Can’t Open Bak File AutoCAD?

A .bak file in AutoCAD is a backup copy of a drawing. If you can’t open it directly, the usual fix is to rename the file extension and, if necessary, use AutoCAD recovery tools. Below is a beginner-friendly, step‑by‑step guide with alternatives, common errors and fixes, and practical tips to successfully open and recover .bak files.

Intro — what is a .bak file and why it matters

A .bak file is an automatic backup created by AutoCAD when saving a drawing (DWG). It contains a previous version of your drawing and can save you if the main .dwg becomes corrupted or lost. To make the file usable in AutoCAD you usually need to rename .bak to .dwg and then open or recover it.

How to open a .bak file in AutoCAD — step‑by‑step

Step 1 — show file extensions (Windows)

Open File Explorer.
Click the View tab → check File name extensions (Windows 10/11) or go to Folder Options → View → uncheck “Hide extensions for known file types”.
Now you can see the “.bak” extension.

Step 2 — make a copy first

Right‑click the .bak file → Copy, then paste in the same folder or another safe location.
Always work on a copy to avoid losing data.

Step 3 — rename the extension

Right‑click the copied file → Rename.
Change the extension from .bak to .dwg (for example, mydrawing.bak → mydrawing.dwg).
Confirm the change when Windows warns about changing file extensions.

Step 4 — open the renamed file in AutoCAD

In AutoCAD, use File → Open and select the renamed .dwg file.
If AutoCAD opens it cleanly, save it with a new name.

Step 5 — if AutoCAD can’t open it, use recovery tools

Use the RECOVER command: Type RECOVER in the command line, then select the renamed .dwg. This attempts to repair corrupt elements.
If RECOVER runs but issues remain, run AUDIT after opening (or use the Drawing Recovery Manager via the application menu: Application Menu → Drawing Utilities → Drawing Recovery).
Use Open and Repair (right‑click the file in the Open dialog and choose this if available).

Alternative methods when renaming fails

Use DWG TrueView (free from Autodesk) to view and convert DWG files. It can sometimes open files that AutoCAD struggles with and can convert to a different DWG format.
Upload to the Autodesk Viewer (web) to check if the drawing content is intact.
If you have the original .dwg that created the .bak, try opening that instead.
Look in the AutoCAD autosave folder for .sv$ files (rename .sv$ to .dwg) — these are autosave versions and may have usable data.
Use third‑party DWG recovery tools only from reputable vendors; scan downloaded tools for malware first.
If the .bak file is on a network drive, copy it locally before renaming/opening to avoid network-related locks.

Common errors and how to fix them

“Not a valid DWG file” or “File is corrupted”
- Run RECOVER and AUDIT.
- Try opening in DWG TrueView or Autodesk Viewer.
- If the file size is 0 bytes, the file is irrecoverable — check other backups.
File extension won’t change / still shows .bak
- Ensure file name extensions are visible (see Step 1).
- Confirm you have write permissions on the file/folder.
AutoCAD says “Drawing created by a newer version”
- Open the file in a matching or newer AutoCAD version, or use DWG TrueView to convert it.
- Save it down to an older DWG format if needed.
File opens read‑only or locked by another user
- Check file properties and remove Read‑only attribute.
- Close any process or user that may be locking the file; copy the file locally.
Antivirus or OS blocks opening
- Temporarily whitelist the file or folder in your antivirus (only if you trust the file).
- Scan the file for malware before disabling protections.
Hidden or missing autosave/backups
- Check AutoCAD Options → Files tab → Automatic Save File Location to find autosave (.sv$) files.
- Search your system for .bak or .sv$ if you don’t find the expected file.

Practical tips and best practices

Always make a copy of the .bak before renaming or attempting repairs.
Keep regular backups and enable AutoCAD’s autosave (set an interval in Options → Open and Save).
Use version control or cloud storage (Dropbox, OneDrive) with file versioning for extra safety.
When renaming, type the new extension carefully: .dwg (not .doc or other common extensions).
Keep AutoCAD updated and use DWG TrueView to check file compatibility.
If you suspect disk corruption, check the drive with chkdsk or disk utility before working on files.

FAQ

How do I convert a .bak to .dwg safely?

Rename a copy of the .bak file to .dwg in File Explorer. Always work on a copy and then open the renamed file in AutoCAD or DWG TrueView. If it doesn’t open, use the RECOVER command.

What if AutoCAD shows “drawing is not valid” after renaming?

Run RECOVER and then AUDIT. If that fails, try DWG TrueView, Autodesk Viewer, or other recovery utilities. If file size is 0 bytes, the file is likely unrecoverable.

Can I open a .bak file without AutoCAD?

Yes — use DWG TrueView (free) to view or convert the file, or upload it to the Autodesk Viewer online. Other CAD viewers may also work.

Where are AutoCAD backup and autosave files stored?

Check AutoCAD Options → Files → Automatic Save File Location (for .sv$ files) and Backup File Location (for .bak files). You can also search your system for .bak and .sv$.

Is it safe to rename .sv$ or other extensions to .dwg?

Yes — for autosave files (.sv$) and backups (.bak), renaming a copy to .dwg is standard practice. Always work on copies first.

What causes .bak or .dwg files to corrupt?

Common causes: sudden power loss, disk errors, network interruptions, improper program termination, or malware. Keeping backups and using stable storage reduces risk.

Can older AutoCAD open files saved by newer AutoCAD?

Not directly. Use DWG TrueView to convert newer DWG files to an older format, or open the file in the newer version and save it to the older DWG format.

My file is on a network drive and won’t open — what now?

Copy the .bak to a local drive, then rename and open locally. Check network permissions and ensure no one else has the file locked.