How To Keep Firefox From Getting Unbearably Slow

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firefox   How To Keep Firefox From Getting Unbearably Slow

I don’t like Firefox. I think it is a monolithic, huge, heavy browser, and its XPI-based architecture feels slow and dated. That said, it is much more open and customizable than Google Chrome, and I do feel that using an “independent” browser is good for the Web. I say “independent” because Google are giving Mozilla buckets of cash for being the default search engine, but still, that’s relative independence.

Also, at the end of the day, what matters most for me is performance. And while Chrome has a fast JavaScript engine and renders pages well, it would just freeze up on my system – becomes totally unresponsive and take almost a minute to “wake up”. Firefox, on the other hand, would gradually become slower and slower until it, too, would freeze up and choke. But since Firefox is more flexible, let me show you some quick techniques I’ve used to get around this and use Firefox in relative comfort (and responsiveness).

Memory Restart

firefox4   How To Keep Firefox From Getting Unbearably Slow

Above you can see that Firefox is taking up 977MB of RAM on my system right now. You can see that number thanks to a very handy add-on called Memory Restart. It shows you how much RAM Firefox is taking (and given Firefox’s leaky nature, I think this should be a native feature really). Once the number exceeds a threshold you defined, it becomes red (as you see above). Single-clicking the number restarts the browser and reloads all tabs. See what happens within seconds of clicking the button on my system:

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firefox8   How To Keep Firefox From Getting Unbearably Slow

Yes – you’re reading that right. 977MB turned into 327MB, and that’s with the same exact set of eleven tabs open, and after I waited for all tabs to reload. So we’re talking about a reduction of 650MB of RAM, just by clicking one button and waiting about 15 seconds. That’s 5 seconds before I can continue working, and 15 seconds before all tabs load. Why does that even happen – I have no idea, and I blame Firefox’s awful architecture and general portliness. But Memory Restart makes this problem much more manageable.

You will have to find your own threshold by trial and error, but even if you have 16GB of RAM that doesn’t mean Firefox won’t become slow once it consumes more than a couple of gigs. If you’ve ever been frustrated by Firefox’s slowness, this is the #1 add-on for you to try.


firefox10   How To Keep Firefox From Getting Unbearably Slow

Above is a screenshot I just took of Notice the “F” orb under the CNN logo? That’s Flashblock at work. Websites often use Flash excessively, and Flash takes up plenty of memory. Flashblock lets you reclaim your computer and decide for yourself which Flash you want to run. But you don’t have to click the Flash orb every time you want to run an animation (that can be a nightmare on a site like YouTube). You can just do this:

firefox12   How To Keep Firefox From Getting Unbearably Slow

Just click that once, and you’re done. Flashblock is smart enough to take embedded content into account: If you allow all Flash from YouTube, embedded YouTube video across the Web will start working. Indispensable, really.

AutoClose Tabs

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This last one is not a must-have, but it’s nice: AutoClose Tabs makes tabs grow “old” and then closes them after a while. Once a tab becomes old, its text color changes, so you can see it is up for closing. As you can see above, you get to configure the intervals. I experimented with 3 minutes and 7, but realized it’s too fast for me. 7 and 13 seems to be working well for my browsing habits. The add-on is smart enough to only count time while the browser is active, so if you have the browser showing a page off to one side, and you’re (say) writing a blog post in another window, the tab showing the page will not close (and nor will any other tabs on that window).

The reason I say it’s not a must-have is that I did not notice massive memory savings due to closing tabs. If I close a whole bunch of tabs after Firefox reached 900MB of RAM, the RAM count doesn’t really go down. So you can think of it mostly as a way to unclutter your tab bar, and maybe it has a slight impact on speed as well.

Final Thoughts

Firefox memory management is fundamentally broken, and I don’t know if it will ever be fixed (here’s hoping, anyway). Until then, these add-ons are good enough for me. Do you suffer similar problems? If so, what solutions did you find?

