems with many different websites all having a problem with Firefox 4's excessive, and continually climbing, memory/CPU usage and, most importantly, all NOT having a particular problem with Firefox 3.6.16

I don't need to chop a change my configuration/usage in Firefox 4 - it is Firefox 4 which is badly set up, not me.

I, and many others, want more constructive answers from Mozilla.

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I am sorry if my answer is not helping with your particular problem. ( I personally do not notice problems, of high memory use when I use Firefox4, and I am certain many others have no problem. )

This is a support site, it will help you with individual problems, but even attempting to do that will often require anyone with a problem to take certain troubleshooting steps to determine what exactly the problem is.

If you see a problem with Firefox overall a bug needs to be filed and the developers will look at it. Obviously Firefox 4 will have been rigorously tested, over a million users taking part in its Beta trials. Thousands may have problems, that does not mean Firefox 4 itself is at fault, only that Millions of users use Firefox, and some of those will inevitably have a problem.

There are probably thousands that use Firefox and whose favourite colour is pink, if you post that Firefox does not work and your favourite colour is pink you would inevitably getting someone agreeing with you. (And if any such correlation proves anything, possibly it would lead to the discovery that some theme customising Firefox to look pink is problematic. Normally it is just the Maths, with millions of users all sorts of correlations can be found, but do not necessarily demonstrate causality)

Another example I often give is that breathing must be bad for you.

The more breathes you have taken, the higher your likelihood that you will have died or will do so in the near future. Until suspended animation becomes a routine reality, stopping breathing entirely is normally not a good idea for prolonging healthy human life.

Firefox is highly customisable, it is likely it is some of those customisations that contribute to problems. Firefox is also available on different platforms, that adds another layer of complexity when looking to identify problems.

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Oh for crying out loud...what, are you taking lessons from Microsoft Tech Support? "There's nothing wrong with our product, the problem must be with THEM, their stuff isn't compatible with us. Or you're just using it wrong."

SHUT UP, JOHN. You're doing spin control and you know it. Firefox users have been complaining about this for YEARS, and the number of complaints keeps going up with each update. The problem is getting worse, not better, and it's obviously because Mozilla just doesn't care...because it couldn't possibly be this hard to really fix it if they actually applied themselves.

It was a HUGE mistake for me to allow Firefox to install version 4 on my machine, the hanging and crashing was nearly instanteous. The install was at 9:30 this morning, it's now barely before noon, and I've already had to force a shutdown three times already. This product is completely unusable.

I've had it. I can't stand this any more. The only reason I didn't quit using Firefox a year ago is that Chrome doesn't quite work right with the proprietary website I have to use at work. I can't stand the way the interface looks on Explorer, BUT AT LEAST THE FERSHLUGGENER THING WORKS. Mozilla has done the impossible: they've pushed an ex-Microsoft user back to Microsoft. Congratulations!

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I am not doing spin control, just explaining, as another ordinary user my opinion

  • this is not paid for software,
    and lot of troubleshooting & support is done by ordinary users.
  • you need to help if you want an answer about such a problem,
    because the less frequent a problem the less likely its cause will be already known.
  • with something like 100 Million users of firefox some users will have problems,
    • including with high memory use.
    • high memory use is often related to how firefox is used and with what other software
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Man, are you blinkered! Are you receiving these messages on your planet? Have a look here:

There is a MASSIVE problem with FF 4 which has absolutely nothing to do with everything you listed.

If those are your answers, I'd rather you didn't 'help'.

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It appears you do not wish to have any help,
and do not wish to try to show what does and does not work or cause memory problems. If you just wish to provide feedback one of the other sites may be more appropriate eg

If firefox 4 is the problem why not just revert to firefox 3.6. ?

  • that solves your immediate problem
  • If you can show the problem exists in firefox 4 but not firefox 3.6 you are starting to make a case for filing a bug and getting the problem fixed.
  • But imho just searching for the phrase firefox 4 sucks is not constructive.
  • You mention disabling hardware acceleration - again that is an option
    • if hardware acceleration does not help or causes a problem do not use it
      but then lets try to discover what hardware or software it causes a problem on
    • does an updated video driver, or revised extension help ?

There will be unresolved or undiscovered issues, but they will not be resolved or discovered without suitable information.

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The first 2-3 weeks after I began using Firefox 4 it worked fine, but for the past several weeks (late April onward) whenever I come back to my PC after an hour or so it either displays a blank window and is using close to 2 MB or memory, or has crashed. This happens multiple times per day.

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Hi pgross66,

Sorry you are having problems. More info would help and it is probably best to start a new thread with specific details about your problem and your setup.

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The people on here complaining need to take a deep breath. I'm looking around on the forums for some info and I noticed this thread. Mozilla did not sabotage the app. I'm not having any major problems at all with FF and I have it installed on two computers. There is a small issue on one of them, but I'm working on it and the issue is not causing me to think that Mozilla has somehow destroyed FF. The guy next to me has FF installed on both of his computers. He's not having any problems or complaining about it. Most likely, it is a problem that you've somehow caused.

