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Firefox 4 seems to have a memory leak.

  • 85 replies
  • 1752 have this problem
  • 1 view
  • Last reply by jajones

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I have used Firefox 3.x for some time on a XP machine. Never any problems. It is a machine that I keep running for weeks on end without rebooting. It is a workstation but rather old.

After upgrading to Firefox 4 I get problems with memory. The machine has 2Gb of RAM. I have four tabs open in FF4, about the same as I usually have had in the past. Two of them are now pinned.

When I reboot Firefox it take about 90Mb. But after half a day that is up to 400Mb. I open and close tabs during the day. After another reboot cycle memory usage is again down.

Looks like a memory leak.

I have used Firefox 3.x for some time on a XP machine. Never any problems. It is a machine that I keep running for weeks on end without rebooting. It is a workstation but rather old. After upgrading to Firefox 4 I get problems with memory. The machine has 2Gb of RAM. I have four tabs open in FF4, about the same as I usually have had in the past. Two of them are now pinned. When I reboot Firefox it take about 90Mb. But after half a day that is up to 400Mb. I open and close tabs during the day. After another reboot cycle memory usage is again down. Looks like a memory leak.

Modified by NoahSUMO

All Replies (20)

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I have also experienced this problem recently. Today, when leaving FF up for an hour or so, I returned and noticed that the computer was incredible slow and laggy. After a painful 3-4 minutes taskmanager finally opened and I saw FF eating 3 Gigabyte of my memory.

Seriously, where is the fix?

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That's funny. I liked to have fallen out of my seat.

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If you do have problems with Firefox4 or Firefox 5 memory leaks there is probably little point in posting in this thread.You may get many agreeing with you that there is a problem.

However imho posting in a long meandering thread like this one will not get anyone investigating and fixing any alleged Firefox problems. You will need to post hard facts with full details of reproducible memory leaks if you want to be in with a hope of websites, extension developers, or Firefox developers investigating anything.

Read any advice in this thread, but you probably would do better to start your own thread. You may be interested in my post upthread: /questions/799397?page=2#answer-185195

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We should BEG the good graces of Firefox, and HOPE they might pity the over 1200 and some who have echoed each other in this thread?

I'm beginning to see the root cause of this Firefox problem.

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Quickly reading through this again, I note

  • facebook was mentioned, apparently that is a known problem with facebook, that will also affect other browsers, and hopefully facebook are looking into.
  • I did list upthread some details about problems being investigated and changes being made to try to solve Firefox problems.
  • at least one user has said changing to Firefox 5 is an improvement, something recommended after he started detailing his problems.
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I do not use Facebook, thus it could not have caused the issue on my machine. And, I have doubts about whether a website can cause a browser memory leak. That should not be possible.

A link to a blog talking about the long litany of Firefox memory issues does not restore any confidence.

After so recently upgrading to 4.0, which was supposed to be a stable, consumer ready, version, I'm not very open to the suggestion of upgrading again, to what is a beta/incomplete version, as a solution to the original problem, which is the mistake of upgrading to 4.0 in the first place. Each upgrade takes me further away from 3.6.17, a version I know is reasonably stable.

In this thread, on this Firefox help forum, I would like to hear someone say YES we understand there is a problem. We get it. We believe you. We're doing our best to investigate and fix the problem. What you contribute here on this forum is helpful. Please continue doing so. We will announce a solution within this thread as soon as we have one.

PS... And please be patient because we're tired of screwing up and want to get it right this time.

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I think everyone agrees Firefox 4 has memory problems, and that some of those should never have got out into a release version.

I think users who do have memory problems are tending to be advised to either, revert back to Firefox 3.6 or upgrade to firefox 5.0

What I as an ordinary user am saying is that Mozilla and the developers track the Bugs including memory problems on Bugzilla, and often comment about them elsewhere.

I would be almost unheard of for you to get comment direct from anyone from *Firefox* in this thread on development issues or bug fixes, that is not the purpose of the support forum.

