Join the Mozilla’s Test Days event from Dec 2–8 to test the new Firefox address bar on Firefox Beta 134 and get a chance to win Mozilla swag vouchers! 🎁

This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

When I try to open Firefox, I get "couldn't load XPCOM" What does it mean? What do I do?

  • 2 replies
  • 11 have this problem
  • 2 views
  • Last reply by cor-el

more options

I was unable to open Firefox, so did a system restore. Now, when I try to open Firefox, I get "couldn't load XPCOM" Where do I find a solution?

I was unable to open Firefox, so did a system restore. Now, when I try to open Firefox, I get "couldn't load XPCOM" Where do I find a solution?

All Replies (2)

more options
more options

This usually happens because of a failed Firefox update that left you with a mixture of old and updated files in the Firefox program folder. This can happen in case security software was keeping a handle of some of the files in the Firefox program folder preventing Firefox from replacing all the files.

Do a clean reinstall and delete the Firefox program folder before (re)installing a fresh copy of the current Firefox release.

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

  • Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

  • (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
  • (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you uninstall and (re)install or update Firefox, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.