Couldn’t load XPCOM: 9 Ways to Fix it in Firefox, Tor & Windows

Failed updates are the main cause of this problem

by Milan Stanojevic
Milan Stanojevic
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... read more
Fact checked by Alex Serban
Alex Serban
Alex Serban
Browser & Networking Expert
After moving away from the corporate work-style, Alex has found rewards in a lifestyle of constant analysis, team coordination and pestering his colleagues. Holding an MCSA Windows Server... read more
Affiliate Disclosure
  • The Couldn't load XPCOM error message appears mostly because of a failed Firefox update.
  • If you are dealing with this issue, the fastest solution is to switch to another browser.
  • Creating a new profile can solve the Firefox error Couldn't load XPCOM in Windows.
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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.

What does Cannot load XPCOM mean?

What is an XPCOM file?

XPCOM is short for Cross Platform Component Object Model and it is a cross-platform component model from Mozilla.

Without it, Firefox cannot function properly and it might be frustrating because you can’t use it to its full extent.

What are the common causes for the Cannot load XPCOM error?

The Cannot load XPCOM appears because this component is missing. This usually happens because of a failed Firefox update.

If the update didn’t install properly, you now have mixed old and new files within the Firefox folder.

Another common cause for this issue is that your third-party security software has blocked some of the Firefox components for security reasons.

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 messages
  • Xulrunner couldn’t load XPCOM – the error that can also appear on Mac
  • Couldn’t load XPCOM Firefox portable – it is the same as on the full version

So, after clearing these things, let’s see how we can fix the Couldn’t load XPCOM error.

How do I fix Couldn’t load XPCOM?

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 fast and also has a high level of customization at no cost at all.

2. Completely remove Firefox and reinstall it

  1. Click the Start button and select Settings.
  2. Choose Apps.
  3. Now look for Mozilla Firefox within the list of apps, click on it and select Uninstall.
  4. Follow the instructions on the screen to complete the process.

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

You need to uninstall the Firefox application from your PC, as shown above, but that might prove to be insufficient.

To fix this problem you’ll have to completely remove all files associated with Firefox. To do that, press the Windows key + E to start File Explorer, then remove these folders (for 32-bit and 64-bit versions):

C:\ProgramFiles\Mozilla Firefox
C:\ProgramFiles(x86)\Mozilla Firefox

Some of our readers also suggested removing the following folders from your PC:

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

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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, then press Enter or click OK.
  2. Click the Create Profile button.
  3. Click Next.
  4. Enter the name of your new profile and click Finish.
  5. If you want, you can also set the storage directory for this profile.
  6. 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 of our readers also suggested removing your Firefox profile completely and then creating a new one, so you might want to try that as well.

4. Delete everything from the 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 icon
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 in Firefox

This is a native problem for Firefox since XPCOM is a component of the browser created by Mozilla.

By using the solutions above, you should be able to make the browser work again. If not, there is also the option of using another browser, like we recommended in Solution 1 of this guide.

6. Couldn’t load XPCOM in Windows 10/11

This is not a Windows 10 or 11 problem because it is caused by a problematic update of Firefox.

Therefore, all solutions will help you fix the browser whether you’re using it on any PC, including on Windows 10 & 11.

7. Couldn’t load XPCOM in Windows 7

As we’ve highlighted above, Couldn’t load XPCOM doesn’t have anything to do with the OS you’re using although we strongly recommend updating to a newer OS.

Completely removing Firefox by uninstalling it and removing its folders, then reinstalling it, should fix the problem even if you’re using Firefox on Windows 7.

8. Couldn’t load XPCOM in Thunderbird

Thunderbird is a browser that is also made by Mozilla and it has the same XPCOM component that may fail after an incomplete update.

As for its most famous brother, to fix this problem, Mozilla recommends a clean reinstallation of Thunderbird.

That includes uninstalling the program, deleting its folder from C:\Program Files\Mozilla Thunderbird\ or C:\Program Files (x86)\Mozilla Thunderbird\, and reinstalling a fresh copy of Thunderbird.

9. 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 the 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.

You may also find it useful to read our guide on how to fix Firefox when it’s not responding in Windows 10/11.

For any other suggestions or questions, feel free to use our comments section below.

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