How to Fix: High CPU Usage with Firefox browser?

High CPU usage in the Firefox browser is mainly due to the parsing of heavy website elements and background processes. It can be fixed by tweaking browser configuration and avoid using a large number of third-party add-ons running in the background.

Firefox is often regarded as the epitome of a secure browsing experience. Likewise, it also boasts a plethora of useful feature sets, which more often than not, checkmarks all the important prerequisites for the end-user.

Whether it is on the customization front or efficient tab management, there’s a lot to look forward to. Moreover, it doesn’t hog too many system resources as compared with its Chrome counterpart. Or so I thought.

Firefox Browser High CPU usage in Windows Task Manager

Upon recently switching to Firefox, I noticed my PC’s performance was constantly on the decline. Upon investigating it further via Windows Task Manager, the Firefox browser turned out to be the major culprit. It was exhausting more than the expected level of RAM and other related resources.

Moreover, it wasn’t a one-off case either. Many concerned users have posted the same query across various Mozilla Support Forums. If you are also on the same page and facing high CPU usage issues with the Firefox browser, then this guide shall help you out.

Try out the Basic Fixes

Before moving on to the slightly advanced fixes, let’s start off with some fundamental ones that are known to rectify the underlying issue more often than not. In this regard:

  • The first fix calls for quitting and then restarting Firefox. Make sure to save all the opened tabs before doing so.
  • Next up, it is also recommended to be on the latest build of the browser. If that is not the case, then consider updating it right away. Click on the Menu horizontal 3bar icon and select Download Firefox Update. You may also manually download and install it onto your PC.
    Download Firefox Update Notification
  • Likewise, it is also recommended that you properly shut down your PC (no sleep or hibernation) and then restart it. Once it boots up, launch the browser and see if the high CPU usage has been fixed or not.

These were the most basic fixes that often resolve the temporary CPU fluctuation. If this doesn’t help, you can follow along with the advanced troubleshooter.

Boot Firefox to Safe Mode

When you boot the browser to Safe mode, it will disable all the third-party add-ons, themes, and extensions. So if the browser performs along the expected lines in this mode, then the extensive resource consumption could well be attributed to any of these add-ons. Hence you should consider disabling it.

Here are the steps to boot Firefox in Safe Mode with disabled add-ons:

  1. Launch the Mozilla Firefox browser
  2. Click on the Menu horizontal 3bar icon situated at the top right.
  3. Select Help > Restart With Add-ons Disabled from the drop-down.
    Firefox Restart with Add-ons Disabled
  4. This will launch the browser in the Safe Mode.

Check how it is performing now. If you notice considerable improvement, then boot the browser back to normal mode and uninstall the recently installed extensions, one at a time, until the performance issue is rectified.

While third-party add-ons do add more features to the browser, they could well be the cause of a few issues. In those cases, it is best to remove them and look for their alternatives.

Use Strict Tracking Protection

Firefox comes with three different levels of tracking protection: Standard, Strict, and Custom. It is the Strict one that is known to block most of the trackers, cookies, and contents across various sites. This in turn might speed up the loading time of various sites as well. So you could consider enabling it.

Here are the steps to enable Strict privacy in the Firefox browser:

  1. Launch the Firefox browser on a computer.
  2. Click on the Menu horizontal 3bar icon and select Options.
  3. Switch to the Privacy and Security section from the left menu bar.
  4. Select the Strict mode from the Enhanced Tracking Protection section.
    Enable Strict Privacy for Firefox Computer Browser
  5. Now check and see if it gives out any favorable results.

One of the biggest drawbacks of the Strict Mode is that its heavy protection mechanism could break some of the websites and their contents. So you might have to brace yourself for this tradeoff.

Enable Hardware Acceleration

When dealing with graphics-intensive components, Firefox uses your PC’s main process by default. However, other apps will then might not be able to make optimal usage of the RAM and hence could slow down the entire PC. Therefore, consider instructing the browser to make use of the PC’s graphics processor rather than the main one.

Here are the steps to enable the hardware acceleration in Firefox:

  1. Launch the Firefox browser on a computer.
  2. Click on the Menu horizontal 3bar icon and select Options.
  3. Scroll to the Performance section under the General tab.
  4. Uncheck the Use recommended performance settings option.
    Use Hardware Acceleration when available in Firefox
  5. Enable the Use hardware acceleration when available option.

