Profile in use

From MozillaZine Knowledge Base

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Firefox , Thunderbird , Mozilla Suite and SeaMonkey are designed to allow only one copy of a Mozilla application to access a profile at the same time, to avoid conflicts. It does this by checking for the existence of a lock file when it starts. If the lock file already exists it exits with an error message. Otherwise it creates a lock file in the profile and deletes it when exits. Normally this is completely transparent to the user. However, if the Mozilla application exits abnormally it might not delete the lock file, preventing you from using that profile.

This article will help you regain access to a locked profile.


Indications that your profile is locked

  • You may launch the application, see the Profile Manager and receive a message that the selected profile is already "in use".

If you experienced this problem and created a new profile and your settings and personal data such as bookmarks mail and passwords are now missing, you can use the Profile Manager to return to your original profile. If Mozilla Suite or SeaMonkey is open, simply click "Tools -> Switch Profile" to select another profile.

  • In Firefox 1.5 or later, a "Close Firefox" dialog box may appear with one of these messages:
    • "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system."
    • (Mac OS X) "A copy of Firefox is already open. Only one copy of Firefox can be open at a time." [1]
  • In Thunderbird 1.5 or later, a similar "Close Thunderbird" dialog box and message, as shown above for Firefox, may appear.

How to unlock your profile

Your profile may be inaccessible for a number of reasons, most often because the application failed to shut down completely the last time it was used and the task or process is still "running in the background", even though there are no open application windows. Ending the running process is normally sufficient to unlock the profile. If the profile remains inaccessible, try these other solutions:

End processes

Go through your task or process list to see if multiple instances of the Mozilla application are still running or not responding and end each instance found.

Remove the profile lock file

The application may have shut down abnormally, leaving the lock in place. To fix this, open the profile folder and delete the file,
  • "parent.lock" (Windows),
  • "lock" and ".parentlock" (Linux), or
  • ".parentlock" (Mac OS X)

For Mac OS X: You need to use a free utility like Onyx or Maintain to turn on visibility for invisible files to show ".parentlock". This file contains no information, and deleting it will unlock the profile.

For Windows: If you attempt to delete the "parent.lock" file and receive the error, "Cannot delete parent: The file or directory is corrupted and unreadable", restart the computer and run the error-checking tool Chkdsk (Windows 2000, XP) or ScanDisk (Windows 98, ME) [2].

Check the profile folder name and location

If Firefox or Thunderbird cannot find the profile folder it will report that the profile is in use or, in Firefox 1.5 or Thunderbird 1.5 and later, that it is already running. This can happen if you delete, rename or move the profile folder, if you run Firefox or Thunderbird from removable media, or if the profile folder is stored on a network drive (bug 278860).

Firefox and Thunderbird look for the profile folder based on the information stored inside the profiles.ini file (see the linked article for details). You use a text editor such as Notepad to open the "profiles.ini" file to see what information it contains. Here is an example:



IsRelative=1 indicates a relative path in the expected profile location, as above.

IsRelative=0 indicates a custom (absolute) profile location, for example, someone might use this to put their profile on a thumb drive or removable disk:


Either edit the "profiles.ini" file to show the changed profile folder location or restore the profile folder to its original name and location.

Important: If you deleted your only profile folder, have no backup to restore and are now seeing the "already running" dialog box, delete or rename the profiles.ini file (or its parent Firefox or Thunderbird folder) in the profile folder path. A new default profile will be created when you next start Firefox or Thunderbird.

Check access rights

This problem can also occur if you don't have the rights to edit the files in the profile (or create the lock file in the first place). Please note that this can happen if you try to use a profile from a filesystem mounted with read-only (e.g. a remote Windows share which doesn't have "allow network users to change my files" checked). This can be pretty tricky to diagnose because there is no lock file in the profile, yet the same message appears (profile in use). Incidentally, Linux users may have ~/.thunderbird and/or ~/.mozilla-thunderbird in their home directories if they have had more than one version of Thunderbird installed.

Check for other applications using the profile

Netscape 7 or another Mozilla-based program may be using the profile. Try shutting down this program to unlock the profile. Additionally, you should create separate profiles for each different application. Especially if you use both Mozilla Suite and Netscape 7, corruption can result from sharing the same profile between two different programs. (This problem is unlikely with Firefox and Thunderbird, since they do not share profiles with other applications in the way that Mozilla Suite and Netscape 7 can share profiles.)

Restoring data from a locked profile

If you are unable to unlock the profile using the above methods, use the Profile Manager to create a new profile and migrate your data from the locked profile to the new profile.

See also