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.

Updating Firefox to the latest version

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

Add-ons

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.

• For more information on starting Firefox in Safe Mode and on how to find which extension or theme is causing your problem, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

Hiding intrusive content

Many web pages have content you don't really need that uses memory to display. If Adobe's Flash Player plugin is installed, use the "Ask to Activate" setting in the Add-ons Manager Plugins panel to prevent automatic loading of unwanted Flash content, See the Set Adobe Flash to "click to play" on Firefox article for details.

Some extensions allow you to block such unnecessary content; for example:

• uBlock Origin allows you to hide ads on websites.
• NoScript allows you to selectively enable and disable all scripts running on websites.

Checking Flash hardware acceleration

If Adobe's Flash Player plugin is installed, rendering of Flash video content 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.

• Check that hardware acceleration is turned on and that your graphics drivers are up-to-date.

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:

• Bookmarks. Hint: "Bookmark All Tabs" will bookmark a set of tabs.
• To-do list applications.

Other applications using up memory

Having many applications running simultaneously may cause your computer to run slowly and other applications to do so 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
  • Even if you're not a C++ programmer, you can try your hand at some other tools and tips Firefox developers use to debug leaks.

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)