Biggest library of free 3D models on this planet (universe?).
Check the copyright however for commercial usages.
Thingiverse functions as a primary open-source repository for digital design files tailored for additive manufacturing and rapid prototyping. The platform facilitates the distribution of STL, OBJ, and SCAD files, enabling a global community to share, iterate, and document mechanical designs under Creative Commons licensing. It provides a structured environment for versioning through its remixing capabilities and offers integrated parametric modeling tools, allowing users to adapt existing geometries for specific functional requirements, assembly instructions, and hardware configurations.
