DWG is a proprietary binary file format used for storing two- and three-dimensional design data and metadata. It is the native format for several CAD (Computer-Aided Design) packages, most notably AutoCAD, and is a common format for sharing design data between different CAD applications. DWG files contain a complex structure of objects, including lines, arcs, circles, text, dimensions, and 3D solids. They can also store information about layers, blocks, and other design elements. The format is highly optimized for efficient storage and retrieval of large amounts of graphical data. Because it is a proprietary format, accessing and manipulating DWG files often requires specialized software or libraries. While Autodesk provides a free DWG viewer, full editing capabilities typically require a paid license for AutoCAD or a compatible CAD program. The DWG format has evolved over many years, with different versions of the format being used by different versions of AutoCAD. This can sometimes lead to compatibility issues when opening DWG files created with newer versions of AutoCAD in older software. The Open Design Alliance (ODA) has reverse-engineered the DWG format and provides libraries for reading and writing DWG files, allowing other software vendors to support the format without licensing technology from Autodesk.