What Is a .BK File?
A .bk file showed up next to your document. It is almost always a backup copy an app saved automatically. Here is what made it and whether you need it.
What a .bk file is
A .bk file is a backup — a copy an application saved before overwriting or editing the original file. AutoCAD, note apps, database tools, and many editors write a .bk so you can roll back if something goes wrong.
Why you have one
The app created it on purpose as a safety net. When you saved changes, it kept the previous version as .bk so the last good copy is never lost.
How to open a .bk file
A .bk is just the earlier version of another file, so it opens in the same program that made it. The quickest way: copy it, rename the copy back to the original extension (for example drawing.bk to drawing.dwg for AutoCAD, or .docx/.txt for an editor), then open it normally. If you are unsure of the original type, open it in a text editor to check whether it is readable text.
Is it safe to delete?
Yes, if your current file is fine. The .bk is only a fallback. Keep it until you have confirmed the working file opens and looks correct; after that it is safe to remove.
How to handle a .bk file by OS
Windows: right-click, Rename, change the extension to the original; enable file-extension display in File Explorer first. macOS: rename in Finder and confirm the extension change. Linux: use mv file.bk file.dwg or open directly with the source app.
Common problems
If your main file is corrupted, the .bk is your recovery copy — rename and open it to get the last saved state back.
FAQ
How do I open a .bk file?
Rename a copy to the original file's extension (e.g. .dwg, .docx) and open it in the program that made it. A .bk is just the previous version.
Is it safe to delete a .bk file?
Yes, once you have confirmed your current file is intact. The .bk is only a backup fallback.
What program creates .bk files?
Many do — AutoCAD, editors, and database tools write a .bk backup before saving changes.
Will I lose data if I delete a .bk file?
Only if your main file later fails; the .bk holds the previous saved version, so keep it until you are sure the current file is good.