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74 Comments - Write a Comment


Danny Stieben

Cool plugins, Erez! Although I wish it’d happen, I doubt Firefox will eventually get rid of its memory leak, although the devs have been working on memory usage for a while now.

I also like the AutoClose Tabs plugin. It reminds me a lot of Tab Wrangler, a similar plugin for Chrome:



bs.. memory costs nothing these days. who cares if a browser takes a gig?
at the mom my firefox has been running for a month, 11 beta. mem usage is 620MB with sixty (60) tabs sorted out in half a dozen panorama boxes. No problem at all.
And of course this is on Linux platform.

Erez Zukerman

I don’t mind the memory usage itself — but why does it have to get so sluggish? I have 6GB of RAM on my system.



I tried Chrome(ium) for a while, and the lack of a Master Password (which Google has steadfastly refused to address), the limited nature of the addons (Adblock for Chrome is primitive compared to Firefox’s, and it takes TWO addons to do a simple digital clock in the browser bar! You’re limited to a single icon-sized area for an addon’s GUI!!!) make Firefox much better IMHO.

Firefox’s memory leaks and freezeups have gradually disappeared between versions 4 and 11, and should continue to improve.



You forgot that you can reserve a part of the ram for Firefox cache and make websites open with blazing speed.

Actually over at Lifehacker they did their browser benchmark and Firefox consumed less RAM on average than Chrome. So that isn’t completely true.


Why do people lie? They don’t even know how to “reserve a part of the ram for Firefox cache”, or they would tell you.

Just people wanting attention if you ask me. This guy does not know what he is talking about or he would have explained what and how you do what he thinks works best for firefox ram/cache. Just another big phony.


Kshitij Chawla

He is right about the Lifehacker tsts , i dont know about reserving ram, never heard of it.


Mark Levison

Firefox a memory pig? Really come checkout Google Chrome :-) 20 tabs open and 3.8 GB of memory is gone. Lucky my laptop has 8 GB otherwise Chrome would be the only app open.



Maiko Engelke

I know it’s not exactly the released product, but the Nightly and Aurora channels are actually a lor faster then the stable channel right now. You would probably be surprised by its speed.

Another tip would be to use Panorama more efficiently. Create tab groups with around 9 tabs, something reasonable.

My computer is old and I have more than 100 tabs open and separated in groups, and it’s quite fast. it takes some memory, but since Firefox consumes less memory than Chrome with a lot of tabs open in the case, I just can’t use Chrome anymore


Christopher Pepin

It doesn’t matter how much memory you have. Your computer doesn’t magically grow new processors when you add RAM so even with 16 Gb of RAM the computer can only process so much of it at any given instant.

Billy H

We are not rendering 3D animated films here, we are browsing the web! There is very little processing done with displaying web pages and running little scripts.

Maiko Engelke

That would be on the past, when computers didn’t have power. The internet has evolved too. Try browsing on IE5.5 to see your internet with low processing power.

Also, a browser is also an interpreter, so, not, only it has to process dynamic content, but it also has to do all that with a non-native language like CSS and JavaScript.


John Penland

Chrome and Firefox both use similar amounts of memory, however, Chrome just makes you feel better about it. Seriously, if you add up the memory usage, it comes out at about even.

Erez Zukerman

Right — I don’t mind the memory usage per se; I mind the sluggishness.



This whole post shows a huge ignorance of the current status of Firefox development. You need to familiarize yourself with the MemShrink effort:

It has been underway for almost a year and has made great progress. Some of the key points that come to mind are:

1. Doing what any ‘restart when memory usage is too high’ extension does natively. It’s known as the memory pressure event, I think. It doesn’t restart the browser, it cuts memory down with calls to the garbage collection routines.

2. The confession that the update from version 3 to 4 was a complete balls-up in terms of garbage collection and that has only achieved version 3 performance levels again in version 10. In other words, Firefox 4’s memory management was a massive backward step and it has only been overcome with the release of 10.

