Firefox uses too many CPU resources - How to fix

At times, Firefox may require significant CPU resources in order to download, process, and display web content. If you are experiencing periods of sustained high CPU usage while using Firefox, this article presents some options for you to review.

  • The CPU (Central Processing Unit) is the "brain" of the computer. When the CPU is being heavily used, the overall performance of the computer can be impacted.
  • Depending on your operating system, you can review and monitor CPU usage through specific tools. On Windows, the Performance tab of the Windows Task Manager displays the rate of CPU consumption.
Note: If you send performance data, Mozilla will gather data including the CPU usage for your Firefox, which will help making Firefox better for future versions.

Updating to the latest version

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


Disabling CPU consuming extensions and themes

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

To determine if an extension or theme is causing Firefox to use too much CPU, start Firefox in its Safe Mode and observing its CPU 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 need, such as ads, but which still use CPU resources to display its content. Firefox's built-in Content blocking can help save CPU resources by preventing third-party tracking content from loading. See the Content blocking article for details.

Some extensions allow you to block unneeded content; for example:

Checking Flash hardware acceleration

If Adobe's Flash Player plugin is installed, video content rendering in full screen can be accelerated by hardware. It eases CPU usage in case of a dedicated graphics card.

  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 CPU usage.

Corrupt content-prefs.sqlite file

Firefox stores your data in various files in your profile folder. The file used for saving individual website settings might be corrupt. If you delete that file, your zoom level settings will be reset, but it should decrease CPU usage.

  1. Click the menu button Fx57menu , click Help and select Troubleshooting Information.From the Help menu, choose Troubleshooting Information. The Troubleshooting Information tab will open.

    • Under the Application Basics section, click on Open FolderShow in FinderOpen Directory. A window will open that contains your profile folder.Your profile folder will open.
    Note: If you are unable to open or use Firefox, follow the instructions in Finding your profile without opening Firefox.
  2. Click the menu button New Fx Menu and then click ExitQuit Close 29 .

    Click the Firefox menu Fx57Menu , then click Exit. Click the Firefox menu at the top of the screen, then click Quit Firefox.Click the Firefox menu Fx57Menu , then click Quit.

  3. In your profile folder, delete the file content-prefs.sqlite. It will be recreated next time you open Firefox.

Based on information from Firefox CPU usage (mozillaZine KB)

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