MDL to STL Converter
FileFlip converts MDL 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 an MDL file to STL?#
- Drop your MDL 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 MDL to STL lose quality?#
Not in the sense of pixels or samples. Converting MDL 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 MDL files online?#
Yes, because nothing is uploaded. FileFlip converts MDL 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 MDL to STL actually does to the file#
Converting MDL 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: MDL → 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 an MDL file?#
An MDL file is most often id Software's original Quake model, a small vertex-animated mesh with a single texture, or an unrelated 3D GameStudio model that happens to share the same extension, so the extension alone never says which format a given file actually is.
Use MDL only when working directly inside the specific pipeline that produced it, whether that's Quake modding or 3D GameStudio, since the two formats aren't interchangeable despite the shared extension.
Convert an MDL file to a modern interchange format once its origin (Quake, 3D GameStudio, or something else entirely) is confirmed, since converting the wrong format's loader against it will simply fail.
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.
MDL to STL questions people ask#
What is an MDL file?
Most commonly, an MDL file is id Software's original Quake model format from 1996, a small vertex-animated mesh with one texture, identified internally by the magic bytes IDPO. The same extension is also used by 3D GameStudio's unrelated model format and by other software entirely, so the name alone doesn't guarantee which one you have.
Is every MDL file a Quake model?
No. 3D GameStudio's model format uses the same .mdl extension across several incompatible versions, and Valve's studiomdl compiler also writes its compiled GoldSrc and Source engine models as .mdl. None of these read as a Quake model, so the file has to be checked before assuming which format it is.
What software still opens Quake's MDL format?
Modern Quake source ports like Quakespasm load the original MDL models directly, and tools such as Noesis, MilkShape 3D and QuArK read them for inspection or conversion outside the game.
What is an STL file used for?
An STL file is the standard input for 3D printer slicing software, storing a model's surface as a list of triangles with nothing else attached. Slicers use it to work out where to lay down material layer by layer.