Firefox memory leak? It doesn’t have one. Unfortunately, because of the way it’s configured to run out of the box it *looks* like it has one.
Follow these simple steps to get your Firefox memory usage under control.
These configuration changes are a trade-off between internet browsing speed and memory usage. They are most useful if you are multitasking and need Firefox to be less of a memory hog while using other applications.
#1: about:config
Type “about:config” into your address bar to access the hidden configuration options for Firefox.
#2: browser.cache.memory.capacity
Controls how much memory is used to cache pages.
Right click on the page and choose New then Integer and create an integer called browser.cache.memory.capacity and set it to a low number. This controls how many kilobytes of memory are used for the browser’s cache.
NOTE: number in screenshot is too small. Aim for 80% of whatever the default is.
#3: browser.cache.disk.capacity
Controls how much disk space is used to cache pages in kilobytes.
Set browser.cache.disk.capacity to between 5000 or 15000.
128MB to 512M -> 5000.
512BM to 1GB of RAM -> use 15000
#4: config.trim_on_minimize (optional)
Configure Firefox to swap memory to disk when minimized. This will make Firefox less responsive if you minimize/maximize a lot, but it is good if you need to free memory while multi-tasking to other applications.
Right click on the page and choose New then Boolean and create a boolean called config.trim_on_minimize and set it to true. Now when you minimize the window it will free up memory.
#5: network.prefetch-next
Network link prefetch will download all pages with the rel=”prefetch” tag. This uses up more memory than you would otherwise think.
Set network.prefetch-next to false.
#6: browser.sessionhistory.max_total_viewers
This controls how many pages of history are kept in the back/forward buttons. Lower the value to something acceptable. If you do not use back/forward often then you can set this very low.
Set browser.sessionhistory.max_total_viewers to a low number.
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Further Reading
Ryan at CyberNet installs 200 Firefox extensions (via Rooster) and checks memory usage. It jumps from 145 MB to 195 MB after two hours (note that this is a worst case scenario).
Mozillazine article on reducing memory use in Firefox.
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45 Comments
This is really useful! Thanks!
Awesome blog, great article. I added it to my blogroll, hope you don’t mind. I really like what you were able to do with Sandbox - if I do not have to purchase the CSS upgrade to mod it, I may switch over myself.
Thanks symbolik.
It’s comments like yours that keep this fun to do.
The CSS upgrade was a *lot* of work (I’ve never used CSS before), but it was more satisfying than dealing with a pre-packaged theme and the issues most of them have.
Only I can manage to screw this up. I managed to create a key with String instead of Integer for the first one, and now I can’t change it! ggrrr.
Thank you - excellent tips and all in one page.
Added to my ff settings. :)
Wow, your firefox hack is awesome. I kept watching firefox use more and more memory till it finally would crash. Very annoying and I couldn’t find a solution anywhere. Then, once I noticed how much memory firefox would use when it was active for awhile, I realized it was a memory leak. A little googling and then I discovered this blog. What a difference it’s made in Firefox’s performance. Muchas Gracias for sharing this knowledge.
I’m glad you found it useful. It really is essential to getting Firefox to work.
I’m suprised this isn’t better known - even among the incredibly IT-savvy people I know, they see this memory leak as an insoluble problem. I’m looking forward to sharing this article with them, as the “memory leak” is probably the most-publicized Firefox fault.
Many grateful thanks!
The other big cause of memory problems with Firefox is Flash… but I think that was fixed in the latest Flash update.
Of course, all of these settings, while they will reduce memory usage, will do so at the cost of speed. Caching more results will make pages load faster. If you have the RAM to space, you might not want to make these changes.
Can’t you also change the cache settings from Tools/Options/Privacy…or is that different from tweaking them in about:config?
@alan:
Tools/Options/Privacy is for clearing the cache. About:config is used for setting values for disk/memory cache.
Different things.
There’s a problem with #2. You say “This controls how many megabytes of memory are used for the browser’s cache.” But on the Mozilla site here (http://kb.mozillazine.org/Browser.cache.memory.capacity) it says this value is kilobytes.
@Michael:
Thanks for that. Corrected.
thx a lot man.
it’s all, see ya.
Thanks for the suggestions.
Can you offer a better suggestion for #2 other than “80% of the default”? If this is a new key, I don’t know what the default is. Something like what you have done for #3 would make this excellent list even better.
Thanks
It is utterly ridiculous that a user should have to go through that many steps to get Firefox’s memory “under control.”
OR you can just change:
browser.cache.memory.leak
from 1 to 0
I hope you like looking at that huge number of unused memory in the Task Manager.
@Jon: The defaults are as follows. Use a smaller number.
Physical RAM Memory Cache (in KB)
32 MB 2048
64 MB 4096
128 MB 6144
256 MB 10240
512 MB 14336
1 GB 18432
2 GB 24576
4 GB 30720
8 GB and up 32768
@JoeB: “I hope you like looking at that huge number of unused memory in the Task Manager.”
Did I need to prefix this article with “only apply if you’re having memory problems”? I run a VM-Ware linux machine on my desktop that uses up all available memory. I like to keep Firefox opened for quick reference, but I want to free the memory for VM-Ware when Firefox is minimized.
engtech…thanks for the reply, but I’m still confused. I’m using Firefox 1.5.0.9, and under Tools/Options/Privacy there’s a box where I can manually set the number of MB of disk space for the cache. Is that different than using about:config? Thanks.
