What will happen if my Personal Profile for Mozilla Firefox is deleted on my Mac computer?

If your Personal Profile for Mozilla Firefox was deleted by accident, you will lose browsing history and all custom settings. And you will not be able to start Firefox.

If you don't care about browsing history and custom settings, you can try the following:

1. Close Firefox and remove it from Dock:

2. Delete the profile:

$ cd /Users/{user}/Library/Application\ Support/Firefox/Profiles
$ rm -R *

$ cd /Users/{user}/Library/Caches/Firefox/Profiles
$ rm -R *

3. Start Firefox again. You will see an error message:

Profile Missing 

Your Firefox profile cannot be loaded. It may be missing or inaccessible.

4. In order to recover from this error, you can delete the profiles.ini file or the Firefox folder:

$ rm /Users/{user}/Library/Application\ Support/Firefox/profiles.ini

$ rm -iR /Users/{user}/Library/Application\ Support/Firefox/* 

5. Start Firefox again. It will guide you to create a new profile.

⇒ Uninstall Mozilla Firefox from Mac Computer

⇐ Mozilla Firefox Personal Profiles on Mac

⇑ Using Mozilla Firefox on Mac Computer

⇑⇑ Firefox - Frequently Asked Questions