All I can do is point to other articles, or make suggestions that may help. Apparently because of this new short release cycle bug fixes are being made in firefox 5 rather than firefox 4.

Firefox 4 is not due any more releases, other than if any essential security fixes are required. Firefox 5 is now in beta, and scheduled for full Release I believe on 21st June 2011by which time Firefox 6 will be on the the Aurora channel and firefox 7 will be on the Nightly channel. ( details of the planned schedule see figure )

If you wish to provide feedback that you do not like the problems you now have a button on firefox to do that or use link : http://input.mozilla.com/en-US/feedback

If you wish to help those trying to fix problems report specific and reproducible details of problems, that will entail quite a bit of work. ( the most obvious bugs will have been identifies if not already fixed in firefox 5).

The facebook problem is described in this 42 comment as I mentioned above, and that particular bug 635121 is apparently only remaining open until confirmation is obtained that facebook have fixed it. From what I understand particular websites can cause memory problems, as can use of some firefox extensions in certain situations.

Modified by John99

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I think everyone agrees Firefox 4 has memory problems, and that some of those should never have got out into a release version.

I have heard very little acceptance of responsibility, and a lot of blame for everyone else.

I think users who do have memory problems are tending to be advised to either, revert back to Firefox 3.6 or upgrade to firefox 5.0

I think the great majority has reverted back to 3.6.

* see also Installing a previous version of Firefox

It's not difficult to install an older version. That's one saving grace in this whole mess.

What I as an ordinary user am saying is that Mozilla and the developers track the Bugs including memory problems on Bugzilla, and often comment about them elsewhere.

So you're kinda like the resident self-appointed Firefox apologist? Again, evading a problem that is obviously real just agitates the situation further.

I would be almost unheard of for you to get comment direct from anyone from *Firefox* in this thread on development issues or bug fixes, that is not the purpose of the support forum.

Then what is the purpose of this forum? Is this not SUPPORT.mozilla.com? Where is the SUPPORT part? We're supposed to be satisfied with, pacified by, user-semi-expert-apologists?

All I can do is point to other articles, or make suggestions that may help. Apparently because of this new short release cycle bug fixes are being made in firefox 5 rather than firefox 4.

Firefox 4 is not due any more releases, other than if any essential security fixes are required. Firefox 5 is now in beta, and scheduled for full Release I believe on 21st June 2011by which time Firefox 6 will be on the the Aurora channel and firefox 7 will be on the Nightly channel. ( details of the planned schedule see figure )

Because of this "new short release cycle" you point out, I have zero interest in any future releases of Firefox. I will not upgrade to an incomplete, poorly done, product that is being rushed into release with severe defects. Please understand, this FF4 memory thing is not just "a little bug". It is a glaring, egregious, screw-up.

If you wish to provide feedback that you do not like the problems you now have a button on firefox to do that or use link : http://input.mozilla.com/en-US/feedback

I'm providing feedback at support.mozilla.com, with no results. Why would I care to chase down another website when this one should have been more than enough. If Mozilla is interested, they can read their own support forum, here, where we're posting now. If they are not interested in that, I'm not interested either. It's their product we're talking about, not mine. I will not beg them to pay attention to their own customers.

If you wish to help those trying to fix problems report specific and reproducible details of problems, that will entail quite a bit of work. ( the most obvious bugs will have been identifies if not already fixed in firefox 5).

There is already plenty of information in this thread for Mozilla to recreate the problem, in several different ways. How hard is it to simply watch the behavior of your product on 64-bit Win7? I mean, really, people are now posting videos on YouTube demonstrating, proving, the FF4 problem...

YouTube Video

Are you telling me Mozilla is oblivious of how to recreate the problem? Really?

I think they're more likely hiding from the problem.

The facebook problem is described in this 42 comment as I mentioned above, and that particular bug 635121 is apparently only remaining open until confirmation is obtained that facebook have fixed it. From what I understand particular websites can cause memory problems, as can use of some firefox extensions in certain situations.