3. Extensions *are* a nightmare when it comes to memory performance. They often cause what are known as zombie compartments – where memory assigned to closed tabs will not be cleared until the browser restarts. This is slowly being addressed in a few different ways. See

Several add-on zombie compartments have been resolved, including:

UF Comment Board Tools
Long URL Please
HTML Desktop Notifications

So update now!

An enormous leak was found to occur with the McAfee’s SiteAdvisor so by all means, if you have that running, uninstall it immediately!

Unfortunately the new-style of extensions based on Jetpack make memory reporting per-extension more likely but still not perfect. Additionally Jetpack SDK was causing a zombie compartment itself for disabled extensions! LOL

Alas Firebug causes zombie compartments so if you’re a developer and have that installed, you’re screwed because Mozilla made the bizarre decision to ffocus on native dev tools instead of repairing the zombie compartments in Firebug.

You really should update your information before you write ill-informed reviews like this.

Andrea Ippolito

I totally agree.
Big fan of Memory Shrink BTW

Erez Zukerman

Many thanks for the informative reply, pd. I did come across the MemShrink effort when researching for the post, but an “effort” does not always equate “results”, and the stable version of FF at the time of writing (v11) had the exact issues I was describing. My information was up-to-date, and nothing you said shows otherwise.

Your reply pretty much makes my point, though: Flaws with the basic architecture of FF make managing extension memory almost impossible.

David Bobb

The latest firefox versions (10+) are quite fast. I work at a public computer lab and just updated the old firefox 3.5 installs (which were already quite zippy) to 11, and version 11 was every bit as fast as 3.5 — which is suprising as the computers are low specced, (Windows XP with 512MB of RAM). I believe that the problem lies more with faulty extensions and things like Flash (which is out of Mozilla’s control). One of the best suggestions, I believe is to not install 20 different addons, and just keep a few important ones on hand. As you wrote, Adblock and Flashblock are good starts.

Erez Zukerman

Well, that’s the thing: I disagree that addons are “out of Mozilla’s control”. If you code an application and don’t take care to sandbox extensions well enough, to me, that is faulty architecture.

Kshitij Chawla

I aree. Mozilla is working on that now. They have already made some improvements in handling addons running amok with memory.



Got a message saying they don’t work with Firefox 12.0



Didn’t know about Memory Restart, thanks for mentioning it. Flashblock looks like a nice add-on as well, will be using it from now on.




I think you are forgetting about Memory Fox plugin. That has worked wonders for me with Firefox.

Trying not to spam or brag, I have previously written about this plugin and how it reduces Firefox memory usage. You can check here if you have time.

Erez Zukerman

Right — but Memory Fox didn’t work with FF 11 when I was researching for this post. Thanks for the link!



Ugh…Neither the Memory Restart nor the Flashblock are compatible with v 12

Charles Krakoff

Flashblock does indeed work with Firefox 12.0 – I installed it yesterday and it works perfectly, though it doesn’t do much to reduce Firefox’s voracious memory appetite. Memory Restart, on the other hand, was a disaster. It put Firefox into a sort of loop, where the screen would flash on and off and alternate with other open applications, and it was hard to make it stop. I finally did, and restarted in safe mode and removed it (I did this a couple of times, even restarting the machine to see if this was a fluke: it wasn’t)



Thanks so much for telling us about Memory Restart and Flashblock. They both have been very helpful to me. I love your site. I’ve learned so much from it. Thanks again.

Erez Zukerman

You’re welcome Judy!



I have been using Chrome, and just downloaded Firefox to access an educational tool add on I read about. It is working much faster than Chrome on my computer!



These look like great Apps…problem is they are not available for FF 12.



Yes, Firemin is a definite plus. Using 1,096k at this time and have been online all morning. Ghacks has another post for SpeedyFox which helps.


