We're calling on all EU-based Mozillians with iOS or iPadOS devices to help us monitor Apple’s new browser choice screens. Join the effort to hold Big Tech to account!

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 go to start Firefox on a new Macbook Pro, I get a message saying it can't open because another copy of Firefox is already running -- how can I get Firefox to start?

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

more options

We have a new Macbook Pro running OSX 10.6.5. I downloaded and installed Firefox 3.6.12.dmg. After having used Migration Assistant to bring files, folders and other [but not applications] over from an older Macbook Pro and thus creating a second user, whenever I go to start Firefox, a box pops up saying that there is already a copy of Firefox running, and that only 1 instance can run at a time. I cannot locate this "second copy".

We have a new Macbook Pro running OSX 10.6.5. I downloaded and installed Firefox 3.6.12.dmg. After having used Migration Assistant to bring files, folders and other [but not applications] over from an older Macbook Pro and thus creating a second user, whenever I go to start Firefox, a box pops up saying that there is already a copy of Firefox running, and that only 1 instance can run at a time. I cannot locate this "second copy".

All Replies (2)

more options

OK -- I found the solution -- see http://kb.mozillazine.org/Profile_in_use In my case, there was no ".parentlock" file, but using ProfileManager to create a new profile seems to have resolved the issue.

more options