Convert STL to glTF
Free STL to glTF converter that runs in your browser. See real dimensions before you download.
How to convert STL to glTF
- Drop your STL file onto the converter — it opens in your browser, nothing is uploaded.
- Check the preview and the dimensions in mm; fix units or the up axis in “Units & orientation” if the size or orientation looks wrong.
- Choose glTF as the output and click Convert. Several files download as one ZIP.
What carries over from STL to glTF
| STL | glTF | Result | |
|---|---|---|---|
| Colour / materials | No | Yes | — |
| Textures | No | Yes | — |
| Units stored in file | No | Yes | Written as mm → metres |
| Separate parts | No | Yes | — |
| Usual up axis | Z | Y | Rotated (switchable) |
About STL files
STL was created by 3D Systems in the late 1980s for its stereolithography machines, and it became the default exchange format for 3D printing. A file describes a surface as a list of triangles, each with three vertices and a facet normal. That is all it contains. There is no header field for units, no colour, no texture and no notion of separate parts. Two flavours exist: ASCII, which is readable text but large, and binary, which spends exactly 50 bytes per triangle after an 80-byte header and a 4-byte triangle count. Binary is what almost every modern tool writes. Because the format is so small and so old, every slicer, CAD package and mesh editor can read it, which is why hobbyists still download most printable models as STL from sites like Printables and Thingiverse.
About glTF files
glTF was developed by the Khronos Group, the body behind OpenGL and Vulkan, and version 2.0 was released in 2017 and later adopted as ISO/IEC 12113. The design goal was a lean transmission format that engines can load without heavy processing. In its text form, a .gltf file is JSON that lists scenes, nodes, meshes, materials, animations and accessors, and it points to external .bin buffers and image files, though buffers can also be embedded as base64 data. The same content packed into one file is called GLB. Because the JSON is readable, glTF is popular for tooling, pipelines and debugging, and for projects that want to diff or hand-edit assets. It uses metres, a right-handed coordinate system and +Y up, and its physically based materials are supported by most web and game engines.
3D printing notes
STL is still the safest file to hand to a slicer. Bambu Studio, PrusaSlicer, OrcaSlicer, Cura and the resin tools Chitubox and Lychee all import it, and they all treat the numbers as millimetres. The usual problems are scale (a model exported from a metre-based tool arrives 1000 times too small) and meshes that are not watertight, which makes slicers fill or skip regions. MeshShift shows the real dimensions before you convert and can scale from metres automatically. Its print check lists holes, non-manifold edges and flipped normals, and one click rebuilds a closed solid at the same size. If you need colours or several plates in one file, use 3MF instead.
Frequently asked questions
Is this STL to glTF converter free and private?
Yes. The conversion runs in your browser with JavaScript and WebAssembly, so your STL file is never uploaded to a server. There is no sign-up, no watermark and no daily limit; very large files are limited only by your device's memory.
Does an STL file contain units or colour?
No. The STL standard has no field for units and none for colour, so slicers assume millimetres and print in whatever filament you choose. A few programs squeeze colour into the two spare bytes of each binary triangle, but those files are non-standard and many slicers ignore the data.
Should I use glTF or GLB?
Choose GLB when you want to share, upload or ship one file with textures inside. Choose glTF when you need to read or edit the JSON, keep textures separate, or let a version control system show changes. Both are the same standard and convert losslessly.