Couldn’t load XPCOM on Firefox in Windows 10/11

Milan Stanojevic
by Milan Stanojevic
Windows & Software Expert
Milan has been enthusiastic about PCs ever since his childhood days, and this led him to take interest in all PC-related technologies. Before joining WindowsReport, he worked as a front-end web developer. Read more
Affiliate Disclosure
  • The Couldn't load XPCOM error message appears mostly because of a failed Firefox update.
  • If you are dealing with XPCOM error, the fastest solution is to switch to another browser.
  • Creating a new profile can solve the Firefox error Couldn't load XPCOM in Windows 10.
  • If you're using Tor and see the Couldn't load XPCOM error, check the antivirus settings.
Couldn’t load XPCOM firefox
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Problems with Firefox, or other applications, will occur sooner or later, therefore it’s important to know how to fix those problems.

Users reported Couldn’t load XPCOM error message on Windows 10, while trying to start certain applications, so let’s see if we can fix this problem.

The solutions listed below will also prove useful if you are encountering the following issues:

  • Couldn’t load XPCOM-an error about XPCOM missing
  • Firefox couldn’t load XPCOM – it appears because of a failed update
  • Couldn’t load XPCOM Windows 10 – it is similar to the first error message
  • Firefox couldn’t load XPCOM Windows 10 – similar to the other Firefox related message

How do I fix XPCOM loading errors?

1. Consider using another browser

If Firefox is giving you a hard time in general, and not just because of the XPCOM issues, then maybe you should consider using a different browser entirely.

On that note, we recommend you give Opera a shot. This web browser is built using the Chromium engine, just like Edge and Chrome, and it is extremely stable and reliable, allowing for near-zero errors to occur.

It also has some extra tools that most other browsers don’t except through the use of extensions, such as a built-in VPN, and a very efficient ad-blocker.



Enjoy an error-free browser that is incredibly fast and also has a high level of customization at no cost at all.

2. Completely remove Firefox and reinstall it

Users reported that this error occurs when they try to open Firefox and that they are unable to use Firefox at all.

This can be a major problem if you use Firefox as your default web browser, but you should be able to fix this problem simply by reinstalling Firefox.

To do that, first you need to uninstall Firefox application from your PC. Uninstalling Firefox isn’t usually enough, and to fix this problem you’ll have to completely remove all files associated with Firefox.

To do that, remove these folders:

  • C:\Program Files\Mozilla Firefox
    • If you’re using a 32-bit version of Windows 10
  • C:\Program Files(x86)\Mozilla Firefox
    • If you’re using 64-bit version of Windows.

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Users are also suggesting to remove the following folders from your PC:

  • C:\Users\your_user_name\AppData\Local\MozillaFirefox
  • C:\Users\your_user_name\AppData\Local\Mozillaupdates
  • C:\Users\your_user_name\AppData\Local\VirtualStore\Program Files\Mozilla Firefox

After uninstalling Firefox and removing its installation directory, download the latest version of Firefox and install it. When the installation process is finished, start Firefox and check if the problem is resolved.

3. Create a new Firefox profile

  1. Press Windows Key + R and enter firefox.exe -p.
  2. Press Enter or click OK.
  3. Click the Create Profile button.
  4. Click Next.
  5. Enter the name of your new profile and click Finish.
  6. If you want, you can also set the storage directory for this profile.
  7. Select the profile that you just created and click Start Firefox button.

Note: After creating a new profile you just need to check if this problem is resolved. If everything works without a problem, just keep using your new Firefox profile and everything should be in order.

Some users are also suggesting to remove your Firefox profile completely and then create a new one, so you might want to try that as well.

4. Delete everything from Temp folder and disable your antivirus program

  1. Press Windows Key + R and enter %temp%.
  2. Press Enter or click OK.
  3. Temp folder will now open.
  4. Select all files from the Temp folder and delete them.

Note: If deleting files from the Temp folder doesn’t solve the issue, we suggest that you try disabling your antivirus software.

Antivirus can sometimes interfere with certain applications and cause this and many other errors to appear, therefore be sure to disable it and check if that solves the problem.

If disabling the antivirus doesn’t fix the problem, you might want to temporarily remove it and check if that solves this error.

5. Couldn’t load XPCOM on Tor

According to users, this error appears if you’re using Tor along with Malwarebytes, and in order to fix this problem, you need to add entire Tor installation directory to the list of exclusions in Malwarebytes.

After doing that, you need to disable Malwarebytes and reinstall Tor completely.

Couldn’t load XPCOM error usually appears while starting Firefox, but in most cases, this problem can be fixed simply by reinstalling Firefox. If that doesn’t work, feel free to try any other solution from this article.

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