How to Open a BAK File (Find What Made It First)
A .bak file is a backup copy, not a single format. Work out which program made it, then let that program restore it. For a simple document backup, copying the file and removing the .bak ending is often all you need.
A file that ends in .bak could have come from almost any program on your computer. That is why there is no single way to open it.
.bak just means “backup.” It is a naming convention, not a format that one program owns.
So the real first step is not opening the file. It is working out which program made this particular one.
The folder it sits in, and the rest of the name, are your best clues.
Match your file to the table below, then follow that section.
| If your .bak… | It is most likely… |
|---|---|
| sits next to a document with the same name | an editor’s automatic backup, so the rename trick usually works |
| is in a database folder and is very large | a database backup, restore it from that database program |
| has a drawing name, or sits with .dwg files | an AutoCAD drawing backup, rename it to .dwg |
| is inside a game or app folder | that program’s own save or settings backup |
| opens in Notepad and shows readable text | a text or configuration backup |
First, figure out what your .bak actually is
Three quick checks usually settle it:
- Where it sits. A .bak next to a document with the same name is probably that program’s own backup. One inside a database or CAD folder points elsewhere.
- The size. A small .bak beside a document is usually a simple backup. A very large one in a database folder is likely a full database dump.
- A peek inside. Right-click the file and open it in Notepad. Readable words near the top often name the program that wrote it.
Most .bak files that are not plain text will show scrambled characters in Notepad. That is normal and does not mean the file is broken.
Close it without saving.
Once you know the likely source, jump to the matching section below.
The rename trick, for a simple backup
The most common case is an editor’s own automatic backup.
A .bak that sits beside a document with the same name is almost always this kind.
- Copy the .bak file, and leave the original untouched.
- Remove the .bak ending from the copy’s name, so report.docx.bak becomes report.docx.
- Open the renamed copy the same way you would normally open that file type.
If you guessed wrong, the untouched original is still right there.
This trick only works if you can actually see the real file ending. Windows hides extensions by default, so here is how to show file extensions in Windows before you rename anything.
Work on a copy, never the original. The original .bak file may be the only surviving copy of your data, so rename or edit a duplicate instead.
Database backups need their own program
Database software can use .bak for its own backups too, and SQL Server is the best known example.
A database .bak is not meant to be opened by hand. Renaming it to something else achieves nothing.
Restore it from inside that same database program instead.
That is the only way to get a working database back out of the file.
AutoCAD drawing backups
AutoCAD leaves its own .bak file next to every drawing it saves.
If yours sits next to .dwg files, or shares a drawing’s name, this is almost certainly one.
Rename the copy’s ending from .bak to .dwg, the same way as the document trick above. Then open it in AutoCAD or another CAD program.
Game and app backups
Some games and apps write their own .bak files as a save or settings backup.
These belong only to that program, and opening them anywhere else shows meaningless data.
Keep the file where the game or app expects to find it. Moving or renaming it can break the very save it is meant to protect.
When to delete a .bak file
A .bak file is only useful as a safety net for the original.
Do not delete it until you have confirmed the original file is present and working.
Being the surviving copy is the entire purpose of the file.
Once the real file opens fine on its own, an old .bak is usually safe to remove.
That same detective work applies to other files that are not one single format either. A stray .dat file calls for the same approach, so find the source first.
A quick safety note
You do not need a special “.bak opener” program.
The right tool is always whatever created the file, whether that is a text editor, AutoCAD, or a database program.
Sites that advertise a universal .bak opener often bundle adware or worse. Skip them and stick to the software already mentioned above.
Frequently asked questions
What program opens a .bak file?
There is no single program. Whatever software created your particular backup, such as a text editor, AutoCAD, or a database tool, is the one that can actually use it.
Can I just delete .bak files?
Only once you are sure the original file is present and working. A .bak’s entire job is to be that safety copy, so do not delete it while you might still need it.
How do I turn a .bak back into the original file?
For a simple document backup, copy the file and remove the .bak ending. Database and CAD backups need their own program to restore or rename them properly instead.
Why does my computer keep making .bak files?
Many editors and tools automatically save a backup copy before every change. That automatic habit is what fills a folder with .bak files over time.
Is a .bak file a virus?
No. .bak is just a common naming convention for a backup, not a program or a virus. Still, treat any unexpected file from an unknown source with caution.
