.BACKUP File Extension
What is a BACKUP file?
A BACKUP file contains a backup created by various Android phones and tablets. It stores user information, such as contacts and user files, and is useful for archiving save points from your mobile device so the data can be restored if a problem occurs with the device. The BACKUP format has been replaced by the .AB format.
In the past, Android users could create BACKUP files by accessing their device's System Recovery Mode and selecting the option to back up their data. When the backup process finished, the BACKUP file(s) were saved to the Android device's SD card.
You will most likely encounter an Android BACKUP file only on the SD card of an Android device. Therefore, if you discover a BACKUP file on your computer, it was most likely created by a program on your computer, and is not an Android BACKUP file.
NOTE: Some Android devices split users' data across multiple BACKUP files, with extensions such as .BACKUP1, .backup2, and so on.
Common BACKUP Filenames
userdata_yyyymmdd_HHMMSS.backup - A BACKUP file, saved with a filename that includes the date and time at which the file was created.
How to open a BACKUP file
To restore a BACKUP file, first hold the power button and volume button on your Android device to start the device in System Recovery Mode. Then, select the option to restore user information from the System Recovery menu.