FILE FORMAT GUIDE
What Is a 3MF File?
The 3D Manufacturing Format: a ZIP archive that carries the mesh plus the units, colors, and print settings a modern slicer needs.
A ZIP archive with a 3D model inside
A 3MF file is the 3D Manufacturing Format — an open container so a printer, or a slicer talking to one, receives geometry together with the metadata that geometry actually needs. The container is a ZIP archive. Inside it lives XML, typically at 3D/3dmodel.model, that describes one or more objects, their units, optional color and material assignments, and a scene graph. You can prove this yourself: rename a .3mf to .zip, open it, and you will see the same folder layout the specification requires. That is not a vendor quirk; it is the format.
The 3MF Consortium created and maintains it. Members and contributors include Microsoft, Autodesk, HP, Prusa Research, Ultimaker, and other CAD, printer, and software vendors that needed a successor to STL. The specification is published on GitHub. The work was never another mesh format for its own sake. It was to stop shipping a bag of triangles that forgets whether those numbers are millimeters or inches, whether two parts on the plate are separate objects, and which filament goes where.
Because the archive is extensible, slicers adopted 3MF as their project format. Bambu Studio, PrusaSlicer, Orca Slicer, and Cura all save plates, supports, modifiers, and per-object print settings into a 3MF. A download from MakerWorld or Printables is often a full project, not a naked mesh. Opening it in the originating slicer restores the plate. Treating it as geometry-only, or converting it, does not.
3MF vs STL
STL is a list of triangles and nothing else. 3MF is a package that can hold those triangles plus everything around them. Use the table as a map, not a verdict — you will keep both formats.
| 3MF | STL | |
|---|---|---|
| What it is | ZIP archive of XML (typically 3D/3dmodel.model) | Raw triangle list |
| Units | Stored in the file (mm by default) | None — importers guess, usually mm |
| Color / materials | Yes | No |
| Multiple objects | Named objects with transforms | One triangle soup |
| Slicer project data | Used by Bambu Studio, PrusaSlicer, Orca, Cura | Geometry only |
| Typical share | Complete print project | Maximum compatibility |
Keep 3MF when you still intend to print the file as a project. Export or convert to STL when the next program in the chain only reads triangles. For a closer look at the older format, see what an STL file is.
When to convert 3MF to STL
Convert when the next tool does not speak 3MF. Older mesh repairers, many CAD importers, some print services, and a long tail of game-engine and mold-making pipelines still accept STL only. You also convert when you want the geometry and nothing else: a repair pass, a boolean in a CAD package that imports STL, or a share to someone whose software predates 3MF.
Use the 3MF to STL converter on this site for that extraction. Conversion runs in the browser; the file is not uploaded. Geometry is written out as binary STL with object transforms applied. Print settings, colors, and plate metadata stay behind because STL has nowhere to put them.
If you only need to inspect a 3MF — triangle count, dimensions, whether the objects look right — open it in the viewer on the home page. Parsing happens in your tab; nothing is uploaded. You do not need Bambu Studio, PrusaSlicer, or Cura installed to take a look.
FAQ
Is a 3MF file really a ZIP archive?+
Yes. The .3mf extension names a ZIP container whose payload is XML, plus optional textures and thumbnails. The core model typically sits at 3D/3dmodel.model. Renaming the file to .zip and unzipping it is a supported way to inspect the contents — it is how the format is defined, not a hack.
Does converting 3MF to STL lose my print settings?+
Yes. STL stores geometry only: a list of triangles. Layer height, supports, plate layout, colors, materials, and per-object metadata are dropped. The mesh itself is kept, with object positions and orientations applied. If you still need the project, share the 3MF.
Can I open a 3MF file without installing a slicer?+
Yes. The viewer on this site opens 3MF in the browser and shows a preview, triangle count, and dimensions. Parsing runs in your tab; nothing is uploaded. You do not need Bambu Studio, PrusaSlicer, Orca, or Cura installed to take a look.
Should I share 3MF or STL?+
Share 3MF when the recipient should print the project as you set it up — plate, settings, colors, and all. Share STL when you need maximum compatibility: older tools, mesh repair, and CAD importers that still only accept triangles.
Who maintains the 3MF format?+
The 3MF Consortium, an industry group whose members include Microsoft, Autodesk, HP, Prusa Research, Ultimaker, and other CAD and printer vendors. The core specification is published on GitHub; slicer vendors extend it with their own namespaces for project data.