Firefox Memory consumption MemShrink

“Reset Firefox” is wonderful

TL;DR: Please recommend the “Reset Firefox” feature to anyone who complains about odd, persistent performance problems and/or high memory consumption.

In Ars Technica’s article about the Firefox 19 release, carbon fibre made a comment complaining about Firefox’s performance.

Firefox still doesn’t fix memory issues and smoothness, at least on my experience. It’s constant random jerks and extreme mem usage, until restarted. I use chrome but I have been wanting to switch FF for awhile, but I can’t, as long as they fix these issues, long standing issues since ver. 4.

There were four notable responses.

korg250 (my emphasis):

They are losing market share by not fixing the memory issues. Even on my 8GB SSD i5 system I have to restart it when it reaches over 1 GB because it starts to slow down A LOT. And it get over 1 GB very fast for someone who constantly open/close tabs like me (even in safe mode).

I was an avid FF user until I saw myself installing an add-on to restart FF when it reaches X MB of memory usage. Today I use Opera for most of my browsing but I some sites does not work properly with Opera and some extensions only exist on FF.



Do you have extensions installed? Maybe one of them is causing it.


every benchmark I saw, firefox uses less memory than everybody else, I really don’t get why people complain about it?


You might have problems with your profile. Visit about:support, and click on the “Reset Firefox” button in the top right corner. It’ll generated a new profile that preserves much of your browsing history, though it will disable any add-ons you have. (It’ll give you details about exactly what it preserves and discards before doing so, so you can cancel it if you change your mind.) This step fixes a lot of performance problems like the ones you describe.

To summarize the responses:

  • Me too!  It sucks.
  • Are extensions to blame?  (A reasonable question, though less likely since Firefox 15 fixed most extension-related leaks, and one that can be difficult to answer conclusively.)
  • Really?
  • Is a busted profile to blame?  Try “Reset Firefox” to determine if so.

carbon fibre didn’t respond, but korg250 (the “Me too!” commenter) took up the commenting baton…

korg250 (again):

In my case it is not about memory usage, but how slow it becomes when it reaches 1 GB of usage.

I will try the about:support tip listed before.


Out of curiosity, which version of Firefox are you basing this on?

Because the thing about these “I used Firefox until X got too much for me, and I switched” kind of imply something quite significant, which is “I am no longer using Firefox, and can therefore not speak for the possible improvements that have happened since I switched”.

For the last couple of versions, Firefox has shown extremely good memory usage in my experience. And yes, they were absolutely horrible at this in earlier versions, and I’ve been *that* close to switching a number of times because of it. I’ve ranted a lot about how their memory usage was just so broken I doubted they’d ever be able to fix it. But in my experience, they have.

(And yes, this is 120% subjective, and I am certainly not arguing that if your experience differs then you are wrong. But I have noticed a vast improvement in recent versions. As I recall, the first of these fixes started trickling in around the FF13 timeframe, but I could be wrong on that.)


I think you’ve some other computer issues. Here is my system, 2.4gig firefox process. Still running fine and dandy no slowdown, this is 18 mind you.

korg250 (again):

I am always in the latest version. Was using 18.0.2 until today. Now I am on the 19 after resetting via about:support (still watching how it goes).

Maybe my installation had something wrong and even after the updates the memory issue remained – I don’t know. But I made the “switch” over the last week, when I compared speed between FF and Opera.

korg250 (again):

The reset via about:support worked for me. My FF is running smoothly for over 24 hours. Thanks guys!


Many people have used Firefox for years, and so the chance of mysterious profile problems occurring are quite high.  “Reset Firefox” cleans that dirty slate.  As the support page says, it will “easily fix most problems”.  It’s a simple, one-shot process with a high effectiveness rate that can be explained in a single sentence — perfect for mentioning in an online forum.  (Indeed, I should have linked to the support page in my comment, and then I could have written less explanation.)

Ideally it would also be tried by anyone who tries switching back to Firefox from another browser.  In fact, if Firefox is started up for the first time in a while (3 months? 6 months?) it would be great if it offered to automatically do this.

34 replies on ““Reset Firefox” is wonderful”

To be honest, I’m probably one of those guys who’d have left for Chrome if I weren’t ideologically opposed to it and I never even gave Reset Firefox a chance because I wasn’t aware it’d tell me what it was and wasn’t going to keep.

