What is an AutoCAD file?

An AutoCAD file is usually a DWG, the drawing format of AutoCAD, Autodesk's commercial 2D and 3D CAD program. Around each drawing it also writes templates (DWT), standards files (DWS), backups (BAK), autosaves (SV$), lock files (DWL), and exchange files (DXF), and each extension tells you what the file is for.

What AutoCAD is

AutoCAD is a drafting and design program from Autodesk, first released in 1982 and used for architectural plans, mechanical parts, site layouts, and electrical schematics. It runs on Windows and macOS, and AutoCAD LT is a lighter edition for 2D work. Because it has been an industry standard for decades, its DWG format became the common language for exchanging drawings, and many other CAD programs read and write it.

That is why "AutoCAD file" in everyday use means a DWG. If someone sends you one, you do not need the program to look at it: a viewer such as the one on this page opens it in the browser.

AutoCAD also comes with specialized toolsets for architecture, mechanical design, electrical schematics, and civil engineering, and all of them save drawings as DWG. A drawing from one of these toolsets can contain custom objects, such as walls or pipe runs, that a plain viewer shows as simple lines or leaves out. If parts of a plan seem missing, ask the sender for a copy exported to plain AutoCAD objects.

AutoCAD file extensions

Recover a drawing from BAK or SV$

When AutoCAD crashes or a drawing is saved over by mistake, the backup files are the way back. The BAK file next to the drawing holds the version before the last save. The SV$ file in the temp folder holds the last automatic save, made every few minutes by default. Both are ordinary drawings with a different extension.

Copy the file, rename the copy to end in .dwg, and open it. You can check its contents first by dropping the renamed copy into the viewer here, which also shows whether the backup is newer than you feared. The DWG version inside follows the program that saved it; DWG versions explains the codes.

Which file to send, and AutoCAD files vs DWG

For someone who will edit, send the DWG, saved in a version they can open. If the drawing uses external references, fonts, or images, package it with eTransmit so the support files travel with it. For someone who will only look, a PDF or a link to a browser viewer is enough. Templates, plot styles, and lock files are internal to the office that made them and rarely need to leave it.

This page is about the set of files the program writes. For what is inside the drawing format itself, its structure and history, see what is a DWG file, and for the exchange format, what is a DXF file. To view one without the program, see how to open a DWG file without AutoCAD.

AutoCAD and DWG TrueView are trademarks of Autodesk, Inc. DWG Viewer is an independent browser tool and is not affiliated with, sponsored by, or endorsed by Autodesk.

Frequently asked questions