A DWG file is a proprietary digital format primarily used for storing two-dimensional (2D) and three-dimensional (3D) design data created by AutoCAD and other CAD programs. Since AutoCAD requires a license, you can open DWG files without it using dedicated DWG viewer applications, certain free CAD software, or online conversion/viewing services. These alternatives provide access to view, measure, and sometimes perform light editing on the drawings, differing from AutoCAD itself which offers full creation and advanced modification capabilities.

For instance, Autodesk provides a free online viewer (Autodesk Viewer) where you can upload DWG files to examine them in a web browser. Alternatively, you can install free desktop applications like LibreCAD (for 2D primarily) or draftSight Free (check current features) to directly open and view, and potentially make minor edits to, DWG files locally. Engineers, architects, contractors, and hobbyists often use these tools to review plans and shop drawings when only viewing or basic interactions are needed.

Key advantages include cost savings and accessibility, as many viewers are free and work on various devices. However, limitations exist: feature support varies significantly between free viewers and AutoCAD, advanced editing or specialized tools are usually unavailable, and performance may lag with complex drawings. Ethically, ensure you have permission to view the file. The availability of robust free viewers is constantly improving, making sharing and reviewing CAD data easier for stakeholders without full AutoCAD licenses.