A DWG file is a database of 2D or 3D drawings created with AutoCAD, a professional CAD program. It contains vector image data and metadata that describes the contents of the file. The file is related to the .DXF format, which is an ASCII version of DWG.
DWG files can be viewed on Windows using Autodesk's free DWG TrueView program. They may also be opened by other third-party applications that support the DWG format.
NOTE: Several variations of the DWG format have been published by AutoCAD. Since 2000, the DWG 2000, DWG 2004, DWG 2007, DWG 2010, and DWG 2013 formats have been introduced. While these formats are similar, their file structures are slightly different. Therefore, third-party CAD programs may be able to open some DWG files, but not others.