This is what I'm talking about. Let's blame a website or an add-on. It's their fault, not ours...

The browser should not be allowing a website or add-on to create such problems in the first place. Do you see any website creating such a serious problem in IE? Of course not. And, if it were to happen, Microsoft would promptly fix their browser. Even Microsoft, as bad as it often is, would not blame a website for its problems.

I'm seeing a very dark horizon looming for Firefox. The path they are on, the attitude I'm sensing, will continue to cause pain for all involved. And, because the end user will tend to avoid such pain, other browsers will gain market share.

Within just a year or two, the makers of Opera and Google Chrome could end up with a huge gift from Mozilla, most of its current Firefox customer base.

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Because of this "new short release cycle" you point out, I have zero interest in any future releases of Firefox. I will not upgrade to an incomplete, poorly done, product that is being rushed into release with severe defects.

Really, jumping to conclusion much?.. just think of Firefox 5.0 as a minor major release like it was Firefox 4.1 with no real feature additions or such. If anything it may end up being like an improved version of Firefox 4.0.*


The main purpose of support.mozilla.com was for the Knowledge Base and then the forum. This forum is a users forum and one cannot expect Mozilla to spend all day here providing support. Some do on some subjects like mobile Firefox.

Modified by James

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FF4 is significantly different from FF3, and FF3 from FF2, and so on.

And, yes, I have indeed jumped to the conclusion FF5 will have significantly different/new features while old, inherent, problems like being a memory hog will continue virtually ignored, glossed over, dismissed as minor, and blamed on everyone else including the end user.

Why should I not believe that?

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Which shows you do not follow the development and is just guessing at best. There have indeed been bug fixing of some of the issues. If fact some futures that were originally targeted for Firefox 5.0 did not make it as it missed the cut off date as they wanted to keep things moving along smoothly and work on what does exist easier.

As for versions there was no Fx3 as there was Fx3.6, Fx3.5 and Fx 3.0 before the Fx 2.0

Modified by James

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Reading your argument, I think you're drunk. In fact, I hope you are because the alternative is much worse.

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James's comments make good sense to me, and for what it is worth, there are mainly minor changes, and some fixes between Fx4 and Fx5 . There are not big interface & feature changes. (I have used Fx5 for a while and am typing this using Fx5)

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Next best thing, find a workaround. This is NOT coming from Mozilla, and was helpful to me: http://annoyances-resolved.blogspot.com/2011/05/mozilla-firefox-4-memory-use-leak-fix.html

Thanks for the link, Sherry. Firefox would not be a very good browser, where it is in popularity, without all of the add-on support it receives. FF has been very lucky to have so many loyal third-party entities who continue to fix Mozilla's mistakes and omissions.

Just yesterday, I found an add-on called "Tab Control" for FF 3.6.17. It is a BIG help to those who like to have a lot of tabs always open. It reduces the size/width of all tabs down to that of a would be "pinned" tab. Now, all of my tabs fit within the screen width I like to use, without having to "right-click + pin" every new tab. Tab "pinning", for size purposes, was the only thing I cared about in FF4.

Another add-on I have been using in FF3.6 for a long time is "Menu Editor". It became necessary because of how Firefox is so predisposed to opening new windows instead of tabs.

In my opinion, the base model of FF is so lacking and poorly conceived it would be unusable without add-ons. Add-on developers, rather than Mozilla's programmers/developers, are the heart of Firefox, the real FF we use. As it seems, Mozilla is more interested in keeping the add-on makers busy than actually improving/evolving their product.

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James's comments make good sense to me,

Yeah, I'm sure he does make good sense to you...

and for what it is worth, there are mainly minor changes, and some fixes between Fx4 and Fx5 . There are not big interface & feature changes.

I don't think you can be sure of what the final release will have in it.

Still, if so, you're saying 5 is little more than a bug-fix or service pack to 4. Is that sound development protocol? Seems to me, Mozilla could be trying to play catchup in terms of version number, IE9, rather than make good innovative product.

