Why is Firefox using so much memory and how to fix it?

Milan Stanojevic
by Milan Stanojevic
Deputy Editor
Last update:
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  • If Firefox is using too much memory, it might be clogged by extensions or unnecessary settings.
  • Another reason for Firefox consuming too much memory is intrusive content or certain scrips.
  • So to cut on Firefox RAM usage, you will need to check and tweak several browser settings.
  • In the end, if all these don't solve the Firefox high memory usage problem, try a lighter browser.
how to fix Firefox memory issues on Windows 10
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Firefox is one of the most popular web browsers on the market. However, Firefox has its issues and many users report that it uses too much memory on their Windows 10 PC.

This can be a major problem, so today we’re going to show you how to fix it.

Why does Firefox use so much memory? Sometimes, it’s a matter of an outdated browser. Also, the issue is commonly triggered by corrupted data or too much cache.

Extensions and certain browser values also affect how Firefox behaves on your system, so we’ll look into these too.


How do I control Firefox using too much RAM?

  1. Switch to a different browser or upgrade your RAM
  2. Update Firefox to the latest version
  3. Start Firefox in Safe Mode
  4. Switch to the default theme
  5. Disable all extensions
  6. Disable specific plugins
  7. Hide intrusive content
  8. Restart Firefox
  9. Close unnecessary tabs
  10. Close other applications
  11. Use about:memory feature
  12. Change Firefox settings
  13. Reduce memory usage when Firefox is minimized
  14. Change browser.sessionhistory.max_entriesvalue
  15. Change browser.cache.disk.capacity value
  16. Use Firemin

1. Switch to a different browser or upgrade your RAM

If none of the previous solutions work, you might want to try using a different browser. Some PCs can’t handle Firefox, so be sure to try an alternative browser.

That is why we are recommending that you choose a lightweight alternative called Opera. This web browser uses the Chromium engine and features one of the lowest memory requirements of all web browsers.

It has an extremely modern UI that you can further upgrade using the built-in settings, and even go beyond that thanks to the extensive add-on support, allowing to specialize the browser in whatever direction interests you most.

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2. Update Firefox to the latest version

  1. Click the Menu button in the top right corner and click the question mark icon at the bottom.
  2. Click About Firefox from the menu.
  3. A new window will now appear. Check if Firefox is up to date.
  4. If your version is outdated, Firefox will download the latest version automatically.

After updating Firefox to the latest version, check if memory issues still persist.


3. Start Firefox in Safe Mode

  1. Click the Menu icon in the top right corner.
  2. Now, click on the question mark icon and choose Restart with Add-ons Disabled.
  3. When the confirmation message appears, click on Start in Safe Mode.

You can also start Firefox in Safe Mode with a useful keyboard shortcut. To do so, be sure to close Firefox completely first.

After that, you can start Firefox by doing the following:

  1. Locate Firefox shortcut on your desktop.
  2. Press and hold the Shift key on your keyboard and double-click the Firefox shortcut.
  3. If the confirmation message appears, choose the option to start Firefox in Safe Mode.

After starting Firefox in Safe Mode, check if the problem still persists. If memory problems are gone, it means that your configuration or a third-party extension is causing problems with Firefox.

Disable extensions one by one and see how the browser behaves. Hopefully, you’ll find the problematic plugin in no time.


4. Switch to the default theme

  1. Click the Menu button in the top right corner. Choose Add-ons from the menu.
  2. Go to the Appearance tab and make sure that Default theme is selected.

After selecting the Default theme, restart Firefox, and check if everything is working properly.

Many users like to customize Firefox with new themes. Although some themes look visually impressive, they can use too much of your memory.

To fix this problem, it’s advised you switch back to the default theme and check if your memory usage changes.


5. Disable all extensions

  1. Click the Menu button in the top right corner and choose Add-ons from the menu.
  2. Navigate to the Extensions tab. A list of all installed extensions will appear.
  3. Click the Disable button next to an extension to disable it.
  4. After doing that, restart Firefox.
  5. After Firefox starts again, check if the problem still persists.
    • If the issue is resolved, you need to go back to the Extensions tab and enable extensions one by one.
    • Be sure to restart Firefox after enabling each extension.
  6. After finding the problematic extension, disable or remove it, or download the latest version.

Users had issues with Ghostery, Skype Click to Call, Greasemonkey, and dictionary extensions. If you’re using these extensions, we advise you to disable them and check if that solves the issue.

If you don’t use custom Firefox themes, you might want to disable third-party extensions. Extensions can often cause increased memory usage and in order to fix it, we advise you to disable all extensions.


6. Disable specific plugins

  1. Click the Menu button and choose Add-ons.
  2. Go to the Plugins tab and select Never Activate for a specific plugin. Restart Firefox.
  3. After Firefox restarts, check if the issue still persists. If the problem isn’t resolved, try disabling a different plug-in. (After finding the plug-in causing memory issues, be sure to enable all other plug-ins except that one.)

In addition to extensions, certain plugins can cause memory issues with Firefox. To fix the problem, you might want to try disabling certain plugins.

If you need to use that specific plug-in, be sure to update it to the latest version and check if that solves the problem.


7. Hide intrusive content

hide intrusive content

Certain web content can be quite demanding on your resources and in order to prevent high memory usage you might have to hide it.

