3MF files, and how to convert them
3MF was written to replace STL, and on the merits it does. It records its units, keeps several objects apart, carries colour, and is usually a smaller file. It is also what PrusaSlicer, OrcaSlicer and Bambu Studio save their projects as, which is how most people end up with one.
.3mf · model/3mf
3MF conversions that work today
Convert a 3MF file into something else
Make a 3MF file from something else
Things to do with a 3MF file
- Gridfinity generatorBins and baseplates, any size, built in the browser
- Repair an STL that will not sliceClose the holes and separate the bad edges so a slicer accepts it
- Reduce the size of an STL fileFewer triangles, the same shape, a much smaller file
- Check whether an STL is ready to printFind out what is wrong with a model before you print it
- 3D printing cost calculatorThe real cost of a print, and whether to print it or order it
3MF guides
What 3MF fixes
It records the unit. A 3MF says whether it means millimetres, centimetres, inches, feet, metres or microns, so the model arrives at the size it left at. This one fact removes the most common failure in 3D printing file handling.
It keeps objects separate. Five parts arranged on a plate stay five named parts, each with its own placement, instead of merging into one lump of triangles.
It carries colour, per triangle, through colour groups and materials. And because the file is XML inside a ZIP, it compresses well — a 3MF is frequently half the size of the same model as a binary STL.
Slicer project files are 3MF files
When PrusaSlicer, OrcaSlicer or Bambu Studio saves a project, it writes a 3MF with extra parts inside the archive: your print settings, the plate layout, modifier meshes, per-object settings and a thumbnail. The model itself is still a standard 3MF part inside it.
That means a project file opens here and converts like any other 3MF. You get the geometry. The print settings are not geometry and cannot be carried into an STL or an OBJ, so they are dropped — which is fine if you wanted the model, and worth knowing if you wanted the settings.
If you need the settings, keep the original 3MF. Converting it is a one-way trip.
When STL is still the right answer
When you are sending a file to a print service, a customer, or an older machine, and cannot ask what their software reads. STL is refused by nothing.
Also when the receiving end is a tool that claims 3MF support but implements only part of it. Support has improved a great deal, but a plain STL still has fewer ways to go wrong when you will not be there to fix it.
What 3MF cannot store
- Exact curved surfaces — like STL, it stores triangles
- Animation or rigging
- Your slicer settings, once converted to any other format
3MF in detail
| Property | 3MF.3mf |
|---|---|
| File contents | A ZIP archive holding XML. The model itself is one XML part inside it. |
| Geometry | Triangles, with a build platform and placement for each object. |
| Units | Recorded in the file. Millimetre, centimetre, inch, foot, metre or micron. |
| Colour and texture | Colour groups and materials per triangle, and textures in later extensions. |
| Separate objects | Several named objects, each placed on the build plate with its own transform. |
| Published by | The 3MF Consortium, 2015, explicitly to replace STL. |
| Written by | PrusaSlicer, OrcaSlicer, Bambu Studio, Cura, Fusion 360 and Windows itself. |
Questions
- Can I convert a Bambu Studio or PrusaSlicer project file?
- Yes. Those project files are 3MF archives with extra parts inside, and the model part is standard. Drop one in and you get the geometry out. The print settings cannot travel into another format and are dropped.
- Is 3MF better than STL?
- Technically, in every respect: units, colour, separate objects, smaller files. The one thing STL has is that nothing refuses it. Use 3MF where you control both ends, STL where you do not.
- Does colour survive when I convert a 3MF?
- To OBJ and GLB, yes, as materials. To STL, PLY and OFF, no — none of those has anywhere to put it. The converter page for each pair says which before you start.
- Why does my 3MF have several objects when the STL had one?
- Because 3MF can hold several and STL cannot. If the original model was an assembly that STL had merged into one body, converting to 3MF does not separate it again — the information was lost at the STL stage and cannot be recovered.