OBJ vs STL: what is the practical difference?
Both formats can represent polygonal 3D geometry, but OBJ carries more descriptive mesh data while STL is intentionally minimal. Choose based on what must survive the exchange, not only on file size.
What STL stores
STL describes a triangulated surface. In the common workflow it does not reliably carry units, UV coordinates, material libraries or texture references. That makes it predictable for simple shape exchange and 3D printing, but limited for visual assets.
What OBJ adds
OBJ can describe vertices, polygon faces, normals and UV texture coordinates. It can reference a separate MTL file for materials. This makes it more appropriate when the receiving workflow needs surface mapping or a richer model structure than a bare triangle soup.
Compatibility versus richness
STL's minimal structure produces excellent compatibility in manufacturing and printing tools. OBJ also has broad support, especially in graphics and content-creation tools, but a complete visual transfer may require several companion files.
- Use STL for a simple printable mesh when appearance metadata is irrelevant.
- Use OBJ when normals, UVs or material references matter.
- Use 3MF when you want a single modern manufacturing package with units and richer resources.
Why visual inspection still matters
Exports can flip axes, omit components, change scale conventions or lose material references. Opening the exported file in an independent viewer is a cheap quality-control step before you share it or hand it to another workflow.