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Firefox uses too much memory (RAM) - How to fix

Firefox sometimes uses more memory (RAM) than it should. This can make Firefox slower, and in extreme cases, it can even make Firefox crash. This article describes how to make Firefox use less memory.

  • Depending on your operating system, you can review and monitor memory usage through specific tools. On Windows, the Performance tab of the Windows Task Manager displays memory usage.
Note: If you send performance data, Mozilla will gather data including the memory usage for your Firefox, which will help make Firefox better for future versions.

Updating to the latest version

The latest Firefox version includes improvements about memory usage. Update to the latest version.

Extensions and themes

Disabling memory consuming extensions and themes

Extensions and themes can cause Firefox to use more memory than it normally would.

To determine if an extension or theme is causing Firefox to use too much memory, start Firefox in Safe Mode and observe its memory usage. In Safe Mode, extensions and themes are disabled, so if you notice a significant improvement, you can try disabling or uninstalling extensions.

Hiding intrusive content

Many web pages have content you don't really need that uses memory to display (see the plugin section below). Some extensions allow you to block such unnecessary content:

  • Flashblock allows you to selectively enable and disable Flash content on websites.
  • NoScript allows you to selectively enable and disable all scripts running on websites.


Plugins to display special types of content can consume large amounts of memory, especially older versions.

Updating your plugins

To check to see if you have the latest versions of all your plugins, go to our Plugin Check page.

Disabling memory consuming plugins

You can test to see whether one of your plugins is causing Firefox to use too much memory by selectively disabling some of them:

  1. Click the menu button New Fx Menu and choose Add-ons. The Add-ons Manager tab will open.

  2. In the Add-ons Manager tab, select the Plugins panel.
  3. Click on a plugin in the list to select it, then select Never Activate to disable it.
  4. Repeat for some of the plugins in your list.

After disabling some of your plugins, close and restart Firefox, and observe its memory usage. If you don't see an improvement, you can enable those plugins again and try with a different set.

If you do see an improvement in Firefox's memory usage after disabling a certain plugin, you may leave it disabled. If you can't because its use is widespread on Internet, try to find an alternative lighter plugin.

Checking Flash hardware acceleration

For certain plugins that play videos such as Flash, the content rendering in full screen can be accelerated by hardware. It eases memory usage in case of a dedicated graphic card memory.

  1. Navigate to a page that shows a Flash video.
  2. Right-clickHold down the Ctrl key while you click on the video player and click Settings… in the context menu. The Adobe Flash Player Settings screen will open.
  3. Click on the icon at the bottom-left of the Adobe Flash Player Settings window to open the Display panel.
  4. Check Enable hardware acceleration is selected.
  5. Click Close to close the Adobe Flash Player Settings Window.

Checking Firefox hardware acceleration

Firefox hardware acceleration eases memory usage in case of a dedicated graphic card memory.

Restarting Firefox

Firefox's memory usage may increase if it's left open for long periods of time. A workaround for this is to periodically restart Firefox. You can configure Firefox to save your tabs and windows so that when you start it again, you can start where you left off. See Restore previous session - Configure when Firefox shows your most recent tabs and windows for details.

Using fewer tabs

Each tab requires Firefox to store a web page in memory. If you frequently have more than 100 tabs open, consider using a more lightweight mechanism to keep track of pages to read and things to do, such as:

Other applications using up memory

Having many applications running simultaneously may cause your computer to run slowly and other applications to as well. By closing down some of the unnecessary applications, memory usage will be reduced.

Memory troubleshooting tools

  • Firefox:
    • The about:memory page allows you to troubleshoot finely specific issues about memory (for instance, caused by a website, an extension, a theme) and sometimes its Minimize memory usage button may help you instantly reduce memory usage. For guidance on use of about:memory visit about:memory
    • RAMBack lets you flush many of Firefox's caches, allowing you to distinguish caching from leaking.

      Even if you're not a C++ programmer, you can try your hand at some of the tools and tips Firefox developers use to debug leaks.
  • System:
    • View how much memory is being used by checking with the Task Manager. Visit How to use and troubleshoot issues with Windows Task Manager at Microsoft's support site. Once you are at this Microsoft article, go to "How to monitor your computer's performance". This will explain the performance tab information and more.
  • System:
    • View how much memory is being used by checking with the Task Manager. Visit See details about your computer's performance using Task Manager at Microsoft's support site. Once you are at this Microsoft article, click on "Get details on how much memory is being used" under the instructions. This will explain the performance tab information and more.
  • System:
    • View how much memory is being used by checking with the Task Manager. Visit Windows 8 Task Manager at Microsoft's support site.

Add RAM to your computer

If you exhausted all tips in the previous sections and your memory usage is still close to the maximum, maybe it's time for you to add more memory to your computer. RAM is cheap and will provide a huge performance boost.