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According to users, certain scripts can be quite hungry in terms of resources so you’ll have to disable them. To do that, you’ll need to use third-party extensions.

The NoScript extension will allow you to choose the scripts to disable on specific websites.

Keep in mind that disabling certain scripts can affect how some websites work, so choose carefully which scripts you disable.


8. Restart Firefox

You can temporarily fix this problem by restarting Firefox. Some users reported that Firefox memory usage can increase if the application is running for prolonged periods of time, so be sure to try this solution.

While this is a temporary workaround, it should work for most users.


9. Close unnecessary tabs

Each open tab increases the amount of memory Firefox uses. If you tend to have more than ten tabs open at all times, you might experience certain memory issues.

In order to improve performance and fix this problem, we strongly advise you close unnecessary tabs and keep only the ones you need open.


10. Close other applications

Open tabs in Firefox will increase your memory usage, but other applications can also contribute to this problem.

Some applications can be quite demanding on your resources and that can leave less memory available to Firefox.

If you’re having any memory issues with Firefox, we recommend that you close any demanding applications running in the background. By doing that, you’ll free your memory and improve Firefox performance.


11. Use about:memory feature

  1. In the Firefox address bar, enter about:memory and navigate to that page.
  2. On this page, you can view detailed reports regarding memory usage.
    • You can also free your memory with ease.
    • To do that, click Minimize memory usage button in the Free memory section.

12. Change Firefox settings

  1. In the Firefox address bar, enter about:config.
    • If you get a warning message, choose the proceed option.
  2. A list of options will appear. Find these specific options and change their values like so:
    • browser.cache.memory.capacity to 0
    • browser.cache.memory.enable to false
    • browser.sessionhistory.max_total_viewers to 0
    • browser.tabs.animate to disable
    • browser.sessionstore.max_concurrent_tabs to 0
  3. After making the changes, restart Firefox and check if the problem is resolved.

In addition, you can also try changing these options:

  • javascript.options.jit.chrome to true
  • javascript.options.jit.content to true
  • content.notify.backoffcount to 5
  • network.dns.disableIPv6 to true
  • network.http.pipelining to true
  • network.http.proxy.pipelining to true
  • network.http.pipelining.maxrequests to 8
  • plugin.expose_full_path to true
  • ui.submenuDelay to 0
  • network.http.proxy pipelining to true
  • security.dialog_enable_delay to 0
  • browser.download.manager.scanWhenDone to false

13. Reduce memory usage when Firefox is minimized

  1. In the Firefox address bar, enter about:config.
    • A list of options will now appear.
  2. Now, you need to create a new option.
    • To do that, right-click on the list below and choose New > Boolean.
  3. Enter config.trim_on_minimize as the name and click OK.

  4. Set its value to True and click OK to save changes.
  5. Restart Firefox and check if the problem is resolved.

If this solution doesn’t fix the problem, you can remove the newly created option or simply disable it.


14. Change browser.sessionhistory.max_entries value

  1. In the Firefox address bar, enter about:config.
  2. When the page opens, enter browser.sessionhistory.max_entries in the search bar at the top.
  3. Double click browser.sessionhistory.max_entries in the list of results and change its value to 5.
  4. Click OK to save changes.

  5. Restart Firefox and check if the problem is resolved.

15. Change browser.cache.disk.capacity value

  1. Create a new tab and enter about:config in the address bar.
  2. Enter browser.cache.disk.capacity in the search bar at the top. Locate browser.cache.disk.capacity in the list of results and double-click it.
    • Change the value to 50000 or any other value.
    • Be sure to use the value that is lower than the default value.

After making the changes restart Firefox and check if the problem is resolved. Keep in mind that changing this value can reduce your performance and make Firefox slower.

If Firefox becomes too slow, be sure to use a higher value or revert it to default.

According to users, you can fix this problem by changing the browser.cache.disk.capacity option. By changing this option, you can limit the amount of memory that Firefox uses.

By doing so, you’ll reduce performance but you’ll also cap the amount of memory Firefox uses.


16. Use Firemin

If you’re having issues with memory usage on Firefox, you might be able to solve that issue by using Firemin.

This tool allows Firefox to release unused memory periodically and drastically reduce memory usage as a result.

The tool is free and simple to use and if Firefox uses too much memory, be sure to download Firemin. There’s also a portable version available so you don’t have to install the application in order to run it.


High memory usage on Firefox will affect your PC performance, but you should be able to fix it by using one of our solutions listed above.

If any of them worked for you, be sure to tell us in the comments section below. Also, if you have any more questions, don’t hesitate to drop them there, too.

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What a nice thorough list in one place. I’m looking forward to trying these. I’ve been able to keep 100s of tabs open (not loaded, only open) on a Vista machine with 2G. I’m now on Win 10 and it’s out of memory with 20 tabs. Something needs changes…. 🙂

Very thorough writeup.
I have no addons, no extensions, no flash, tried safe mode, etc… and firefox is still demanding half a gig of ram. So here´s something you forgot to put on the list…

Instead of spending 2 hours doing all the above, simply close firefox and open Internet Explorer
Problem Solved in 2 seconds instead of 2 hours.

“ComputerClass Day1: this is a computer…
ComputerClass Day2: IE is rubbish use FF, MS is rubbish, use Linux
ComputerExpert Year7: Stay with Win7 – it works !!!”