Free online 3MF viewer
Drop a .3mf as it is: the page reads the package whole, lists its objects and colours, and shows the size in the unit the file declares.
How to open a 3MF
- Drop the .3mf on the page. It is a zip package; do not unpack it, the viewer reads it whole.
- Read the panel: how many objects the package holds, the unit written in the file (millimetre unless it says otherwise) and the box the parts fit in, a size you can compare with your printer bed.
- Orbit to inspect the parts. Wireframe shows the triangulation; the Z-up / Y-up button is for files written by tools that ignored the format's Z-up rule.
Why 3MF over STL
A 3MF carries what STL cannot: a unit, several named objects, per-object or per-triangle colour and materials, and the placement of parts on the bed. The viewer shows those; what it does not read are the slicer-specific extensions a print profile adds, which live beside the model in the package and mean nothing without that slicer.
Limits
A package over 150 MB, or one that unpacks to more than 600 MB or 2,000 files, is refused rather than frozen. Beam lattices and texture-mapped surfaces are drawn plain.
Frequently asked questions
Does a 3MF have anything to do with avatars?
No. It is a print package: geometry and colour for a slicer. A VRM avatar needs a rig and a face, which no print format carries.
Are the colours the real ones?
Where the package assigns a colour or a material to an object or a triangle, yes. Multi-material slicer settings are not read.
Why does it say millimetre?
Because the file does, or because it says nothing: the 3MF specification makes millimetre the default unit.
Can I check printability here?
No. The page shows the geometry; holes and thin walls are a slicer's job.
Is the file uploaded?
No. The package is unzipped and drawn in your browser.
How do I get an STL out of it?
Save the object from your slicer, or convert the mesh here through the OBJ or GLB pairs once it is in one of those formats.
The same part as a mesh
A 3MF is a print package; for a plain mesh, export it from your slicer as STL or OBJ and open it in the STL viewer.