From MozillaZine Knowledge Base

This article was originally written for Thunderbird but it also applies to Firefox and Mozilla Suite.

MozBackup is a standalone utility (for Windows only) rather than a Thunderbird extension. It works by backing up a Thunderbird profile into a single file (named "*.pcv"), which can then be restored on the same Windows computer or a different one. (MozBackup can also be used to back up and restore Firefox, Mozilla Suite, and Netscape 7 profiles.) It can be downloaded from the MozBackup homepage, where additional MozBackup documentation is also available. The download web page lists what extensions it knows how to back up/restore.

While Mozbackup is extremely popular in the forums, it's recommended that - if you plan on using it for regular backups - you first test it to verify that it will properly restore your Thunderbird profile.


Backing up

  1. If Thunderbird is running, exit the application.
  2. After downloading and installing MozBackup, launch the utility, choose the "Backup" option and follow the instructions.
  3. At the bottom of the next screen you can specify the location of the backup file ("*.pcv") that will be created. Take note of where the file will be saved.
  4. Click on through the remaining screens until the .pcv file has been created. Then burn this file onto a CD or store it elsewhere for safekeeping.


  1. Make sure Thunderbird has been installed on the computer. If it has not been launched yet, it is probably best to launch it once to make sure the "registry.dat" file has been created. Exit Thunderbird before proceeding.
  2. Launch MozBackup, choose the "Restore" option, and follow the instructions.
  3. The next screen will prompt you, "Select the profile you want to restore." Important: the profile you select will be overwritten by the contents of the profile that is backed up in the ".pcv" file. If you do not want to overwrite any of the profiles listed in the MozBackup screen, you should create a new profile by clicking on the "New Profile" button (you may need to click on the "Refresh" button afterwards) or if this doesn't work you can exit MozBackup, create a new profile with the Thunderbird Profile Manager and launch MozBackup to begin the restore process again.
  4. Select the ".pcv" file that contains your backed-up profile. If you are restoring to a different computer you will need to transfer the ".pcv" file to that computer first.
  5. Click on through the remaining screens until the profile has been restored and exit MozBackup.
  6. Launch Thunderbird. The restored profile should now be available for use.

Note that if extensions are included in the backup and restoration, the version of Thunderbird should be the same. For instance, if a profile (including extensions) is backed up from an installation of Thunderbird v 0.9 and restored to an installation of Thunderbird 1.0.5, the old extensions may cause errors at runtime of the newer version. To alleviate this, exclude (uncheck) "Extensions" on the "Select the details you want to restore:" page. You will have to reinstall new versions of the extensions from the Mozilla Update Site.

Automating backups

Mozbackup supports command line arguments to specify what it should back up. This means you can schedule backups using the Windows task scheduler. See this web page for more information.

Problems restoring with MozBackup?

If you get a "Zip file could not be opened" error message use 1.5 alpha1 of Mozbackup to restore it. This is a known problem that should be fixed in version 1.5 of Mozbackup.

If you are having problems restoring a ".pcv" backup file that you created with MozBackup and nothing seems to work, keep in mind that the ".pcv" file is actually a normal ".zip" file.

  1. Rename the backup file from "*.pcv" to "*.zip".
  2. Extract (unzip) the ".zip" file into a convenient location. If you look inside the unzipped folder you will see your mail folders, address books and the other files that make up your profile folder.
  3. Manually restore/migrate this unzipped profile folder as described here.

Your unzip utility will do a CRC check of the files within the .zip file. If they don't match it will report the .zip file is corrupt, and won't let you extract them. If this happens try using a program such as DiskInternals ZIP Repair.

How to set the default folder for backup files

If you want to set the default folder for your backup files, go to the MozBackup program folder and find the file named "backup.ini". In this file you can set the default backup folder, as a general setting and/or for specific Mozilla applications.

See also