I figured that it’d only be useful if my Firefox blew up so badly that I already had to laboriously migrate all the things Reset wouldn’t know about or wouldn’t trust. (Last time that happened was the migration from 3.6 to 4.0)

I guess I’ll try it as soon as I can get around to writing that migration script. (I use a lot of esoteric about:config tweaks I can’t live without, Greasemonkey scripts and Stylish styles I use in place of extensions to try to unify all the “Are we applicable to this URL” on-load handlers, saved sessions, hundreds of unloaded tabs in my Tab Groups view, etc.)

…maybe once Addon SDK is in Aurora and enough of my addons have stopped bundling it for me to know what effect that had on memory consumption.

What would be wonderful is if we were more thoughtful when adding more persistent state. Right now it’s super easy to add a new pref and get a review without putting a lot of thinking into whether it could be a hazardous piece of persistent state that could lead to the kind of problem that ‘reset firefox’ is meant to address.

Chrome has an explicit policy of keeping persistent state to a minimum. We don’t.

I tried to raise that issue on dev-platform but didn’t make my point clear enough so wasn’t listened to.!topic/


This has been something I recommend in comments since it was released and I couldnt agree with you more. No other short piece of advice can so quickly cure so many firefox ills.

I have hope that firefox will eventually one day self recommend this to users when it detects persistently poor performance.

There is some behavior (two crashes in a row?) in which I believe Firefox recommends the reset.
(Someone please feel free to correct or confirm.)

I don’t fully understand what the reste button does, but whatever it is, why can’t firefox be doing it (cleaning up after itself) all the time?

Seems like a bit of a hack that hides the true problem.

Definitely a hack, but an effective one. Solving the true problem is extremely difficult.

The reset Firefox function is a workaround and easy solution for a user but the real reasons for profile problems should be fixed.

Corrupt sqlite or other database files could be the reason for issue like this.
And then we have the preview images that never got deleted or probably gigabytes of pending crash reports which will never deleted.

SInce about FF15, memory usage of Firefox has not been a problem for me. Smoothness has been problematic, though.

I never knew that “Reset Firefox” did that. I never considered using it, as I thought a “Reset Firefox” function would wipe out all my profile data. And if I wanted to do that, couldn’t I just create a new profile?

Put another way, I think that feature is badly named.

Maybe “Rebuild Firefox Profile” would be a better name? Something that suggests that you keep your user data, but it’s re-created from a clean slate.

This feature is of most use to the more casual users of Firefox, who probably aren’t aware that their adware infested toolbars could have some impact upon performance. Naming this feature “Rebuild Firefox Profile” would be too cryptic. I highly doubt most Firefox users are even aware of what a “profile” is.

It was definitely designed for less technical users. The question is whether it can be made more useful to advanced users without compromising its simplicity.

I recommend reset ff to all my friends when the problem is non-trivial. Works a treat nearly every time. Specially for those people with 5+ years old install and zillion of “adware” put stuff in the ff configs.

But then the problem reappears again after some heavy usage of the browsers. It is a bit like Registry in the old days on Windows 98 and XP. So yes it really is a temporarily and effective hack.

I think Mozilla should force a Profile Reset, going inline with every ESR Release, or possibly every 6 months. ( So Normal Release Cycle will get 2 reset per year while ESR will get reset every year or every ESR released. )

This should be done while the Installation of version update is happening.

And i think i can tell why the browser slow down after using 1GB or higher. The Memory usage, assuming no massive memory leaks since memshrinks, suggest the user is using multiple tabs heavily, In today’s web we get insanely large amount of JS running, from Multiple Analytic on a single page, JS Forum, Multiple Ad Network , JQuery or Other Frameworks, Multiple Social Network. All these are extremely common, and these are on a single page! Imagine 10 – 30 Tabs Web page each having one set of these opened.

Then there is the memory fragmentation issues you told me earlier. Which means after some comparatively heavy, and long browsing sessions Memory are stuck in high level. Although i assume this will be fixed when GGC lands ( or not? )

And i forgot to mention, one of the solution to the too many JS is to use NoScript or Ghostery. Personally i keep the Ads running since blocking ads is would have stop the site from generating revenue. But By not having as much JS running Firefox is much better at handling large amount of tabs.

