BAK1 file extension - Backup file
What is bak1 file? How to open bak1 files?
File type specification:
The bak1 File extension is for a long time used for backups.
Generally a *.bak1 file is a backup of original file, when the original extension is renamed to somename.bak1.
So, to restore original file, rename file to its original extension, if you know it, that is.