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Most of the people with the High Memory Usage problem on Firefox 4 - didn't have it on Firefox 3 - didn't change any behaviour, didn't change any programs, didn't change any hardware and aren't running any out of the ordinary applications - the only change was Firefox 4!

The only real commonality that I have found is that it seems to effect, or be more noticeable or have 'more' effect on older operating systems.

But from a diagnostic standpoint, the only thing that has changed is Firefox 4, all other things are equal, and therefore it IS Firefox 4 that has, or is creating, the problem.

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John99, I’ve experienced the same. I installed FF4 2 days ago and immediately experienced problems with excessive memory use and FF regularly freezing. On installation and restart it had exactly the same websites open & exactly the same add-ons & extensions as my previous version of FF but memory use almost doubled. I’ll notice the hard drive light flickering madly; when that happens the memory used is increasing (without any activity on my part – I’ll just be reading a page) – it will climb from low 300 thou K to over 500 thou K (as reported in Windows Task Manager). FF remains unresponsive & hence unusable. I made no other changes to my system.

Nothing is being downloaded, again according to Win Task Manager. Other programs being run concurrently are minimal – Windows Mail & MS Word. Again, absolutely no different to previous versions of FF.

Recent event: Went to open one page - FF not responding went for well over half an hour, then abruptly all settled down and I was able to open several pages without incident.

‘You will need to narrow down what causes a particular problem’ I have already attempted the standard procedures - disabled add-ons, run in safe mode – to no effect. The excessive memory use remains & this is with half the number of tabs open. As mentioned previously I had exactly the same web pages open as in the previous version when this problem did not occur. There are no particular sites causing problems – I’ve experimented opening & closing various pages. It often seems to happen after a period of non activity, ie where I have been reading a long page or been away from the computer. The first (& I really do mean the first) time I click on FF4 the @##$% thing freezes.

‘( A long shot but also try to see if the problem is only whilst the firefox 4 html5 parser is enabled. ) ‘ What? I don’t have a clue what this means – I’m a user not a developer or programmer.

further info: exactly what ‘further info’ is required and exactly how does one obtain it…remembering again that I am a user not a programmer!

I've spent hours on this - the latest was based on advice I read elsewhere on these forums. I installed Leak Monitor version 0.4.6 On reopening Firefox (with 14 tabs) there were eventually over 100 leaks reported – the number grew as I tried to close them. One report generated over 100 pages!!!! I would close report windows and more would open. There were 2 types of leaks: Reclaimed leak alert, and New leak alert. Unfortunately none of this means anything to me & may not be relevant... and if it is how on earth do I gather information from over 100 alerts?

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Hi IslanderCirce,

If you start your own thread it should guide you, and partly automatically, take additional information. You obviously have already taken the usual steps to track down and reduce the problem.

Maybe see what happens if you just open firefox in safe mode with only a blank page? The more tabs you have open the more memory will be required.

The html5 parser may be disabled by one of the prefeerences, but that is as I say only a longshot, and only likely to affect certain sites. Are you using sites with heavy graphics animations or videos ? What sort of numbers of tabs do you typically have open, single figures, tens or hundreds ?

What is your sytem OS and how much RAM do you have installed ? I am curently using a Windows XP legacy machine with less than 1GB installed RAM available. On that I may simultaneously open and run Fireox 4 and Firefox 5 , video may become more like a stop frame cartoonor not play, but it will continue to respond and opens multiple tabs of ordinary pages without problems.

Another long shot but when you are checking memory use in Task Manger, also worth looking for plugincontainer.exe, because firefox may open that to deal with some plugins, and I think there is a bug still where it may open many instances of this when action is taken to clear cookies. In this case it will even open disabled plugins !

If I was in your positon I think I would install firefox 3.6 again, so that I had a working browser, then install firefox 4 as a custom install as a second alternative. If you do consider going down that route you will need to use separate profiles for each browser, and pleae be carefull if you do any uninstall NOT to use the delete data option, or whatever the wording is, it will delete all bookmarks and passwords etc from ALL installed versions.

At the moment Profile Manger will probably be used if creating an aditional profile, that however is being phased out, the aurora channel already having a ttrial of a channel switching feature.

If you do need to use the memory leak tools that is something I have no experience of, someone else may be able to advise on that, but I suspect you would be more likely to get help about using that on another forum. It is my understanding that final releases of firefox in safe mode should not have serious memory leaks in ordinary situations. If such memory leaks do occur it would seem to me to be a bad and unexpected flaw in firefox 4.

