STL to OFF Converter
Convert an STL to a plain OFF vertex and triangle face list. Both formats are geometry-only, so nothing is lost. Runs in your browser.
Drag & drop your STL file here
or click to browse
Supported Formats
Format Information
Source Format
STL.stl
STL (Stereolithography)
STL is an additive-manufacturing format from the 1990s: a flat list of triangles and nothing else. It has no concept of a scene, a material or a texture, which is why it is the lingua franca of 3D printing and also its most lossy interchange format.
What it carries: Triangle positions and, optionally, one facet normal per triangle. No UVs, no vertex colours, no materials, no node hierarchy, no animation.
Open a STL file in the viewerTarget Format
OFF.off
OFF (Object File Format)
OFF is a minimal, human-readable geometry format from the Geomview project: a header line, a count line, then a list of vertex positions and a list of polygon vertex lists. There is deliberately nothing else in the specification.
What it carries: Vertex positions and face index lists, written out as triangles. No normals, no colours, no UVs, no materials, no textures and no animation.
Open a OFF file in the viewerAbout this conversion
The simplest possible geometry export. The triangles are written as a plain OFF vertex and face list — the same shape, in the format a geometry kernel is most likely to read without complaint.
Why convert STL to OFF
- Feed a printer-ready STL into a geometry kernel, simulation tool or custom parser that only accepts OFF.
- Strip an STL down to a tiny, human-readable surface description for a regression test.
- Compare two shapes as plain text, because an OFF diff shows exactly which vertex or face moved.
What happens during the conversion
Geometry
The triangle list is written with node transforms baked into the positions, then the generated OFF is parsed back and its vertex and face counts are verified.
Materials and textures
None. OFF has no material, texture, colour, UV or normal field, so the export is surface geometry only.
Common use cases
- Getting a printer mesh into a geometry kernel or simulation tool that reads OFF.
- Stripping a print part down to pure shape for a renderer or a regression test.
- Turning an STL into a readable text file, so a shape change shows up plainly in a diff.
Limitations of this conversion
- Normals are discarded: STL stores a facet normal per triangle and the OFF writer does not write them, so shading has to be re-derived from the faces. UVs, vertex colours, materials and textures are dropped as well — the source has none of those, and OFF has nowhere to put them.
- Everything is merged into a single mesh.
- Without material data the shape renders flat and untextured in any viewer or slicer preview.
How to convert STL to OFF
Three steps in the browser. Nothing is uploaded to a server, so an unwieldy file is limited only by your own device's memory.
Upload your .stl
Binary and ASCII STL are both supported, and the file's facet normals are read before the package is written.
Convert to OFF
The STL's triangles are written as a vertex and face list that is parsed back and counted before download.
Use the .off in your geometry tool
Vertices and faces only. The STL's facet normals are not written into the file, and there are no texture coordinates either.
Related tools and formats
Other conversions from this format
Check the file in a viewer
Frequently Asked Questions
Questions people ask when turning STL files into OFF.
Looking for a different direction? See every supported conversion.