3MF to STL Converter
FileFlip converts 3MF 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 3MF file to STL?#
- Drop your 3MF 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 3MF to STL lose quality?#
Not in the sense of pixels or samples. Converting 3MF 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 3MF files online?#
Yes, because nothing is uploaded. FileFlip converts 3MF 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 3MF to STL actually does to the file#
Converting 3MF 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: 3MF → 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 3MF file?#
A 3MF file is a ZIP archive of XML documents, published by the 3MF Consortium in 2015 as 3D printing's replacement for STL, adding the colour, material, unit and multi-object placement data STL never had.
Use 3MF over STL whenever colour, material or multiple positioned objects need to travel with the geometry to the printer.
Convert 3MF to STL only when the destination software is old enough to not support 3MF at all.
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.
3MF to STL questions people ask#
What is a 3MF file?
A 3MF file is a 3D printing format, a ZIP archive of XML, published by the 3MF Consortium in 2015 to replace STL. It adds colour, material, real-world units and multiple objects with their placement on the build plate, none of which STL can store.
Is 3MF better than STL?
3MF can carry colour, material, units and multiple positioned objects in one file, all of which STL simply has no fields for. STL still has broader support since it's decades older, so the better choice depends on whether the printer and slicer being used actually support 3MF.
Does my 3D printer support 3MF?
Most current slicers, including PrusaSlicer, Cura and Bambu Studio, read 3MF natively and it's become the default project format for several of them. Older or budget slicer software may still expect STL, so it's worth checking a specific printer's software before relying on 3MF alone.
Can I open a 3MF file with a ZIP tool?
Yes, a 3MF file is literally a ZIP archive containing XML documents, so any standard archive utility can open it and show the files inside. That doesn't render the model, but it does let you inspect the raw geometry and metadata directly.