How to Fix: High CPU Usage with 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. Or so I thought.

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

Related: Mozilla Firefox vs. Google Chrome: Which is better?

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 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 recommended to be on the latest browser build. If that is not the case, then consider updating it right away. Click on the Menu  and select Download Firefox Update. You may also manually download and install it onto your PC.
  
• 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

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 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 with disabled add-ons:

1. Launch the Mozilla Firefox browser
2. Click on the Menu  situated at the top right.
3. Select Help > Restart With Add-ons Disabled from the drop-down.
   
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 features to the browser, they could well 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 in the Firefox browser:

1. Launch the Firefox browser on a computer.
2. Click on the Menu  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.
   
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 usage of the RAM and hence 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 in Firefox computer:

1. Launch the Firefox browser on a computer.
2. Click on the Menu  and select Options.
3. Scroll to the Performance section under the General tab.
4. Uncheck the Use recommended performance settings option.
   
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 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 (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  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.
   

Restart Firefox and then 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 bit of 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.

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

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

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, it’s time to reset the browser’s default state.

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 reset and refresh the Firefox browser on your 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 is situated at the right.
   This will open a dialog box for confirmation.
3. Hit on the 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: Firefox’s High CPU Usage

So this was all from this guide; you could fix the high CPU usage issue with the Firefox browser. We have shared seven different 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.

Related: How to Fix: Mozilla Firefox not Loading Pages?

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