Quick Answer

An AutoCAD BAK file is an automatic backup copy of a DWG drawing. Every time you manually save a drawing, AutoCAD can create a .BAK file containing the previous saved version of the drawing.

To recover it:

1. Locate the .BAK file.
2. Rename the extension from .BAK to .DWG.
3. Open the file in AutoCAD.
4. Run AUDIT to verify and repair the drawing database.

If AutoCAD crashed before the last manual save, check the Drawing Recovery Manager and SV$ AutoSave files, which may contain newer data than the BAK file.

What Is a BAK File in AutoCAD?

A BAK file is a backup copy of a drawing created during the save process.

Example:

SitePlan.dwg
SitePlan.bak

The DWG file is the current drawing.

The BAK file is the previous saved version.

This provides a local rollback point if:

• A drawing becomes corrupted
• Geometry is accidentally deleted
• Layers are modified incorrectly
• A save operation fails
• AutoCAD crashes
• A network interruption damages the active file

By default, the BAK file is stored in the same folder as the DWG file.

How AutoCAD Creates BAK Files

AutoCAD does not overwrite the existing DWG file directly.

The save process follows this sequence:

Current Drawing Session
          │
          ▼
User Executes QSAVE
          │
          ▼
Existing Drawing.dwg
          │
          ▼
Renamed to Drawing.bak
          │
          ▼
New Drawing.dwg Written

STEP 1 — The User Saves the Drawing

The process starts when the user executes:

QSAVE

or clicks Save.

AutoCAD then prepares to replace the existing DWG file.

Note: A SAVEAS operation behaves differently. When you save a drawing under a completely new filename, AutoCAD does not create a BAK file for the new drawing because no previous version exists yet. The original drawing retains its own BAK history.

STEP 2 — The Existing DWG Is Renamed

The previous version of the drawing:

Drawing.dwg

is renamed:

Drawing.bak

Any older BAK file is replaced.

STEP 3 — A New DWG Is Written

AutoCAD writes a brand-new DWG file containing the current database.

Result:

Drawing.dwg  → Current Version
Drawing.bak  → Previous Saved Version

A BAK file normally represents the last disk version of a drawing before the most recent save operation.

When a BAK File Can Save a Project

BAK files are often the fastest recovery method when:

• A drawing becomes corrupted after a save
• Someone accidentally saves unwanted changes
• Geometry disappears unexpectedly
• Layer standards are damaged
• Third-party add-ins corrupt the database
• A network write operation fails

In many situations, the BAK file opens successfully even when the current DWG does not.

How to Recover an AutoCAD BAK File

STEP 1 — Close AutoCAD

Close all AutoCAD sessions.

This releases any active:

DWL
DWL2

lock files.

STEP 2 — Show File Extensions

Windows hides known file extensions by default.

Windows 11

1. Open File Explorer.
2. Click View.
3. Click Show.
4. Enable File Name Extensions.

Windows 10

1. Open File Explorer.
2. Click View.
3. Click Options.
4. Open the View tab.
5. Disable:

Hide extensions for known file types

6. Click Apply.

STEP 3 — Locate the BAK File

Navigate to the folder containing the drawing.

Example:

SitePlan.dwg
SitePlan.bak

STEP 4 — Rename the File

Rename:

SitePlan.bak

to:

SitePlan_Recovered.dwg

Using a different filename prevents accidental overwriting of the production drawing.

Accept the Windows warning regarding file extensions.

STEP 5 — Open the Recovered Drawing

Open the newly renamed DWG file in AutoCAD.

If the drawing opens successfully, immediately save a new copy.

STEP 6 — Run AUDIT

After the drawing opens:

Type:

AUDIT

Press Enter.

When prompted:

Fix any errors detected?

Enter:

Y

AutoCAD will scan and repair database errors found within the drawing.

Using RECOVER to Repair a Damaged Drawing

The RECOVER command works differently from AUDIT.

Unlike AUDIT, RECOVER cannot be run on the drawing that is currently open.

Instead, AutoCAD must open the file through the RECOVER process itself.

STEP 1 — Close the Recovered Drawing

Close the drawing you previously opened.

STEP 2 — Open a Blank Drawing

Open AutoCAD and start a blank drawing.

STEP 3 — Run RECOVER

Type:

RECOVER

Press Enter.

STEP 4 — Select the Damaged Drawing

Browse to the recovered DWG file.

Select it.

AutoCAD will:

• Open the drawing
• Scan the database
• Repair recoverable errors
• Generate a recovery report

STEP 5 — Review the Results

After RECOVER finishes:

• Save the drawing
• Run AUDIT again if necessary
• Verify geometry, layers, blocks, and external references

For drawings containing Xrefs, use:

RECOVERALL

which checks both the host drawing and attached references.

Drawing Recovery Manager

If AutoCAD crashes unexpectedly, this should be your first recovery method.

Type:

DRAWINGRECOVERY

if the palette does not open automatically.

The Drawing Recovery Manager displays:

• DWG files
• BAK files
• SV$ files

associated with the crash session.

Because it automatically identifies the most recent recoverable version, it is usually faster than manually searching through temporary folders.

