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Problem: Memory Leak. Firefox usually on a Mac, OSX; reaches 2-3 GB of RAM -- heap-unclassified -- very quickly (~10 mins)



This is a problem reported in another long thread and the thousands viewing that indicate it is a major concern, and continues in Firefox 23 not just the Firefox 20 from the report.
Original thread title: Version 20, Memory Leak Still? Original thread Link https://support.mozilla.org/en-US/questions/958108

I am one of the forum moderators, and do not have this problem myself. Unfortunately I do not even have a Mac.

I am trying to make information easily findable. I have started this thread with two aims

  1. To provide links to any
    • Known workarounds or solutions to this or related problems
    • Separate related threads (because it is always best and in accordance with forum guidelines to deal with only one person's problem per thread )
  2. To collect information on the problem that may help developers. Particularly steps to reproduce this or closely related problems.

In this Thread

  1. The next post down is an index of such links.
  2. The post after that is a summary of the information or help I would like from you if at all possible.
  3. Then extracts from related threads.

PLEASE NOTE, because I am trying to keep this as a tracking and cross linking thread I am reserving the right to heavily edit or delete any post in this thread as I see fit.
I am intending mainly to keep content in separate threads with only summary, extracts and links in this thread. Feel free to post in this thread with definite solutions or to mention any thread you consider relates to this problem.

This thread is NOT going to deal with any issues involving Flash Player.

Additional System Details

Installed Plug-ins

At least initially you need to test with no plugins enabled, and in Firefox's safemode.


  • User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:24.0) Gecko/20130731 Firefox/24.0

More Information

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Question owner

Index to Linked Articles and Threads

Knowledge Bases etc

Other Links

Your Operating System
Note Firefox Knowledge base articles should display information related toyour own OS with an option to view other versions of the article. Mozillazine articles usually cover all OS within one article.

Other Threads

  • It all started from this thread Version 20, Memory Leak Still?
  • This is a Windows thread [xxxx]
    (If the number of Windows related threads or comments increase I will spin that off as yet another tracker, so far I am aware of this user and only a single unknown user reporting a very similar problem) See [under]

Topics Under Investigation The title of the topics may be subject tochange as investigation progresses.

  • Bug 896016 - Investigate why Firefox reaches 2-3 GB of heap-unclassified on OSX very quickly (~10 mins)
    • see under xxx possibly reproducible on pay for site xxx
    • probably not yet generally reproduced but see xxx under
  • Bug 893943 - Webpage conflict causes Firefox to become nonresponsive and requires manual termination of process in Task Manager.
    • see under xxx

Modified by John99

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Question owner

Help Wanted

(Noah or other mods feel free to edit this thread as required)

The primary issue is

Bug 896016 - Investigate why Firefox reaches 2-3 GB of heap-unclassified on OSX very quickly (~10 mins)

If you see this issue on the any particular site and you have accessed the site with all plugins disabled, and preferably from a clean additional profile please start your own thread about the issue using /questions/new then post back here to confirm you have done that. We know of one particular site causing this problem, but it is pay for access, so identifying another site may be helpful, and will also indicate other sites are affected. Possibly this sort of problem will most likely be seen when accessing large databases.

Initially you need not worry about whether it is in fact heap-unclassified. If you get any large and rapid increase in memory usage of that sort of order (2-3 GB RAM in 10 minutes) something is seriously wrong and we will be interested.

As a secondary issue if you get similar problems but with only a single add-on enabled please also start a new thread then post back here. We may also be interested in other cases where memory usage is going over 2-3 GB even if not that rapidly.

  • This does not apply to Flash Player.
    • it has too many issues.
    • they are hard to investigate
    • we certainly need to segregate Flash Issues from other problems
  • as an aside note Flash Player hang reporting is being improved with testing already live on Aurora https://wiki.mozilla.org/Socorro/Hang_Processing_Proposal
  • This does not apply to Ghostery 5.0.1, that is a known issue and you need to upgrade.

These are the suggested steps for those wishing to demonstrate this problem, from

Visit about:memory as soon as you open Firefox and before you begin any browsing. Then, copy and paste everything on the page to http://pastebin.com and return to this site and give us the url to the pastebin.

Then grab another copy of the about:memory data during the halfway point of 10 minutes. Or when you notice you've reached the halfway point of the memory leak (if the highest you've seen is 2GB for example, then get the about:memory @ 1GB).

And lastly, get one more copy of the about:memory data before Firefox becomes unresponsive but is near the 2GB (or whatever) high memory you speak of. This part will be tricky if Firefox is hanging. :/

So you should have about 3 pastebins worth of about:memory data when you're done and I will show that to the memory dev and report back on his findings.

It'd be nice if you could just paste that data here but the first part of it becomes mangled & unreadable due to how the "Main Process" data section is formatted. See my example attempt here: https://support.mozilla.org/en-US/questions/963890#answer-456894

Cyberpawz 0 solutions 27 answers

Helpful Reply

Being the originator of the original post that has birthed this post, I would like to mention that this issue was originally brought up at version 4, and again at version 20.

That is the version 4 query.

That being said, I hope this finally can be resolved, because this seems to be a problem that has been ongoing for quite some time.


  • Added thread title as link anchor
  • Added link re Fx 4 problems in other thread ~j99

Modified by John99

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Question owner

Version 20, Memory Leak Still?

As Cyberpawz mentions above this was noticed in Firefox 4 then Firefox 20.

The entire Original Post from Cyberpawz relating to Firefox 20:

I've been using Firefox since well, lets just say long enough... Version 20 for the Mac seems to not have fixed any bugs or memory leaks.

One of the "fixes" is to restart Firefox, which is the only "fix" that works, but this really isn't a fix, this is a stopgap situation, in where you release the memory by closing it...

Are there other people with this same situation? My Firefox uses with nothing in the main page except google.com, if it's open for over 24 hours over 1GB of ram... 2 GB in 48 hours, etc...

The most Firefox has ever used was 5GB before I shut it down, now I know, restarting Firefox seems to stop this from happening, but as I said, this is a stopgap, there is something inside Firefox that makes this happen.

Is there anything in the future that will fix this issue, or is Firefox going to be forever a Memory Hog worse than Microsoft Office?

Noah posted in that thread Extra thought: If you have a large store of anything, I think that can contribute to the memory problem. For example, having 500+ bookmarks saved or 200 downloads saved in the download history or having 800+ cookies saved or having 100+ passwords saved and so on. You get the picture.

posted a general solution usually expected to resolve the issue

Cyberpawz was running Ghostery
at a time when it transpired that Ghostery caused a leak but apparently has continuing problems after updating that.


Other than on one particular site I am not yet aware of anyone able to reproduce this problem and willing to try in safe mode in a clean profile with all plugins disabled and then produce the about memory results that would help developers.

has kindly participated in filing a bug for this article,
but AFAIK that only has information and steps to reproduce and about:memory information in relation to the problem occurring on a single specific site.

I am not aware of the problem being demonstrated with data for other sites. (No doubt Noah or curmudgeon99 will correct me if that is wrong)

Firefox 21.0 on OS X 10.8.4 still has a memory leak that occurs with no Add ons, 1 tab and leads to 3GB of memory usage in 10 minutes.

This is a thread by curmugeon99. It may contain useful general tips & links. But has no resolution for curmugeon99

memory (Windows)

This thread resulted in a bug being filed, and at the moment is the only thread I am aware of where Windows has similar problems.