Files with undo file extension are usually used by many applications for their backup files.
UNDO file extension - Backup data
What is undo file? How to open undo files?
File type specification:
The .undo file extension is probably used by some applications for their backup files (documents, spreadsheets, projects, designs, images, etc.) during some process, so its possible to roll-back the changes.
This undo file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.
