Firefox uses too many CPU resources - How to fix

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  • Revision id: 20208
  • Created:
  • Creator: NHDaly
  • Comment: Added NoScript to list of AddOns that Hide Bothering Content.
  • Reviewed: Yes
  • Reviewed:
  • Reviewed by: Verdi
  • Is approved? Yes
  • Is current revision? No
  • Ready for localization: Yes
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  • Readied for localization by: Verdi
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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.

Updating to the latest version

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

Extensions and themes

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 Troubleshoot Firefox issues using 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 bothering content

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

  • Adblock Plus allows you to hide 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 CPU, 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 CPU consuming plugins

You can test to see whether one of your plugins is causing Firefox to use too much CPU 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 CPU 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 CPU usage after disabling a certain plugin, you may leave it disabled. If 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 CPU usage.

  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.

Check hardware acceleration is turned on and your graphic drivers are up-to-date.

Submitting performance data to Mozilla

If you check Submit performance data, Mozilla will gather data including CPU usage for your Firefox, which will help making Firefox better for future versions.

Based on information from Firefox CPU usage (mozillaZine KB)