Design & 3D · .stl
What Is an STL File?
A .stl file is a 3D model file used for 3D printing.
- Extension
- .stl
- Full name
- Stereolithography 3D model
- Type
- Design & 3D
- MIME type
- model/stl
- Developed by
- 3D Systems (1987)
Free STL Tools
These run in your browser. Your STL files are never uploaded.
About STL Files
STL describes the surface of a 3D object as a mesh of triangles, without colour or texture. It's the standard format for 3D printing: you download or design a model as STL, then a slicer program turns it into instructions for your printer. STL files can be text or binary; binary ones are much smaller. Newer formats like 3MF add colour and units, but STL is still the most widely supported.
How to Open an STL File
- Windows
- Open it in 3D Viewer, or in a slicer such as Cura, PrusaSlicer or Bambu Studio.
- Mac
- Preview and Quick Look show STL models. Use a slicer to print.
- Any device
- Many 3D model sites preview STL in the browser.
STL File Questions
How do I 3D print an STL file?
Open it in a slicer such as Cura or PrusaSlicer, choose your printer and settings, and export G-code.
Why is my STL the wrong size?
STL has no units. A model designed in inches may appear 25 times too small if the slicer assumes millimetres.