Tap here to go to the mobile version of the site.
Your Firefox is out of date and may contain a security risk! Upgrade Firefox

Support Forum

error message I'm getting is "Couldn't load XPCOM", when i try to start FF from the Desktop icon


error mssg = "Couldn't load XPCOM" when I click the icon on my desktop to start FF. I don't know what XPCOM is or how to fix it.

Additional System Details


  • User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; BTRS100194; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET4.0C)

More Information

  • Top 25 Contributor
529 solutions 5045 answers

Helpful Reply


Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove Firefox program files (not bookmarks, history, passwords, etc unless you check to do so) and then reinstall Firefox. Please follow these steps:

Note: You might want to print these steps or view them in another browser.

  1. Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer.
  2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
  3. Delete the Firefox installation folder, which is located in one of these locations, by default:
    • Windows:
      • C:\Program Files\Mozilla Firefox
      • C:\Program Files (x86)\Mozilla Firefox
    • Mac: Delete Firefox from the Applications folder.
    • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
  4. Now, go ahead and reinstall Firefox:
    1. Double-click the downloaded installation file and go through the steps of the installation wizard.
    2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

Please report back to see if this helped you!

Thank you.

finkelskoehn 0 solutions 1 answers

Danke für die Hilfe!!!! Es hat bei mir sogar schon ausgereicht, lediglich Firefox neu zu installieren. War mir anfangs natürlich nicht gelungen, weil immer wieder nur die Fehlermeldung "Couldn`t load XPCOM`auftrat. Daher habe ich den Internet Explorer aufgemacht und dann den Firefox neu installiert. Jetzt funktioniert wieder alles wie es soll!

Kadir Topal
  • Administrator
  • Moderator
22 solutions 175 answers

Hi Caroljean, did any of the suggestions in this thread solve your problem?

Philocalist 0 solutions 3 answers

Helpful Reply

Just in case someone else stumbles across this: I experienced the same problem - no real idea of the cause, though it appeared after an unexplained BSOD on a Vista machine (which in turn happened after I had to clone then swap out my existing C drive - all had been running for a few days after the drive swap - I'm usually 'on' 24/7, but this time period had included several voluntary reboots, so all appeared to be functioning OK after the swap, before the BSOD.

Anyway, after reading many threads similar to this one, my own fix was stupidly simple and has proven to be 100% effective: I simply went to Mozilla and downloaded the current version of Firefox - I then just let it do its own thing and 'upgrade' my current installation, and a few minutes later, Firefox is up and running with all of my setings, add-ins etc fully intact and operational!

Modified by Philocalist

elexier909 0 solutions 1 answers

Both me and my wife are getting this too, Makes using Nightly COMPLETELY un-usable. Stranded firefox works fine as does internet explorer (I scrubbed thoroughly afterwards :P )

I have COMPLEATLY removed firefox and nightly and restarted and don a freash install and still getting the same error on nightly.

Guess the recent build went bad:(

mimimimo 0 solutions 2 answers

I used nightly too and got this error message too (actually, I got two pop-ups: one about a missing dll and the other about XPCOM). I didn't uninstall anything. I just download the fresh copy of express installer of Nightly from their website, run it and that's it. All my bookmarks, extensions, and add-ons are still there.

  • Top 10 Contributor
  • Moderator
10749 solutions 96724 answers

You can try to reboot the computer after having deleted the Firefox program folder.

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) if installing Firefox Nightly still isn't working properly.

InaSaba 0 solutions 1 answers

Could not even download Fire Fox. Tried different steps listed in this forum. Nothing worked, Uninstalling, Cleaning Registry with CC Cleaner, tried downloading etc . Finally after more than three hours of performing various steps, I gave up and installed Google Chrome. I was not very happy with it and decided to download Fire Fox one more time with Chrome. It worked like charm. I am back in business.

Thanks Mozilla.

RadicalDudette 2 solutions 13 answers

I would rather have FF 24. It is in my programs so what is the problem.

RadicalDudette 2 solutions 13 answers

I would have to use FF 27 and I do not wish to have that. How can I get back FF 24? I may just go to Google Chrome.

  • Top 10 Contributor
  • Moderator
10749 solutions 96724 answers

Did you try to delete the Firefox program folder where the Nightly is installed and possibly use the ZIP version instead?