Couldn’t load XPCOM on Firefox in Windows 10

Milan Stanojevic
by Milan Stanojevic
Deputy Editor
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  • Users have reported issues when trying to load XPCOM on Mozilla Firefox.
  • The article below will show you exactly what needs to be done if that happens to you too.
  • To learn more about Mozilla Firefox, check out our dedicated Firefox page.
  • We also have a dedicated Browsers page filled with info on all major web browsers.
Couldn’t load XPCOM firefox

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.

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%. Press Enter or click OK.
  2. Temp folder will now open. Select all files from the Temp folder and delete them.

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.

Fix – Couldn’t load XPCOM on Tor

Add Tor folder to the exclusions list

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.

Editor’s Note: This post was originally published in December 2019 and has been since revamped and updated in August 2020 for freshness, accuracy, and comprehensiveness.

Editor's Note: This article was originally published in September 2016 and was revamped and updated in August 2020 for freshness, accuracy, and comprehensiveness.