I submit that your VMWare problem is special and that ordinary Firefox users have plenty memory to spare on caching. I can’t fathom why someone would sacrifice usability for a large amount of free and unused (!) memory.
Presenting these hacks without clearer caveats does everyone a disservice.
@Alan: That’s for disk cache, so it may be the same as #3.
@joe: This is a guide for people who have memory issues with Firefox, not a guide for people with a large amount of unused memory.
If your tips are so good then why doesn’t Mr. Firefox include them by default? I smell something fishy here.
Thanks - I’d been having a memory leak problem, hopefully this will do the trick.
Heh, there’s nothing fishy about this. Back before Firefox was “a gleam in someone’s eye”, Mozilla (the browser) had a similar but opposite issue. When you maximized a browser window after having it minimized for some time, it took a very long time to come up. Searching their forums way back then, I found the solution: add “config.trim_on_minimize” to about:config and set to false. These days most people have much more RAM to allocate, so the devs take advantage of that, by default.
You can’t just type some random thing and have it affect the browser. Firefox has to recognize the entry, and if it does, that means it was designed to.
It would be nice if they would put some sort of easily accessible Advanced Settings panel in so users could make changes to suit their preferences regarding memory usage. But given the average user, they probably feel it’s best to keep these settings hidden.
I made your requested changes and saw memory usage drop by about half. However since I made the changes firefox crashes on me 2-3 times per day. Since almost 90% of my work involves the use of ff I guess I am going to go back to original settings. I am using the latest version of ff and it is (unfortunately) running on windows crappy (i mean xp). Has anyone else had crashing problems after making the above changes? did you solve them with out reverting to the original firefox settings? Thanks for any help or tips.
THANKS!!!
Thank you for your great tip, my firefox works great now!!
My firefox never crashes but it does use over 150MB if left un touched for hours and hours. Thanks for these tips, I hope they help
I have noticed that excessive CPU usage by Firefox occurs in conjunction with excessive memory usage. The “MultiMeter” downloadable sidebar gadget for Vista is helpful in monitoring this. I currently use Firefox 2.0.0.3, and it has the setting “browser.cache.disk.capacity,” but not the option “browser.cache.memory.capacity.” Anyone know why this is missing?
PS: May I suggest that your blog entries should have dates attached to the titles?
Hi,
thanks for all the tips, I am having memory issues with firefox, it seems to “hang” at times and doesn’t react to tab changes or when writing something it just stops….
I applied the above “hacks” but the trim on minimize doesn’t seem to do anything…. I am around 200 mb, the about:config shows that I have set true for this but still, when I minimize it doesn’t go down a bite! (I have restarted firefox and even the PC completely) Do you have any idea why this doesn’t work?
just another big thank you. :) FF was hitting 400 MB of memory in Windows and in Linux. With the combination of tab-mix plus, the tab-close-undo option, FF’s memory, and running ~20 tabs. I knew what was causing it but didn’t know where to fix it — now I do.
i don’t use firefux.it has so many
security flaws it looks like a piece of swiss cheese
150??? Christ, I’d *love* that! Mine was using 880Mb today Eight hundred and eighty.
@ Gilbert Wham:
One person I know regularly complains about GIGs of memory being eaten up by Firefox.
The good news is that Firefox 3 (out soon) fixes most problems.
Thanks for this! Firefox was up to 1,400 MB today. I was getting fed up with it. I work with ColdFusion and Dreamweaver, don’t know if the constant refreshing, multiple CSS and JS includes make it worse. But I’m very happy to see that it’s been addressed.
@carmen schmidlap & maybe others
what is it you don’t like about swiss cheese? most of them don’t have any holes at all, so it may just look as you don’t know what you’re talking about. and considering the holes iexplore definitely has, it’s all about chosing a software that suites your needs and doens’t ruin your computer as soon as you have it running (or installed? sorry if you’re running windows, because then it seems you don’t really have much of a choice or do you?)
ps: yes I’m swiss. and I love good cheese. and maybe some people should stop eating crap that comes out of cans that only have “cheese” written on the label but has nothing to do with the real stuff (this also applies to chocolate-flavoured strawberries, blue chocolate and bright-red-but-tasteless tomatoes). if you quit buying this crap, well maybe they’ll stop selling it. oh yeah, this also applies to software.
When I did this, my Firefox MB usage shot up to 70MB! Is that supposed to happen?
Wow, thanks!
so clear and fast!
now i`ve gotta do it to the rest of the office heheh
Gracias compadre!
@ Richard Watt:
At this point I would just wait for Firefox 3.
Firefox 3 will fix this memory problems.
I found an great to get your ram usage to 30,000mb.
go to the about:config screen like always,now find these two codes and turn them to false.
look up this: network.http.pipelining.ssl
network.http.pipelining
now reboot your browser and e-mail your results to me at
evan93333@yahoo.com
You are awesome! My firefox works now. I don’t mind donating to a site like this. I am very happy.
Thank you.
Wow!
Nice tips, thanks for sharing
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