What is a DWG file?

By Tiago Almeida · Updated 30 October 2026

A DWG file is a drawing saved by AutoCAD, or by another CAD program that works in AutoCAD's format. Architects, engineers, surveyors and fabricators send them back and forth, and a .dwg is often the original behind a PDF plan or a DXF for cutting.

DWG Viewer, our Mac app, opens DWG files, so weigh that in where it comes up.

What DWG means

DWG is short for drawing. It has been AutoCAD's own file format since the first version of AutoCAD in December 1982, and Autodesk calls it the native format for AutoCAD-based products.

A DWG holds the whole drawing as AutoCAD sees it. That includes the model, with its lines, arcs, text, hatches, dimensions and blocks, along with every layer and style, the paper-space layouts that get printed, and any 3D solids and surfaces.

Why some programs can't open DWG files

DWG is a binary format, and Autodesk has never published its specification, so other software has to get at it another way. Autodesk licenses its own library, RealDWG, to some developers. The Open Design Alliance, a non-profit, worked out the format itself and sells its libraries to members, and many CAD apps, such as BricsCAD and DraftSight, read and write DWG that way.LibreDWG, a free GNU project, reads most DWG files too, though it's still in beta and only writes older versions.

That's why laser and CNC software tends to ask for DXF, which Autodesk does document; What is a DXF file? explains the difference. It's also why AutoCAD LT can warn that a drawing wasn't saved by Autodesk software. That warning, called TrustedDWG, tells you where the file came from, not that anything is wrong with it.

DWG versions

AutoCAD doesn't change its file format every year. A new DWG version arrives every few releases, and every AutoCAD from 2018 to 2027 saves the same 2018 format. A DWG file starts with a six-character code that names its version, so a file that begins with AC1032 is a 2018 DWG.

Format	Saved by	Version code
2018	AutoCAD 2018 to 2027	AC1032
2013	AutoCAD 2013 to 2017	AC1027
2010	AutoCAD 2010 to 2012	AC1024
2007	AutoCAD 2007 to 2009	AC1021
2004	AutoCAD 2004 to 2006	AC1018
2000	AutoCAD 2000 to 2002	AC1015
R14	AutoCAD R14	AC1014
R13	AutoCAD R13	AC1012
R11 and R12	AutoCAD R11 and R12	AC1009

Older software can't open a newer DWG. Someone on AutoCAD 2012 who's sent a 2018 DWG gets an error, and the fix is to save the drawing down to an older version.

Converting DWG files

You can turn a DWG into an older version, a DXF or a PDF without AutoCAD:

ODA File Converter, from the Open Design Alliance, converts whole folders between DWG and DXF versions on Mac, Windows and Linux. It's free for non-commercial use.
DWG TrueView, Autodesk's free viewer, saves DWG files in older versions, down to R14, but it only runs on Windows.
DWG Viewer, our app, saves a DWG as a DXF and exports it to PDF or SVG at 1:1 scale.

For PDFs, How to convert a DWG to PDF on a Maccovers every option.

How to open a DWG file on a Mac

macOS can't open DWG files on its own. AutoCAD for Mac and AutoCAD LT for Mac open and edit them, and so do BricsCAD, DraftSight and ARES Commander; AutoCAD for Mac compares them.

To look at a drawing without a CAD subscription, DWG Vieweropens DWG files from AutoCAD R12 up to today's 2018 format, in 2D and shaded 3D, with Finder thumbnails and a space-bar preview. It shows the model rather than the paper-space layouts, can't edit, and costs $19 once. Autodesk Viewer opens DWG files for free in the browser once you upload them. How to open AutoCAD .dwg files on a Mac compares every option.

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DWG Viewer is not made by or affiliated with Autodesk, Inc. Autodesk, AutoCAD, DWG, DXF, DWF, Revit and Inventor are trademarks of Autodesk, Inc.