glTF to STL Converter
FileFlip converts glTF to STL entirely inside your browser, using Assimp compiled to WebAssembly. The file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. That means no file-size limit, no queue and no account.
How do I convert a glTF file to STL?#
- Drop your glTF file onto the converter at the top of this page, or click it to pick one from your computer. You can add as many as you like.
- Leave the target set to STL and the conversion starts on its own. FileFlip downloads 11.2 MB of WebAssembly the first time and nothing after that, then runs Assimp on your own machine.
- Save the STL file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting glTF to STL lose quality?#
Not in the sense of pixels or samples. Converting glTF to STL rebuilds the file in STL's own model rather than re-encoding it, so everything STL can represent comes through exactly and anything it cannot has to be dropped. Expect the geometry to be exact, and anything the target has no place for, such as a rig, to be left behind.
Is it safe to convert glTF files online?#
Yes, because nothing is uploaded. FileFlip converts glTF files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What glTF to STL actually does to the file#
Converting glTF to STL runs on Assimp, downloads 11.2 MB of WebAssembly the first time and nothing after that, rebuilds the file in the target's own model, and drops materials, textures and skeleton and animation.
| Engine | Assimp |
|---|---|
| Conversion path | One step: glTF → STL |
| Downloaded to your browser | 11.2 MB, once, then cached by your browser |
| Quality | Rebuilt in the target's model |
| You get back | One file |
| Where it runs | In a background worker, so the page stays responsive |
What survives the conversion
| What is in the file | This conversion | Why |
|---|---|---|
| Materials | Dropped | The target format has nowhere to put it. |
| Textures | Dropped | The target format has nowhere to put it. |
| Skeleton and animation | Dropped | The target format has nowhere to put it. |
Worth knowing before you start:
- the target stores triangles and nothing else, so materials, colours, and texture coordinates have nowhere to go
- if the source carries a skeleton or animation, this target has no place to store it
What is a glTF file?#
A glTF file is a JSON scene description, developed by the Khronos Group and first released in 2015, that lists a model's meshes, PBR materials, animations and scene hierarchy while its binary geometry and textures sit alongside it in separate buffer and image files.
Use glTF's JSON form when a pipeline needs to inspect or hand-edit the scene structure directly, since it's plain, indexed JSON.
Convert glTF to GLB when the model needs to travel or load as a single file instead of a folder of JSON, buffers and textures.
What is an STL file?#
An STL file is a triangle mesh created by 3D Systems in 1987 for its stereolithography 3D printers, storing nothing but a flat list of triangle facets and their normals, with no colour, material or unit of measurement attached.
Use STL when the only destination is a 3D printer's slicer, which is all the format was designed to feed.
Convert STL to 3MF when colour, material or unit information needs to travel with the geometry, since STL has nowhere to put any of it.
glTF to STL questions people ask#
What's the difference between glTF and GLB?
glTF is a JSON text file that references its geometry buffers and textures as separate files, while GLB packs that same JSON, the buffers and the textures into a single binary file. Both describe the identical data model; GLB just bundles everything one file needs to travel as one upload.
Why does my glTF file come with extra .bin and image files?
A .gltf file is only the JSON description of a scene, meshes, materials and animations; the actual vertex data lives in one or more .bin buffer files and textures are separate image files that the JSON references by path. Losing any of those files leaves the model with missing geometry or textures, which is why glTF exports usually come as a folder or ZIP rather than a single file.
Is glTF free to use?
Yes, glTF is a royalty-free open standard published by the Khronos Group, with no licensing fee to implement a reader or writer for it. It became an ISO standard (ISO/IEC 12113:2022) in 2022, which is part of why so many engines and viewers support it.
Can glTF store animation?
Yes, glTF's core specification includes keyframed animation and skeletal skinning alongside meshes and materials, which is part of why it replaced COLLADA as the standard for delivering animated 3D content over the web.