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Ian, Just to support you. I have been using Firefox for several years, and I have recommended Firefox to others. I'm not sure anymore.... :-( The PC at work has Windows XP and the latest FF 4.0.1. No add-ons used. 2gb of RAM installed. I never shut down my PC when I go home, and my browser is up and running with approx 10 open tabs. In the morning, FF has occupied aprox 1gb RAM! And if the browser is in backgruond and I start the Task Manager, the TM shows that the memory usage is continuously increasing! Even worse: If I close FF with the red cross, the memory is still occupied, and still increasing. Cancel process in TM is the only way to stop it. John, do you have any explanation? Seems that Google Crome is the only answer if FF can't solve this.

Hope somebody at FF development can take this serious. Because this kind of experience makes me to think twice before I use free software. Customers expect to be taken serously when they report an error, free software or not.

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Hi Obach,

It sounds like you do have a problem that needs fixing, or as you say firefox has a problem. This site is for support and asking qustions, but there are other sites for

If you have a genuine and reproducible problem please file a bug, or at least provide enough information and help for someone else to file one. Problems need identifying and reporting if they are to be in with a chance of being fixed.

I have not yet seen this problem. Start a new thread with full details and if I can reproduce the problem I will happily file a bug if you do not wish to. I do have aWindows XP I could leave on overnight. Can you give me a list, or better a couple of lists with different sites that I could try for that experiment.
(I suspect if for instance I leave 10 tabs from this forum open overnight I will not see the problem - which of course may lead to the problerm being identified as a fault with the sites you are using not firefox)

Okulungisiwe ngu John99

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Hi John99 Thanks for your information and suggestions. It gave me some other things to consider. I was close to reverting to Firefox 3.6 and possibly have version 4 installed on another drive but my innate stubbornness got in the way. I decided to keep investigating and also keep a diary of absolutely everything I did and how Firefox responded.

I found much discussion about memory problems, especially on the adblock forum - adblock forum with many references to bugzilla and known/reported memory leaks in FF4. Some interesting information & discussion here: and a list of reported memory leak bugs here

All the reading and comments had me thinking a bit differently. After a while I realised that, while the memory might be running high, this was only a symptom. The real problem was Firefox hanging. Chasing that up I came across this - - and followed the advice there concerning multiple copies of Session Restore files. After deleting all but the most recent of the session files there has been no repeat of the extreme problems I was having. I’ve had nearly 50 tabs open at a time (fairly standard for me) and memory used was similar to that of Firefox 3.6 – about 290Mb. Prior to deleting the multiple sessions files the memory used for 4 tabs open was about the same.

Being cautious, I’m only gradually adding back various extensions and plugins but I’m now feeling confident that the problem has been solved. In the last day there have only been 2 minor hangs of less than a minute duration each. I can live with that.

Hoping this information may help others.

I do think that Mozilla’s organisation of its help could probably be improved – some better cross-referencing and perhaps a list of diagnostic questions to help guide users to the right help.

Okulungisiwe ngu IslanderCirce

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Thanks for posting back, and including some links. Glad you seem to have solved your own problem. I will have a look at some of those links myself later.

With things like memory use or speed of operation there are many factors that will be involved. Feedback showing how many users are having problems is obviously going to be useful but for individual problems detais enableing a reproducible testcase are needed.

You probably have already seen

The Mozilla Firefox help articles are discussed in these Firefox Help forums

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Well, I'll throw in my two cents worth.

@ IanSeale, I checked your system details and note that you have some very old plugins installed which potentially exposes your system to attack.

In particular Adobe Acrobat because the version you're running dates from May 2001. See

Adobe regularly releases advisories and it's wise to keep abreast of these for your own system safety. The latest advisory can be seen here:

So it really wouldn't surprise me to learn that the reason for the high memory usage on your system has nothing to do with Firefox, but rather with the malware you probably have installed.

Therefore, in the first instance, I'd recommend you download the free version of Malwarebytes from and run a full system scan.

After you do that, do the following:

The main reason you should also update Firefox is because there was a security breach recently at Comodo which is an SSL certificate provider whereby a number of fraudulent certificates were inadvertently issued. These allow a hacker to impersonate any site including online banking and the Firefox version you're running at the moment will not warn you that the site is a fake. The fraudulent certificates were blacklisted in v3.6.17 and beyond. See

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Sorry Xircal, no Malware - I run SUPERAnti-Spyware pretty regularly and I'm clean as a whistle. And, like I said, I WAS running fine on 3.6.16 and I AM running fine on 3.6.17. Thanks for the links. I'll update Acrobat Reader, but if that fixes the problem I'll eat my hat.

Okulungisiwe ngu IanSeale

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I just stumbled across a thread and a blog: solved-firefox-freezes-every-10-seconds that you may find of interest. Someone commenting on how firefox can use a lot of memory running sessionstore, an investigation done with no more than a replacement task manager. The blog concludes with two workarounds.

Probably the most useful reference about memory problems is, rather than a simple search, this bugs meta list Bug 640452 - (mlk-fx5+) {meta} leaks and quasi-leaks for Firefox 5+

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