What is a 3MF file?
3MF, the 3D Manufacturing Format
3MF is what STL should have been. Where STL is bare triangles with no color or units, 3MF is a modern, self-describing format that keeps everything a print needs in one file. Every current slicer reads it, and multi-color and multi-material printing has largely moved to it.
What's inside a 3MF
A .3mf file is a ZIP container of XML. Inside, it describes the meshes, their color and materials, multiple build items (so a whole plate of parts fits in one file), and print metadata. Crucially, it records explicit units, so a 3MF arrives knowing its own real-world size — none of the millimetre-or-inch guesswork STL forces on you.
It's backed by the 3MF Consortium, whose members include Microsoft, Autodesk, HP and Prusa, which is why support is broad and consistent. Bambu Studio, PrusaSlicer, OrcaSlicer and Cura all read and write it.
Model file vs project file
There's a nuance worth knowing: a .3mf saved by a slicer is often a whole project — plate layout, print settings, supports, sometimes G-code — wrapped around the geometry, not just a plain model. Reopen that in the slicer that made it to get everything back; a generic 3MF viewer will show the geometry and color, not the slicer's settings.
The reason 3MF matters now is color. STL simply can't carry it, so any multi-color model — a Bambu AMS print, a multi-material design — needs 3MF (or OBJ) to survive. As slicer support became universal, 3MF became the natural default, with STL kept as the compatibility fallback.
3MF files — FAQ
- 3MF or STL — which is better for printing?
- If your slicer supports 3MF (all current ones do), 3MF is the better file: it keeps units, color and multiple parts in one place, where STL drops all of that. Reach for STL only when a tool or service accepts nothing else.
- How do I open a 3MF file?
- Any modern slicer opens it (Bambu Studio, PrusaSlicer, OrcaSlicer, Cura). To just view the geometry and color without a slicer, use a browser 3MF viewer.
- Does 3MF keep color?
- Yes — 3MF stores color and material per object, which is the main reason it's replacing STL for multi-color and multi-material printing. A multi-color 3MF keeps its color; the same model as STL would print as one solid piece.
- Why doesn't my Bambu/Prusa 3MF project fully open elsewhere?
- A slicer-saved .3mf is usually a whole project — plate layout, settings, supports — wrapped around the model. Other tools show the geometry, not the slicer's settings. Reopen it in the slicer that created it to get the full project back.
- Can I convert a 3MF to STL?
- Yes. If a tool in your chain only accepts STL, flatten the 3MF to geometry with a 3MF-to-STL converter — you'll lose the color and part separation, which is exactly the trade STL forces.
Working with 3MF files
Need a 3D model, not just the file format?
Describe it or drop in a photo — Sculptor generates a 3D model and exports it as 3MF, GLB, STL or OBJ in about a minute.
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