First, let’s address the elephant in the room. Out of the box, the free, open-source version of QCAD (the Community Edition) does not open .dwg files. Why? Because DWG is a proprietary, closed standard owned by Autodesk. Implementing a clean-room reverse engineering of DWG is incredibly difficult and legally risky.
To solve this, the team behind QCAD (RibbonSoft) did something smart. They licensed the Open Design Alliance (ODA) libraries—the industry standard for reading/writing DWG files without using Autodesk’s code. qcad dwg plugin
This license isn’t free. So, that cost is passed down to the user via the QCAD Professional package, which includes the DWG plugin. First, let’s address the elephant in the room
The free community version of QCAD does not support DWG. You must buy QCAD Professional. Is it worth it
Is it worth it? If you open one DWG file per year, no. Use an online converter (at your own security risk). If you open DWG files weekly, yes. €49 is the price of a nice dinner. Compare that to an AutoCAD subscription ($220/month) or even DraftSight ($299/year). The QCAD DWG plugin is an absolute steal.
# Linux example
unzip qcad-dwg-plugin-linux.zip
cp libdwg*.so /opt/qcad/plugins/
# Restart QCAD → File → Open → select .dwg
QCAD is a 2D tool. If you open a 3D DWG file (e.g., a solid model from Inventor or SolidWorks), the plugin will flatten it. You will see the 2D projection or wireframe, but you cannot edit 3D solids.