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What is it
STL is a 3D model format that describes an object's surface as a mesh of triangles — the universal input format for 3D printers and slicing software. The 3D printer's language. No colour, no texture, no material information, just geometry. This simplicity is why every slicer (Cura, PrusaSlicer, BambuStudio) accepts STL, every CAD program exports it, and every online 3D printing service expects it. The format dates back to 1987 and stereolithography (hence the name). For anything beyond basic geometry — colour, multiple materials, metadata — the newer 3MF format is superior, but STL's dominance in the 3D printing community shows no signs of fading.
Technical details
Safety
What opens it
Cura
PrusaSlicer
Blender
Windows 3D Viewer
FAQ
What's the difference between STL and OBJ?
STL stores only geometry (triangle mesh). OBJ supports textures, materials, and vertex colours. For 3D printing, STL is standard. For rendering and animation, OBJ is more useful.
How do I view an STL file?
Windows 3D Viewer (built-in on Windows 10/11) opens STL files. On any platform, use the free online viewer at viewstl.com, or open in Blender (free) or any slicer software like Cura.
What's the difference between STL and 3MF?
3MF is the modern replacement — it supports colour, materials, multiple objects, and metadata in a smaller file. STL is simpler and universally supported. Most slicers accept both, but 3MF is technically superior.
Related formats