Recovering a DWG file that refuses to open

A DWG is a binary file with a tightly packed structure. An interrupted download, a full disk or a save that never finished can leave it unreadable. The good news is that usually only part of the file is damaged, and the rest is still in there.

What to try, in order

1. Look for the backup. AutoCAD leaves a .bak file beside the drawing on every save. Rename it to .dwg and open it — in most cases that single step is enough.
2. Check autosave. Files ending in .sv$ sit in the temp folder and usually cost you no more than a few minutes of work.
3. Run RECOVER. AutoCAD's own repair command tries to read the file and discard the damaged objects.
4. Step down the version ladder. Try converting the file to an older DWG version. The damaged part is often in a section specific to a newer release, and converting down skips it.
5. Convert to DXF. Because DXF is text it can be read partially: the broken section is skipped and the rest survives.

What the version ladder is

The DWG format has been through many releases — R12, R14, 2000, 2004, 2007, 2010, 2013, 2018 — each adding new sections. When a file will not read, converting it while stepping the target version down often works: with the section specific to the newest release skipped, the geometry usually comes out intact.

What to check in a recovered file

• Layer count. Fewer layers than you expected can mean a section was skipped.
• Block references. Are the door, window and furniture blocks in place, or empty?
• Title block and text. Text objects are the most fragile part — is the project name still there, and are the grid letters?
• Extents. If the drawing extents are absurdly large — millions of units — a stray object probably landed at the origin during recovery.

Avoiding a repeat

Open and save large files locally rather than on a network drive, and copy them across when you are done. On long sessions, save intermediate versions under new names. And keep a scaled PDF alongside every issued sheet: even if the drawing file is lost, the visual record of the project survives.