What is a .3mf file?
3D Manufacturing Format · 3D model · 3MF Consortium · 2015
3MF is a modern 3D printing format built to fix STL's limits. Unlike STL it carries colour, materials, textures, units and multiple objects in one file, and it is a zipped package of XML, so it is compact and unambiguous.
What is a .3mf file used for?
Where an STL is only a bare mesh of triangles, a 3MF records a complete, print-ready model: real-world units, colours, materials, textures and several parts in a single file, validated to be watertight.
Under the hood it is an OPC package, the same zipped-XML approach as DOCX, which keeps it small and machine-readable.
It is backed by Microsoft, Autodesk, HP and others, and modern slicers like PrusaSlicer and Cura, plus Windows itself, open it directly.
For older tools that only understand STL, a slicer can export the 3MF back down to STL, losing the extra colour and material information.
How to open a .3mf file
The .3mf format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list.
Windows
- Cura
- PrusaSlicer
- Windows 3D Viewer
- Blender
macOS
- Cura
- PrusaSlicer
- Blender
Linux
- Cura
- PrusaSlicer
- Blender
Web
- Online 3D viewers
How to convert a .3mf file
You can convert a .3mf file to STL, OBJ, GLTF using a conversion tool or the export menu of an app that opens it.
.3mf file signature (magic bytes)
Programs recognise a .3mf file by the bytes at the start of the file, not by its name. These are the signatures for 3MF. For a full breakdown, see the 3MF file signature page.
| Hex signature | Offset | Note |
|---|---|---|
| 50 4B 03 04 | 0 | ZIP header; 3MF is an OPC package of XML, like DOCX |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .3mf file?
3MF is a modern 3D printing format built to fix STL's limits. Unlike STL it carries colour, materials, textures, units and multiple objects in one file, and it is a zipped package of XML, so it is compact and unambiguous.
Should I use 3MF or STL?
Use 3MF when your slicer supports it: it keeps units, colour, materials and multiple parts, and avoids STL's rounding and watertightness problems. STL is still the safest choice for older tools that do not read 3MF.
How do I open a 3MF file?
Open it in a 3D printing slicer like PrusaSlicer or Cura, the Windows 3D Viewer, or Blender. Since it is a ZIP underneath, you can also rename it to .zip to inspect the XML and textures inside.
Related formats
Sources
Details on this page were checked against authoritative references: