STL describes a surface as triangular facets. It is widely used to exchange models with slicing and mesh-processing applications, but the geometry alone does not establish that a model is a closed, intersection-free solid or suitable for a particular printer.
- Geometry
- Triangle facets with vertex coordinates and facet normals; ASCII and binary encodings are common.
- Units
- No standard physical-unit field. A coordinate value needs an intended unit supplied by the source workflow.
- Appearance
- No standard texture or material system. Nonstandard binary color conventions are not used by this workbench.
- Structure
- No CAD features, scene hierarchy or manufacturing build instructions.
STL or 3MF for a printing workflow?
STL is useful when you need only triangle geometry and can agree on units separately. A supported 3MF workflow can carry a declared physical scale and more manufacturing information. Converting a 3MF package to STL discards those package semantics; it does not make the model more accurate.
Changing the container does not rebuild the model
STL→OBJ and STL→PLY retain the existing triangles. STL→GLB additionally requires you to declare their physical scale. None of these operations recover original CAD surfaces, textures or design history. Keep an editable source model when one exists.