Format at a glance
- Full name
- Stereolithography Mesh
- File extensions
- .stl
- MIME types
- model/stl
- Category
- 3D models
- Compression
- Depends on the contained codec
- Transparency
- Not applicable
- Animation
- Not applicable
- Properties
Suitable tools
What is this format?
STL exists in readable ASCII and more compact binary forms. Each triangle contains three vertices and a normal; shared vertices do not need to be referenced jointly.
A printable mesh should be closed and manifold with correct normals and no self-intersections. The file format itself does not enforce these quality rules.
What is it used for?
- Exchanging models for 3D printing
- Import into Cura, PrusaSlicer and other slicers
- Simple triangulated CAD exports
- Prototypes without material information
Which programs can open it?
- PrusaSlicer, Cura and OrcaSlicer
- Blender and MeshLab
- CAD applications
- 3D-printer and mesh-repair tools
Support across devices and browsers
Blender, MeshLab, CAD software and slicers open STL.
Blender, MeshLab and compatible CAD or printing tools support STL.
Open-source 3D tools and command-line programs process STL.
3D viewers can display STL, usually with fewer editing features.
Compatible 3D viewers and CAD applications import STL.
Browsers require a JavaScript WebGL or WebGPU renderer; LocalFileLab reads only the implemented geometry data.
Advantages
- Very broad 3D-printing support
- Simple structure
- Binary files are compact for pure triangle meshes
Disadvantages
- No defined unit
- No standardized colors, materials or textures
- Curves are only approximated by triangles
Comparison with alternatives
OBJ can reference UVs, normals and materials; STL focuses on plain triangles.
3MF stores units, materials and printing information more explicitly.
PLY can store extra point and face attributes such as color.
LocalFileLab support
STL is recognized as an input. Supported geometry and material references are read locally.
STL is available as a local output; available settings depend on the format.
LocalFileLab can compress STL locally or package it in a supported archive; already compressed content will not necessarily become smaller.
A complete STL preview is not currently available.
Complete preservation of format-specific metadata is not guaranteed.
Related formats
Frequently asked questions
Is STL always measured in millimeters?
No. STL stores no unit. Slicers often assume millimeters, while other programs may expect meters or inches.
Which is better: ASCII or binary STL?
Binary STL is usually much smaller. ASCII is easier to inspect but has no additional standard features.
Why is an STL model not printable?
Holes, non-manifold edges, wrong normals or self-intersections can require repair before slicing.