An SMG file is a 3D CAD model saved in the SolidWorks Composer file format. It contains a 3D assembly, which may include one or more parts or sub-assemblies. SMG files also store document properties, which include information about the coordinate system and textures of the assembly.

SolidWorks Composer is a technical documentation program used to communicate information about a product using 3D product design data. SMG files are created from 3D CAD models designed in SolidWorks. The files are exported from SolidWorks then imported into SolidWorks Composer to create the technical documentation for the 3D CAD models. To open an SMG file in SolidWorks Composer, select File → Open, choose the SMG file, and click Open. To create an SMG file in SolidWorks, select File → Save As, choose SolidWorks Composer (*.smg) from the Save as type dropdown menu, and click Save.