Free STL (.stl) to 3MF (.3mf) converter — running entirely in your browser. No upload, no signup, no file limits: your files never leave your device.
STEP · IGES · BREP · STL · OBJ · PLY · GLB · glTF · 3MF · COLLADA · AMF · FBX · 3DS · OFF
STL is the de-facto standard for 3D printing. It describes a model purely as a mesh of triangles — no color, no units, no assembly structure — which makes it simple, universally supported, and the required input for virtually every slicer, from PrusaSlicer and Cura to resin-printer tools.
3MF is the modern replacement for STL, backed by the 3MF Consortium (Microsoft, HP, Autodesk, Prusa and others). It stores watertight meshes together with units, colors, materials and print settings in one ZIP-based file, and current slicers increasingly prefer it over STL.
| STL | 3MF | |
|---|---|---|
| Geometry | Triangle mesh | Watertight triangle mesh |
| Units | No — unitless numbers | Yes, required by spec |
| Colors & materials | No | Colors & materials |
| Animations | No | No |
| Typical use | 3D printing | Modern 3D printing |
Yes — free with no accounts, no watermarks and no file-size limits. Conversion runs on your own machine, so there are no server costs behind it.
No. The converter runs entirely in your browser using WebAssembly. Your .stl file never leaves your device, which makes it safe for confidential designs.
Yes — parts and assembly hierarchy are preserved where 3MF supports them, and you can optionally merge everything into a single mesh during conversion.
Yes. Every converted model opens in the built-in 3D viewer with an assembly tree, display modes and section views, so you can inspect the result first.
STL already contains only unitless triangles, with no part names, colors or design history for a converter to preserve. The 3MF writer keeps model units, part names and one base color per mesh, but it does not write textures, advanced materials or print settings.
Which file format should you actually print from? A practical ranking of STL, OBJ, 3MF and AMF for FDM and resin printing, with free conversion tools.
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