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.
What opens 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
Open a .3mf file step by step
- Confirm the file really is a .3mf. Drop it into the WhatFileType identifier, which reads its signature in your browser without uploading anything.
- On Windows, open it with Cura or PrusaSlicer.
- On Mac, use Cura or PrusaSlicer.
- On Linux, try Cura or PrusaSlicer.
- Still stuck? Convert the .3mf to STL, which opens more widely.
Why can't I open my .3mf file?
Almost always because no installed app understands 3MF. Install one of the apps above, or convert the file to a format your existing software already reads. If double-clicking opens the wrong program instead of nothing at all, the file association is set to the wrong app rather than the file being broken.
The other possibility is that the file is not really a .3mf at all. Drop it into the file identifier to check it by its bytes instead of its name. Nothing is uploaded.
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.
What is the .3mf file signature (magic bytes)?
A .3mf file starts with the hex bytes 50 4B 03 04, which read as PK.. in ASCII. Programs identify 3MF by those bytes, not by the filename, so a renamed file still gives itself away.
These are the documented signatures for 3MF. For a full breakdown, see the ZIP file signature page.
| Hex signature | Offset | ASCII | Note |
|---|---|---|---|
| 50 4B 03 04 | 0 | PK.. | 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
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