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Fix: High CPU Usage with the Firefox browser on the Computer

Are you experiencing high CPU usage in Mozilla Firefox? Learn different troubleshooting methods to optimize browser performance.

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 avoiding using many third-party add-ons running in the background.

You can also clear the cache and adjust the Firewall settings to reduce CPU usage.

Fix: High CPU Usage on Firefox browser

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

Whether on the customization front or efficient tab management, there’s much to look forward to. Moreover, it doesn’t hog too many system resources compared to its Chrome counterpart.

Firefox Browser High CPU usage in Windows Task Manager

I recently switched to Firefox and noticed my PC’s performance was constantly declining. Upon investigating it further via Windows Task Manager, the Firefox browser was the primary culprit. It was exhausting more than expected 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, this guide shall help you.

Try out the Basic Fixes

Before moving on to the slightly advanced fixes, let’s start with some fundamental ones known to rectify the underlying issue more often. 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 recommended to be on the latest browser build. If that is not the case, then consider updating it right away. Click on the Menu horizontal 3bar icon and select Download Firefox Update.
    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.

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

Boot Firefox to Safe Mode

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

Here are the steps to boot Firefox in Safe Mode:

  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 Safe Mode.

Check how it is performing now. If you notice considerable improvement, 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 add more browser features, they could cause a few issues. In those cases, removing them and looking for alternatives is best.

Use Strict Tracking Protection

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

Here are the steps to enable Strict privacy:

  1. Launch the Firefox app on a computer.
  2. Click on the Menu horizontal 3bar icon and select the Options menu.
  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 most significant drawbacks of the Strict Mode is that its heavy protection mechanism could break some websites and their contents. So you might have to brace yourself for this tradeoff.

Enable Hardware Acceleration

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

Here are the steps to enable hardware acceleration:

  1. Launch the Firefox browser on a computer.
  2. Click on the Menu horizontal 3bar icon and select the Options menu.
  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 checkbox.

See if it manages to fix the high CPU usage issue of Firefox. The hardware acceleration feature depends 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 (8). This makes it easier for the browser to deal with multiple opened tabs simultaneously. 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:

  1. Launch Mozilla Firefox 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 check whether the high CPU usage issue has been settled. 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 data gets corrupted, it could harm the browser’s overall performance. So it is recommended to delete this file and let Firefox automatically create its new instance.

  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. 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 abovementioned methods gave favorable results, resetting the browser’s default state is time.

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

Here are the steps to complete reset the Firefox browser:

  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 is 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 will lose all the installed extensions and configurations you made to the browser. However, if it ends up fixing the issue, then it’s worth the effort. I just checked if this has fixed the high CPU usage.

Bottom Line

So this was all from this guide; you could fix the high CPU usage issue with the Firefox browser. We have shared seven fixes that could help you rectify high CPU usage in the Firefox browser.

Installing some third-party extensions kept the browser’s processes up and running all the time, leading to high resource consumption. So on booting the browser to Safe Mode, I could identify that the culprit was these add-ons.

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

If none of the above fixes work for you, then switching to an alternative browser for your computer is better. We have already listed the best browser for Windows and macOS.

That said, let us know which spelled out success in your case. Also, please share if anything else has helped you fix the issues.

Lastly, if you've any thoughts or feedback, then feel free to drop in below comment box. You can also report the outdated information.

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Kushal Azza

Kushal Azza

Kushal Azza is a Google Certified IT Professional, Digital Content Creator, and Go-To Digital Marketer with Engineering Degree. He has over a decade of experience solving tech problems, troubleshooting, and innovating digital solutions. Follow him on Twitter and LinkedIn.

2 comments and feedback

  1. I was trying to diagnose issues with Windows and a laptop that had freezing issues. So I installed Ubuntu 22.04LTS. When running Firefox or Edge browser I experienced strange spikes with CPU. Although the spikes would affect one core at a time or move from a virtual core to a logical core. At first I thought maybe it was due to fractional scaling, so I went back to 100% scale. Still saw random 100% spikes with cores and fan would max out. Temps would go from 40c to 80c in an instant. I tried re-applying thermal paste which reduced idle temps from 40c to 35c so I knew it was effective. Mind you this is only a 10th gen. Core i3 10110u dual core CPU. After awhile I noticed the spikes also was causing the laptop to freeze up as well. Telling me, there was some serious heat issues.

    1. Hi John, is your system running on the SSD or HDD? Generally, the mechanical HDD has a major effect on the system’s performance, causing the over usage of CPU for minimal activity. SSD makes the overall system smooth and irons out all the CPU-related issues.

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