Join the AMA (Ask Me Anything) with the Firefox leadership team to celebrate Firefox 20th anniversary and discuss Firefox’s future on Mozilla Connect. Mark your calendar on Thursday, November 14, 18:00 - 20:00 UTC!

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

Firefox won't start, but possible to troubleshoot as compatibility. how can I fix this without running compatibility?

  • 2 replies
  • 3 have this problem
  • 1 view
  • Last reply by FredMcD

more options

2014 April 29, Firefox works fine but April 30 it won't start, the possible to work is running compatibility (troubleshoot). Is there any solution for this without running compatibility or without formatting computer? And works during 2014 April 29.

I've already uninstall anti virus I try also restore and repair windows I've also uninstall and reinstall firefox. still doesn't work :(

2014 April 29, Firefox works fine but April 30 it won't start, the possible to work is running compatibility (troubleshoot). Is there any solution for this without running compatibility or without formatting computer? And works during 2014 April 29. I've already uninstall anti virus I try also restore and repair windows I've also uninstall and reinstall firefox. still doesn't work :(

All Replies (2)

more options

If you can start Firefox in troubleshooting mode but not in normal mode, it's quite likely that your problems are caused by a misbehaving addon. Try starting in troubleshooting mode, going to the addons manager and disabling all addons. Then restart in normal mode.

If that makes the issue go away, you can try re-enabling your addons one after another, restarting after each one, until you have the issue again. The you know that that addon is misbehaving and can remove it permanently.


hope that helps, till

more options

If you had an update of Firefox, the firewall may be the problem.

This problem occurs when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again:

  • Make sure your Internet security software is up-to-date (i.e. you are running the latest version)

  • Remove Firefox from your program's list of trusted or recognized programs, then add it back. For detailed instructions, see Configure firewalls so that Firefox can access the Internet.