Recovering an AutoCAD SV$ AutoSave File

If the BAK file is too old, an AutoSave file may contain more recent changes.

What Is an SV$ File?

An SV$ file is an automatic snapshot created at scheduled intervals while you work.

Unlike BAK files, AutoSave files do not require a manual save operation.

STEP 1 — Locate the AutoSave Folder

Type:

OPTIONS

Open:

Files

Locate:

Automatic Save File Location

You can also check:

SAVEFILEPATH

to see the current AutoSave directory.

Tip: Press Win + R, type:

%tmp%

and press Enter.

This often opens the folder containing recent AutoSave files.

STEP 2 — Find the Most Recent SV$ File

Look for files ending with:

.sv$

Choose the most recent file based on timestamp.

STEP 3 — Copy the File

Copy the file to a safe location.

Do not work directly inside the temporary folder.

STEP 4 — Rename the File

Rename:

Drawing_1234.sv$

to:

Drawing_1234.dwg

STEP 5 — Open the Drawing

Open the file in AutoCAD.

Run:

AUDIT

after the drawing opens successfully.

What About AC$ Files?

In some crash situations, AutoCAD creates temporary command files using the:

.ac$

extension.

These files are not intended as standard recovery files, but large AC$ files created shortly before a crash may contain recoverable drawing information.

If no SV$ file exists:

1. Locate recent AC$ files.
2. Copy them to a safe folder.
3. Rename the extension to DWG.
4. Attempt to open the file using RECOVER.

Recovery success varies, but it is often worth trying when no other backup exists.

Understanding DWG, BAK, SV$, DWL, and DWL2 Files

DWL and DWL2 Files

These files are created whenever a drawing is open.

They help prevent multiple users from editing the same file simultaneously.

Normally they disappear when AutoCAD closes.

If AutoCAD crashes, they may remain behind and can usually be deleted once you verify no user has the drawing open.

Control AutoSave Frequency

The AutoSave interval is controlled by:

SAVETIME

Example:

SAVETIME = 10

creates an AutoSave file every 10 minutes.

Many CAD managers use:

5

or

10

minutes in production environments.

Redirect BAK Files to Another Folder

Large projects can generate thousands of backup files.

The Express Tool:

MOVEBAK

allows you to redirect BAK files to a dedicated folder.

Example:

C:\AutoCAD_Backups

To restore the default behavior:

Run:

MOVEBAK

Then enter:

.

A single period returns BAK files to the drawing folder.

Why DWG Files Become Corrupted

Common causes include:

• Power failures
• Forced shutdowns
• AutoCAD crashes
• Defective SSD or HDD sectors
• Network interruptions
• VPN disconnects
• Faulty third-party add-ins
• Antivirus file locking
• Storage device failures

Cloud synchronization platforms can also create problems.

Examples include:

• OneDrive
• SharePoint
• Dropbox
• Google Drive

During a save operation, AutoCAD temporarily renames the existing DWG to BAK and writes a new DWG file. Some cloud synchronization agents attempt to access the file during this process, which can interrupt the save sequence or interfere with BAK creation.

For critical projects, work from a local drive and allow synchronization after the drawing session ends.

AutoCAD for Mac: Recovering a BAK File

AutoCAD for Mac also creates BAK files.

STEP 1 — Open Finder

Navigate to the drawing folder.

STEP 2 — Locate the BAK File

Find:

Drawing.bak

STEP 3 — Rename the File

Rename:

Drawing.bak

to:

Drawing_Recovered.dwg

STEP 4 — Open the Drawing

Open the file in AutoCAD for Mac.

STEP 5 — Run AUDIT

Type:

AUDIT

and repair any detected errors.

If the file remains unstable, close it and use:

RECOVER

from a blank drawing.

Best Practices

• Keep ISAVEBACK enabled.
• Set SAVETIME to 5–10 minutes.
• Save frequently.
• Maintain external backups.
• Run AUDIT periodically.
• Use RECOVER when opening damaged drawings.
• Save incremental versions of critical projects.
• Avoid unstable network connections.
• Work locally before syncing to cloud storage.

FAQ

Can AutoCAD Open a BAK File Directly?

No.

Rename the extension from:

.bak

to:

.dwg

before opening it.

Why Is No BAK File Being Created?

The most common reason is:

ISAVEBACK = 0

A BAK file also cannot exist until a drawing has been saved at least once.

What Is the Difference Between BAK and SV$ Files?

BAK files are created during manual saves.

SV$ files are created automatically according to the AutoSave interval.

Can I Delete BAK Files?

Yes.

Deleting a BAK file does not affect the active DWG.

You simply lose the previous saved version.

Why Is My BAK File Larger Than the DWG?

Database cleanup, compression differences, purging operations, and drawing repairs can create size differences between the two files.

This is normal.

Which Recovery Method Should I Try First?

Use this order:

1. Open DRAWINGRECOVERY if AutoCAD crashed.
2. Open the DWG directly.
3. Run RECOVER.
4. Rename and test the BAK file.
5. Run AUDIT.
6. Recover the latest SV$ file.
7. Check recent AC$ files if no other recovery source exists.