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I can have just one Firefox instance open, open to a site like Google or Stack Overflow, and see it consuming over 600,000 KB of memory. This seems excessive. Is something fishy going on here? Is there something I can do to keep it from doing this?

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What add-ons do you have installed? – Hello71 Jul 22 '10 at 18:29
300mb. From a browser. Is that even much? Opera eats about 1.5gb sometimes. Chrome is the same. 300mb is nuffin. 600mb is also REALLY low. Now, when they throw 4gb modules at you.. I don't think 600mb from a browser is a lot. – Shiki Jul 22 '10 at 19:16
1.5 gb? Jesus... – Abe Miessler Jul 22 '10 at 19:19
@Shiki: Something's wrong with your browsers, I think... Mine never exceed 500MB for any browser. :) But either way, when you have a bunch of other programs like Eclipse open, and maybe a virtual machine as well, 600MB starts to matter. – Sasha Chedygov Jul 22 '10 at 19:20
Yeah, 500k is the max that I usually see and that's with a million things open that require a lot of resources. – Abe Miessler Jul 22 '10 at 19:22
up vote -1 down vote accepted

Firefox has been know to have a small memory leakage problem.


  1. Open Firefox and go to the Address Bar. Type in about:config and then press Enter.

  2. Right Click in the page and select New -> Boolean.

  3. In the box that pops up, enter config.trim_on_minimize. Press Enter.

  4. Now select True and then press Enter.

  5. Restart Firefox.

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This is interesting. I found this resource which advises on "config.trim_on_minimize" You may find it useful. Regards, – Xavierjazz Jul 22 '10 at 19:10
Alright it's hovering at about 300,000k right now. I'll let you know how it goes long term. – Abe Miessler Jul 22 '10 at 19:13
This doesn't actually speed up the browser. What it does is makes it so that when you minimize Firefox, its memory gets dumped to the hard drive. This means that when you restore the window, the memory has to be loaded back up, which is a relatively slow process. However, it does not actually reduce the amount of memory used; it just dumps it to the hard drive (which is obviously much slower than RAM). – Sasha Chedygov Jul 22 '10 at 19:18
Wouldn't everything else on my machine run more smoothly if there is 600,000k extra floating around tho? – Abe Miessler Jul 22 '10 at 19:21
@Abe Miessler: Perhaps, but again, this is only when Firefox is minimized. If that's what you want then go for it, but personally, I don't feel it's worth slowing down the browser for. – Sasha Chedygov Jul 22 '10 at 19:23

Try it also:

1- Fetch only pages that you click

Firefox mostly resembles to Google from this point of view. It has a built-in feature (enabled by default) that will pre-download the pages behind the links it thinks you MIGHT click. Google anticipates you might click the first result from the page, but how in the world can Firefox anticipate the link you’re going to click? Anyway, in my opinion this is just useless bandwidth usage, CPU power and HDD space. You’re practically downloading and storing pages you are not viewing. Here’s how you stop that in three simple steps.

In the about:config list, filter up your search after ‘network’ so it would be easier for you. Then, find through the remaining list options the key that says network.prefetch-next. It should be set to TRUE. Double click it, and it will turn to false. There we go, now Firefox will stop acting creepy and will only fetch what you click ;)

2- Limit the RAM usage

Although it’s not taking up THAT much memory as other browser, shortly, it still does. But you have a way to control that. It’s just a simple configuration setting and you’ll get the numbers to be more comfortable. Filter up your search after “browser.cache” and select browser.cache.memory.capacity from the remaining options. I believe the default setting goes all the way up to 50000, but there’s no need for that. You have to adjust the value depending on the amount of RAM memory you have installed. For RAM sizes between 512MB and 1GB, start with 15000. For RAM sizes between 128MB and 512M, try 5000, and you will be happy of the result.

3- Reducing the RAM usage even more when Firefox gets minimized

I got an extremely low usage on this one. Somewhere around 10MB, so it’s definitely a must-do. Basically, this will move Firefox to your hard drive when you minimize it, and as a result it will take up much less memory. It won’t even go back to the same high usage after you restore it. Even if Firefox will be located in your HDD instead of your RAM, I can assure you the restoration speed will be the same, with no delays.

All you have to do is right click your about:config page, select New and click Boolean. A box will appear and you will have to enter config.trim_on_minimize as value. The boolean value should be set to TRUE in the next screen, and that’s it. Test it after restarting Firefox.

4- Make pages load faster

Most browsers are configured for dial-up users. Tweak the settings for your optimal use. Filter out the list after “network” then search for the key that says network.http.pipelining and set it to TRUE. You may alter the key below (network.http.pipelining.maxrequests) and change it into a higher value - 10 for example. Voila, your pages will load much faster now.

This is just about it, and if you guys have any other tricks for improving the Firefox experience, we’ll be glad to hear them.

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To eliminate add-ons, disable them in safe mode and see how much memory is being taken up.

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I recently started experiencing this problem, along with total freezes. For me it was totally solved by just disabling plugin-container.exe using instructions found at

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I tried many ways since I started using Firefox, and none of them actually worked. So, I usually just restart it when it's slow.

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