(I have used Fx5 for a while and am typing this using Fx5)

I'm typing this using FF 3.6.17 and, thanks to add-ons, I'm not missing/wanting a thing.

John, I understand you love FF and fiercely defend it but it's okay to be upset with Mozilla when they make a mistake. I'm upset because I too like FF. Being a blind apologist accomplishes nothing. In fact, it is a disservice to all FF users.

If you are/were not experiencing the FF4 problem, why are you here. How could you possibly offer any answers while not knowing, or even originally believing in, the problem?

Your steadfast solution is to sweep the problem under the rug with an upgrade to the beta project version. That is simply not a good answer.

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If I have no memory problems it does prove for some users there are no problems. In fact I would think for most users there are no problems. Many problems are likely to relate to extensions or site use. Some of you may find it more useful to help figure out exactly what combinations cause problems, so that someone can fix them.

I do not know what the final release of Firefox 5 will have, but I think the idea is to have it as the current version that of 5 that is now in Beta , unless some major unexpected problem occurs leading to a feature having to be removed. As James was saying ignore the number change think of it as an improved Firfox4.

By the way; those of you on Firefox 4; have you tried looking where your memory is going by keying into the location bar about:memory. If you do that on Firefox 5 the data breakdown is even more detailed and on Firefox 6 and 7 you also get buttons to clear and minimize memory usage (assuming they make it to the release). The developers are working on many fixes and improvements to Firefox, and that definitely includes its memory handling and reporting.

It is not easy to have it both ways

  1. masses of additional extensions to firefox
  2. and at the same time firefox working with all these extensions without problems

I'm typing this using FF 3.6.17 and, thanks to add-ons, I'm not missing/wanting a thing. You will however be missing any bug fixes and security fixes introduced in later versions , that may not be included in 3.6. Support for 3.6 may not last as long as expected with the rapid release cycles.


By your own reasoning why are you in this thread about firefox 4, if you use firefox 3.6 , and have no intention of trying firefox 4 or 5 unless forced to.

Modified by John99

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John, your argument has now become as bad as James', and I don't have time to beat my head against your wall. I repeat for the last time...

Everyone using FF4 has the same problem because you cannot blame a website or add-on for these issues. That's a cowardly cop-out.

You DO NOT know what the final release of FF5 will have in it, so stop acting like you do. And, PULLLEASE, do not even presume to talk about FF6 and 7. You are so ridiculous.

It does not matter how many or how few add-ons there are. Mozilla controls the platform upon which all FF add-ons are developed, and they have total control over how their browser interprets web pages. Stop crying about add-ons and websites already.

I'm happy with FF 3.6 for the foreseeable future. Version 3.6.17 is about as patched, security wise, as it can be. New releases introduce new security concerns, not the other way around. Your understanding of software exploitation is poor.

The end user looking at "about:memory" output will solve ZERO problems. Mozilla needs to look at THEIR problem and fix their browser. That is all.

Lastly, you are a typical self-appointed message board wannabe-expert. In reality, you offer very little substance. I am here, on this forum, to show my dissatisfaction with Mozilla, and to counter the nonsense from people like you.

Have a nice weekend. My conversation with you is over.

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Hope you have a nice weekend too.

My Firefox 4, 5, 6, and 7 are starting a happy weekend, with no memory problems today, even if I run two versions simultaneously on a legacy machine but then I do not have many extensions installed. I wonder if that is a clue. It certainly could be if anyone considers trying to troubleshoot a Firefox memory problem.

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I've noticed the problem is exacerbated with Facebook - specifically whenever facebook is running a game (and therefore opening the plugin process). Completely kills my computer.

I just got rid of firebug to hopefully help the issue, but it really is a problem for me that occasionally my entire computer just seizes up because FF is taking up 96% of the available memory - what is it DOING that it needs that much power? Looking at a single web comic, my email, and playing a browser-based game that has a chat associated with it.

That's just ridiculous.

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