Again, Fixing this would properly require SupperSnappy or e10s ( Since i heard SuperSnappy has been ditched )

Just upgraded to Firefox 19 in a Linux Machine and the Reset Firefox option does not appear in about:support. Any ideas why?

I have used Firefox for years with the same profile, as I find it the best browser.

However, recently memory has been higher than expected, 400-500Mb with only a couple of tabs, e.g facebook and gmail, bbc news open, and pages were becoming a bit sluggish to load.

I just Reset Firefox and my memory usage for a similar set of tabs is around 220Mb now. It also seems more snappy too 🙂

Thanks Nicholas. I have followed Memshrink (and Snappy) for a while now and it is making a huge difference.

This is an awesome tip. Never heard of the feature before.

I agree with the comment that Reset Firefox is a bad name. Call it something like “Repair Profile” or “Clean Profile” perhaps.

There are two reasons why I’m hesitant to use the reset feature:

1) The wording of the confirmation dialog suggests that there is no way back if it doesn’t help.

2) As far as I can tell from googling around it will not restore the currently open windows and tabs, which is somewhere between “extremely annoying” and “no way” for me.

Of course you can go back to your profile before the reset by manually creating a backup of your profile folder. Regarding currently open windows and tabs you should use the session manager extension which is extremely useful.

The trouble for me with this feature is that I have tweaked a dozen or so settings in about:config (mostly disabling various privacy-invading features) and I certainly don’t remember exactly which settings I changed.

Why not you check “about:support” to look for important modified preferences which you changed and by clicking on Status column button in “about:config”

Zlip: The list in about:support has hundreds of entries, and the list in about:config (user set) has thousands. I recognise a few of the settings in about:support, but I have no idea if all the settings which I consider important to keep are in there.

about:config only has maybe 2-3 hundred prefs. The bold ones are modified, so that is all you need to look at.

Any reason why only the default profile can be reset? I browse using both Aurora and Nightly, with different profiles, as I am a web developer. However, I let my wife use the stable release only.

I have been running nightly for the past four years and the reset is a feature which I would love to use regularly.

This would be much easier to use and recommend if it imported sessionstore from the old profile as well. I made a copy of my old profile before doing this (I was expecting it to make changes to the profile, not create a new profile and delete the old one)

Im a bit stuck with a huge browsing history -because when you wipe old history it badly messes up the url autosuggestions. This seems to be because the history can only be ordered according to ‘first accessed’ date, so urls which are frequently visited get wiped nevertheless , and then to compound the problem, for some reason they dont get reinserted in the autosuggest dictionary on subsequent visits, perhaps they are eliminated by the presence of similar first accessed but deeper urls, not sure but its messed up.
I couldnt find any addons to manage the history better, considering running a custom query on the sqlite db when i get the time to fiddle it out myself.

I tried a reset just to see how it would go. Took well over 2 hours to get things back into a working state.

Have to: export settings of all addons that can do so; record settings of any others, where feasible; get a copy of the about:support page for a reference of installed addons and changed user prefs.
Then reset.
Then: set standard options; update user:config options; reinstall addons; import old addon settings; copy over certain custom files (Stylish database, FireFTP connections, Session Manager sessions, etc); and just plain rebuild stuff that you can’t find old settings for (eg: Chatzilla); and of course re-customize the interface.

Telling someone to just reset their profile seems fine for anyone working with a plain vanilla install, but would be a potential headache for anyone with a fair number of customizations. Though, I’ll grant it’s better than just creating a new profile and trying to copy stuff over, since it does retain some of the more important information for you.

I appreciate the effort you’ve gone to. Have you noticed any improvements with the new profile?

Not really. I’ve never used the Reset before, but I have created new profiles and copied stuff over a few times. It’s been about a year since the last move.

As far as performance, I’m still having significant load time issues (which I think is related to things like AdBlock and NoScript which have to review the page contents before display). Resource Monitor’s reported working set for Firefox is just over 800 MB for a single day’s use (and has crawled up to 900 MB in the time I’ve been writing this, reset to 830, and started climbing again). about:memory shows 575 MB of explicit allocations, 440 MB of javascript allocations, 120 MB of windows objects. That’s with about 100 tabs open (and maybe two dozen used?), though is still a bit higher than usual.

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