.OLD File Extension

Typically used as an indicator for a backup copy of a file; appended to the filename when a newer version of the file has been created or saved by a certain program; often placed after the original file suffix (i.e. document.doc.old would be a backup copy of the file "document.doc").

May be created automatically by a software program, but may also be created manually by the user. The ".old" extension may have to be deleted in order for the file to open correctly.