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

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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 such as ads and that uses memory to display (see the plugin section below). Some extensions allow you to block such unnecessary content:

  • Adblock Plus lets you block ads on websites.
  • 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 press Disable 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

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

If you're a C++ programmer, you can even try your hand at some of the tools Firefox developers use to debug leaks.

  • 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.

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