.UNL File Extension

Backup file created by MapSource, a program used to manage maps for Garmin navigational devices; contains unlock codes for maps; used as a backup copy so that the codes can be restored back to the Garmin device.

To create a UNL file in MapSource, select Utilities → Unlock Maps, click "Next," and choose "Backup my unlock codes to a file." To reload unlock codes, select Utilities → Unlock Maps, click "Next," select "Retrieve and reinstall all my unlock codes, click "Next," and then select "Retrieve my unlock codes from a file on my PC."

NOTE: Unlock codes are specific to a single GPS unit purchased from Garmin. Therefore, it is not possible to use a UNL file to unlock maps on multiple Garmin devices.