See if it manages to fix the high CPU usage issue of Firefox. The hardware acceleration feature is totally dependent on the graphics processor, hence a weaker chipset might not give out a preferable mileage.

Decrease Content Process Limit

By default, Firefox allocates the maximum available content process (which is 8). This makes it easier for the browser to deal with multiple opened tabs at once. But on the flip side, it also leads to more RAM consumption. Hence you could consider decreasing its value for optimum RAM usage.

Here are the steps to reduce the content process limit in firefox:

  1. Launch the Firefox browser on a computer.
  2. Click on the Menu horizontal 3bar icon and select Options.
  3. Scroll to the Performance section under the General tab.
  4. Uncheck the Use recommended performance settings option.
    This shall bring up the Content process limit drop-down menu.
  5. Change the value from 8 to something lower, say 4.
    Setting Content Process Limit in Firefox Computer

Restart Firefox and then check if the high CPU usage issue has been settled or not. Decreasing the content process limit might give you a hard time dealing with multiple tabs simultaneously. So consider keeping the number of opened tabs to a lower level.

Delete content-prefs.sqlite file

The content-prefs.sqlite file beholds data related to the user profiles. But if any bit of data gets corrupted, it could have a negative impact on the overall performance of the browser. So it is recommended to delete this file and let Firefox automatically create its new instance.

Here are the steps to delete firefox profile with content-prefs.sqlite:

  1. Launch the Mozilla Firefox browser
  2. Click on the Menu horizontal 3bar icon situated at the top right.
  3. Select Help > Troubleshooting Information option.
    Firefox Help Troubleshooting Information tab
  4. Within the Application Basics section, go to Profile Folder and click on the Open Folder button.
    Open Profile Folder for Firefox Browser
  5. Select the content-prefs.sqlite file and Delete it.
    content-prefs.sqlite file in Firefox computer profile folder

Once done, restart the browser and see if the resource consumption has been minimized or not. Upon deleting the above file, you might notice some settings not synced with your preferences. So make sure to set it accordingly.

Refresh Firefox (Reset)

If none of the aforementioned methods managed to give out favorable results, then it’s time to reset the browser back to its default state.

Note: Firefox Reset will remove all the third-party add-ons and customizations that you had made to the browser. However, your data (bookmarks, password, etc.) will stay safe.

Here are the steps to reset and refresh firefox browser on computer:

  1. Copy-paste about:support in the Firefox address bar, and hit Enter key.
    This shall take you to the Troubleshoot page.
  2. Click on the Refresh Firefox… button situated at the right.
    Reset and Refresh Firefox BrowserThis will open a dialog box for confirmation.
  3. Hit on the Refresh Firefox command button.
    Refresh Firefox command button
  4. Wait for the process to complete and relaunch the Firefox browser.

Upon carrying out these steps you would lose all the installed extensions as well as any configurations you made to the browser. However, if it ends up fixing the issue, then it’s worth the efforts. Just checked if this has fixed the high CPU usage.

Bottom Line: Firefox High CPU Usage

So this was all from this guide on you could fix the high CPU usage issue with the Firefox browser. We have shared a total of seven different fixes that could help you in rectifying high CPU usage in the Firefox browser.

In my case, the installing of some third-party extensions was keeping the browser’s processes up and running all the time, which in turn lead to high resource consumption. So on booting the browser to Safe Mode, I was able to identify that the culprit was indeed these add-ons.

Hence upon removing the recently installed extensions, the CPU usage was back along the expected lines.

If none of the above fix work for you, then it’s better to switch to an alternative browser for your computer. We have already listed the best browser on Windows and macOS.

With that said, do let us know in the comments section which one spelled out success in your case.

Lastly, here are the recommended web browsers for your computer and mobile phone that you should give a try.

WindowsMacOSiOSAndroidLinux
Chrome WindowsChrome MacChrome iOSChrome AndroidFirefox Linux
Firefox WindowsSafari MacSafari iOSEdge AndroidChrome Linux
Edge WindowsFirefox MacEdge iOSSamsung InternetEdge Linux

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