Based on information from Reducing memory usage - Firefox (mozillaZine KB)

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I am running XP SP3 on an old Toshiba Satellite 5005 laptop with 512meg RAM

During the last couple of months I had repeatedly experienced extreme slow response followed by sudden FF crashes (I let Firefox report a few of them back to you)

I am in the habit to always keep Windows Task Manager running to find clues as to what might be causing problems and had noticed that slowing usually started at some point after the PF-memory usage exceeded the 512meg actual RAM, crashes seemed to happen when PF usage exceeds 600meg after I quickly clicked on several control surfaces (buttons, scrollbar, etc. in background windows?)

Opening multiple windows in FF seem to consume morePF- memory than opening multiple tabs in only one window, so I keep only one window open with several tabs active (usually no more than half a dozen) and I am wondering if my use of "Undo Close Tab" causes pages not (never) to get released again, explaining the PF-memory never getting released again (even after I open a second, empty window, closing the first with all the open tabs), forcing me to close and restart FF to "get a new, clean start"...

~100 add-ons are installed (active are <20 are, assuming that the inactive ones do not lead to a shortage of critical resources which might cause the slow-down or crashes).

Until yesterday I was using FF 3.6.12 , today I updated to FF 3.6.13 (as suggested) and am under the impression that it uses more memory (leading to problems sooner).

I didn't want to wait until the problems show up again and decided to look into reported high memory usage problems in the support pages (a) to try to confirm my assumption that the high number of installed but inactive add-ons aren't a problem (b) trying to smarten up a little on problems of the current FF release(s).

searching for "High Memory Usage" info I ended up here:

and find listed in the "Memory troubleshooting tools" section the recommendation to install "Leak Monitor" (which I did) and "RamBack" (which I didn't install after reading the comments made by dissatisfied users). I'd like to suggest that you review those and consider to instead recomment "Click&Clean" as the critic there did...

with friendly greetings I'm off trying my luck with FF 3.6.13 using only about a dozen add-ons (including "Leak Monitor" and "Click&Clean")

Onwards through the fog...


p.s.: I hope I get a CC of this emailed to me; I hate making a comment and then not having a copy of what I had written...  ;-))

See /forums/knowledge-base-articles/706489 for related discussions about this article.

Hi WernerU, Click&Clean does the same things as the Clearing Recent History menu and doesn't address the high RAM memory usage.

I reject this request.

It is bound to be controversial, but it is very clearly related to the subject of memory usage. And has been the subject of a lot of recent development work. The other discussion threads are both locked, one above and one on the KB forum

I have added a short paragraph to the article.

I did not even bother changing the info above my edit that relates to OS memory tools

Scoobidiver, I did not want to edit your work directly, but maybe bothersome or annoying are better words to use. Further I guess that if using such add-ons reduces memory usage, the content is getting blocked rather than just hidden, so possibly consider re-wording slightly:

Hiding bothering bothersome content

Many web pages have content you don't need such as ads and that uses memory to display (see the plugin section below). Some extensions allow you to hide block such annoying bothering content:

  • Adblock Plus allows you to hide ads on websites.
  • Flashblock allows you to selectively enable and disable Flash content on websites.

The about:memory page is intended to help Mozilla developer troubleshoot when a user file a bug and doesn't help to reduce the memory usage. Putting it as the second section as it was THE solution to reduce the memory usage is misleading. One sentence in the troubleshooting section could be added, but that's all.

I agree with your remarks about renaming the section to Blocking bothersome content.

Thanks for the response scoobidiver,

I think in the near future this is going to be THE solution, and is going to eclipse using OS specific or other tools (otherwise the developers will be rather disappointed). But I do agree my comments would be controversial in the context of a KB article. At least putting in a sentence mentioning it would help. I shall leave that to you.

My points in favour of mentioning about:memory are

  • In some instances using the buttons on about:memory WILL reduce memory usage
  • About:memory does help to point the finger at the problem, often emphasizing a particular application or tab is the problem and that must be beneficial if it deflects direct criticism of Firefox; and as such maybe it is a good idea to include in a KB article.

I fixed some minor things and added a small sentence about the about:memory page at the end. It needs review.

Ok, probably such links are considered techie and not suitable for the main kb article, but maybe those of you troubleshooting problems with memory will find this recently added MDN article useful: Zombie compartments the article also include a link to an explanatory blog about compartments


Sorry, in the section called Using fewer tabs can we also suggest to use Tab Groups?

See also:

On my computer, Firefox uses much more RAM memory if Adblock Plus is enabled. It should be removed from the article.

Thanks for posting this. I removed AdBlock Plus from the "Hiding intrusive content" section since, like you said, it can increase memory usage.

Related bugs:

  • Bug 988266 - Very high style-sets memory usage with AdBlock Plus
  • Bug 1001426 - 150MB memory usage spike by enabling Adblock Plus

The MDN etc documents have been revised and consolidated.

There is now a proper guide to use of about:memory, and a list of tools and tips relating to memory & performance.

I have review pending on edit /kb/firefox-uses-too-much-memory-ram/.../85852

P.S. Approved by joni, Thanks

The "Memory troubleshooting tools" section should be updated to include information for Windows 10. I set up a "Needs change" entry.