Format Guide
The universal 3D printing format — simple triangle meshes readable by every slicer, CNC system, and mesh tool.
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| Extension | .stl |
|---|---|
| Full name | STereoLithography / Standard Triangle Language |
| Geometry type | Triangle mesh (facets) |
| Variants | ASCII, Binary |
| Open standard | Yes |
| Supports color | No (binary variant has unofficial color extensions) |
| Supports assemblies | No |
| Supports materials | No |
STL (STereoLithography) was developed by 3D Systems in 1987. It represents a 3D surface as a collection of triangular facets — each triangle defined by three vertices and a normal vector. STL comes in two variants: ASCII (human-readable text, larger files) and binary (5–10× smaller). STL stores no color, material, texture, unit, or assembly information — just raw geometry. Despite these limitations, it remains the most universally understood 3D printing format. Every slicer software (PrusaSlicer, Cura, Bambu Studio, Chitubox) accepts STL.
STL is the default export format for 3D printing. All FDM, SLA, SLS, and resin printers accept STL files. The mesh must be watertight (no holes or non-manifold edges) for slicing to work correctly.
Many CAM systems (Mastercam, Fusion 360 CAM, HSMWorks) accept STL as input for generating machining toolpaths from 3D geometry.
Engineers export design drafts as STL for quick desktop printing to check form and fit before committing to expensive CNC or injection molding runs.
Every slicer (PrusaSlicer, Cura, Bambu Studio), all major CAD systems (SolidWorks, Fusion 360, FreeCAD), and all CAM packages. The most universally readable 3D format.
Commonly converted from STEP or IGES (for 3D printing), to 3MF (for better metadata support and multi-material printing), to OBJ (for rendering), or to PLY (for scan data).
STL is the universal target for 3D printing. Turning a CAD model into a printable STL takes three steps.
Load your model
Drag a STEP, OBJ, IGES or other 3D file into 3D CAD Converter, or point the CLI at a whole folder.
Choose STL and set quality
Pick STL as the output format and set the tessellation level. A finer value follows curved surfaces more closely; a coarser value keeps the file small.
Convert
Export to a watertight STL ready to slice. Choose binary STL for a much smaller file, or ASCII when you need a readable text file.
Prefer the command line? These examples convert to STL:
Lower the tessellation value for smoother prints, or raise it for smaller files and faster slicing.
Almost every 3D printer and slicer on the market reads STL. Because it stores only a simple triangle mesh, with no color, units or assembly data, it is small, portable and supported everywhere, which is exactly why it became the default exchange format for 3D printing.
When you need color, multiple materials or named parts, a richer mesh format is a better fit. Compare STL with 3MF, OBJ.
Want a step-by-step walkthrough? Read how to convert STEP to STL or how to batch convert STL for 3D printing
A printable STL must be a closed, manifold surface. Models built from open surfaces can export with holes or flipped normals. 3D CAD Converter can repair common defects during conversion so the result slices cleanly.
STL carries no color, material or unit information, so a model may look correct but import at the wrong scale. Set the units on conversion, and use 3MF or OBJ instead when you need color and metadata.
ASCII STL is human-readable but can be several times larger than the same model in binary STL. Use binary for large meshes and faster transfers; use ASCII only when you need to inspect the file as text.
A .stl file (STereoLithography, also called Standard Triangle Language) describes a 3D model as a mesh of triangular facets. It stores only surface geometry, with no color, units or materials, which makes it the universal input format for 3D printing slicers. STL comes in a readable ASCII variant and a smaller binary variant.
Open the STEP file in 3D CAD Converter and export to STL, or run cadconvert convert -i part.step -o part.stl from the CLI. The solid STEP geometry is tessellated into triangles; use the tessellation setting to control mesh accuracy and file size, and add --binary for a smaller binary STL.
Yes. You do not need Blender to view or convert STL files. 3D CAD Converter opens STL directly and re-exports it to OBJ, 3MF, glTF and more, and any slicer such as Cura or PrusaSlicer loads STL for printing. Blender is only needed if you want to edit the mesh itself.
A printable STL should be watertight (manifold) with no holes, flipped normals or loose edges. Meshes exported from CAD solids are usually watertight, but models built from open surfaces may not be. 3D CAD Converter can repair common mesh defects during conversion so the STL slices cleanly.