ReĂ˝ Aetar

Well I do these steps

sync my data to Firefox server,

unstall firefox with all user preferences

Reinstall it and sync it back.. reinstall the adons (there is a adone for backing up addons also)

Erez Zukerman

Wow, that sounds like a lot of work. And for how long does that last?

Kshitij Chawla

Firefox can natively sync your addons too. You can reset firefox from Help>Troubleshooting, then sync the addons back. Takes 5 minutes max.


Chris Hoffman

Just a quick note: Firefox’s interface is technically XUL-based. XPI is the file extension used by Firefox add-ons.

Good post otherwise, though! I’m a Chrome user at the moment, but I love the idea of Firefox as an independent browser. I may well switch back, one day.

I think the most important thing is using fewer extensions, though. Those seem to slow any browser down.

Erez Zukerman

Right! XUL based, I stand corrected. Thanks Chris!



This app is amazing as my firefox too was using around 1 GB of memory. Now it tops out around 150 MB… It’s perfect.


thank you for link. Does this firemin works with Mac



Those numbers seem way out there to me. I have never had Firefox use that much RAM. Even on your restart the number was higher than I ever get on Firefox. Chrome on the other hand is a pig and I get those kind of numbers without even trying.

As for your comments on Firefox being a “monolithic, huge, heavy browser”, what browser is lighter? All the main browsers are heavier with the exception of Opera.

Erez Zukerman

Well, you answered your own question. :) Opera shows that it doesn’t have to be that way.


I said Opera isn’t heavy and lighter than Firefox but I don’t get bad RAM usage with Firefox, not like you report getting anyway.


Nope. You said they’re all heavier with the exception of Opera.



Memory Restart was more trouble then it’s worth. It caused FF to constantly freeze. Removing Memory Restart fixed everything.

Erez Zukerman

Interesting! What version of FF did you use? I use Memory Restart all the time.



with firemin, firefox memory leak is history

Mozilla team should learn from it!



Comodo dragon browser is a good browser with lots of facilities


Comodo Dragon is based on the open-source Chromium project that Google builds its branded Google Chrome on. It has all the same limitations as Chrome.



Firefox was a revelation after IE, but it grew fat even after I removed extras. In frustration, I moved to Chrome and have only missed ‘open new tab in the background’ (chrome does not natively have that option).
Your post suggests it has not yet improved. I would like to support an independent browser and hope it makes a radical comeback. Something that makes good use of Windows 8 would be nice.



Exactly that is why I had migrated to Chrome and now using WaterFox – a 64 bit fork designed for speed.



Sorry. I refuse to believe that Firefox is slow and heavy when compared to Chrome. I just did a test to compare FF to Chrome(the latest beta version of FF which is 12) and I opened the exact same tabs as I had in FF and Chrome consumed more memory. Interesting.


Coudln’t agree more. I used to have Chrome as secondary browser because FF, with all the addons I cannot live without, and the countless tabs I leave open freezes A LOT. But guess what? Chrome does the same, with no addons and 2 or 3 tabs. The culprit is always the flash plugin.


Same here. I’ve used FF since 1.0 Otherwise I use Chromium sometimes just for fun


tony kennedy

been a fan of firefox since 3.0 ha ha ha yes i would block flash crap and ad block helps too but people please remember that you can delete your cookies and other stuff thats not needed this helps me out a lot


I’ve used Firefox since version 0.7 (yes, < 1.0!) and its addons are one of the main attractions. Version 4.0 became somewhat unstable (freezeups and crashes), but it's been improving greatly. AdBlock and NoScript help keep pages trim and protect from malicious sites; there isn't a decent version of AdBlock for Chrome, and IE? Forgettaboutit!



The aurora build of Firefox is much faster. I’ve been using Aurora for quite some time, and surprisingly, it has not crashed as of yet. For the RAM issue, you can edit about:config to disable cache in memory:

browser.cache.memory.enable -> false

This will decrease performance for the browser unless you don’t use cache at all.



Memory Restart sounds fantastic! Nice post by the way.

