If you just need to quickly edit an old .123dx file you have lying around, go ahead and install the legacy version. But for new projects? Save yourself the headache. Embrace the modern tools.

Since 123D Design is effectively obsolete, most Mac users have migrated to these contemporary options:

Autodesk 123D Design for Mac was officially . While the software is no longer officially supported or available for direct download from Autodesk, it remains a beloved legacy tool for hobbyists due to its intuitive "drag-and-drop" approach to 3D modeling. Status & Modern Compatibility

However, as Autodesk's portfolio grew complex, they consolidated these features into newer platforms: The web-based "introductory" successor. Fusion 360: The advanced, professional-grade alternative. 123D Apps: 123D Design, Sculpt+, Make, and Catch | Autodesk