Erez Zukerman

Thank you, Jessica!


SEO Training Pune

Thanks for letting me know about Mozilla. On my system, Mozilla keeps on crashing twice a day. Nice info. I have downloaded the Restart Memory add-on and will try if I face this problem



Thanks I will give it a try.


I do not agree.

My firefox is using 160 megs of ram at point of writing and it has never used more than about 300 megs. I have a total of 6 addons installed.
Maybe you are just using the wrong addons + plugins, there is no way firefox is using 977 megs of ram unless you are doing something wrong.


You have to understand that not everyone surfs the same sites you do. I regularly have over 10 tabs open in 2 instances of FireFox and it blows WAY past 500MB of RAM. Java, Flash, etc. make a huge difference when you compare it to a basic website with not much going on.

I do not agree.

Sometimes I have more than 40 tabs open and it still doesn’t reach 400 mb of ram. Java, Flash etc are *plugins*, so it’s not Mozilla Firefox that is at fault here.


Dave LeClair

Easy solution, I use Chrome.


Peter H

I’ve been flipping back and forth between firefox and chrome as my default browser. I finally gave up on both and have switched to opera, which I find has none of the problems of the other two. I still use firefox for specific tasks such as editing my webpages. And of course, IE8 is still on my taskbar as well.


yea same wid me…now using opera…it works gr8 :D :B


I used Firefox from when it was called Phoenix, but since Mozilla’s accelerated release cycle the Firefox browser has rapidly become slow and sluggish for me. The “memory leak” has been around for years, and I can’t say it uses much more than any other browser. Opera is my main browser because at the moment it’s the nicest browser for daily use IMO, but I also load IE, Firefox, Chrome for different purposes.



Firefox has helped convince me that there is a huge disconnect between programmers and users. It’s as though the two have entirely different goals. The users want something that works, while the programmers want to experiment. But surely they can keep their experiments on their own machine until they actually work, (I know. “Don’t call me Shirley.”)

I started using Firefox six years ago. I had over 30 extensions. It was fast.

Today I have nine extensions. Firefox has doubled in size and has become a memory nightmare.

Solution: I switched to Opera this week. All they need to do now is come out with “Opera Slim” for folks who don’t need a “Suite”. Nah, everybody needs a “suite”, right? RIGHT!?!?

Erez Zukerman

Actually, RIGHT!!! :)

I fully agree with your Opera Slim idea. I don’t know how practical it would be for them to implement it, but personally, I’m dying for something like that. A browser with a modern, fast, JS and tab engine, that just -works-.

That would be revolutionary.

(Actually, some would say IE9 comes close… but let’s not go there)



I’ve solved the problem of excessive comsumption memory thanks to the Fox Memory addon. Now my Firefox v.11.0 takes only 30 to 160 MB


Craig Walsh

Ive been using IE9 and it is WAY faster than Firefox.
I never liked IE but it blows Firefox and Chrome out of the water.
I dont know why! But it works.

Erez Zukerman

I’m glad it’s working for you! That’s excellent :)


Kshitij Chawla

Firefox is making very powerful inroads into performance and memory management. I use Aurora(15) and it rarely slows down on me nowadays, apart from the periodic chrome hangs which afflict this alpha channel. Most of my problems were due to too many addons. I disabled a bunch of them and its pretty responsive now and doesn’t go into gradual decline.
Apart from that, there’s also an about:memory page built into firefox which allows you to manually reclaim memory. Why don’t you try that out, see how well it works for you?

Another addon- suspend background tabs, also helps a lot. Additionally, firefox is implementing click to play features. Once they are fully baked out, that should help too.

Let me know of your experience with these suggestions.

Erez Zukerman

Thanks for these excellent recommendations! Th next time I find myself using Firefox and feeling a slowdown, I will try these out.



Firefox is sluggish. It runs heavier than many software with high specs. The solution I found is to close down Firefox, then it won’t be sluggish since it would have to be running to be sluggish.

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