Free online 3MF viewer
Drop a .3mf to see the objects packed inside it, their colours, and their size in the unit the file itself declares. It is read in your browser and never uploaded.
How to open a 3MF file
- Drop the .3mf on the viewer or click to choose it. A 3MF is a zip package; do not unpack it, the viewer reads it whole.
- Check the panel: how many objects the package holds, the unit written in the file (millimetre unless it says otherwise) and the bounding box in that unit — a size you can compare with your printer's bed.
- Orbit to inspect the parts. Wireframe shows the triangulation; the Z-up / Y-up switch is there for files exported from tools that do not follow the format's Z-up rule.
Why 3MF exists, and what it carries that STL does not
3MF was published in 2015 by a consortium of printer and CAD companies to replace STL for 3D printing. Inside the zip is an XML document that states its unit (micron, millimetre, centimetre, inch, foot or metre), lists meshes with shared vertices, and can give them names, base materials, per-triangle colours and textures. Several objects and several copies of one object fit in a single file, each with its own placement on the build plate.
Slicers also use the package as a project file: Bambu Studio, OrcaSlicer and PrusaSlicer save print settings, supports and plate layouts next to the model. Those are private additions of each slicer. This viewer shows the geometry and its colours, not the print settings.
For avatars there is nothing here: 3MF has no skeleton, no skin weights and no blendshapes. It is a format for making an object, not for animating a character.
What this viewer does not do
It reads the core model, base materials, colour groups and textured materials. It does not draw the slice extension (pre-sliced layers) or beam lattices, and says so when a file contains them. Slicer project files keep each object in its own model file inside the package (the production extension); those are merged into one model before drawing, and the panel says when that was done. Colours painted onto a model in the slicer, print settings, supports and filament assignments are not shown, and nothing is checked for printability.
Frequently asked questions
What units is a 3MF in?
Whatever the file declares, and unlike STL it always has an answer: the unit is an attribute of the model, and when it is absent the specification says millimetre. The panel shows the unit and whether it was written in the file or is the default, and gives the bounding box in that unit.
Is 3MF better than STL?
For printing, yes in every way that matters: it knows its units, shares vertices so files are smaller, keeps several parts and their positions in one file, and can carry colour. STL survives because every tool ever written reads it. If your slicer accepts 3MF, there is no reason to export STL.
Does it open project files from Bambu Studio, OrcaSlicer or PrusaSlicer?
It opens their geometry. Those slicers store each object in its own model file inside the package and reference it from the main one; the viewer merges the pieces into one model before drawing and notes that it did. What it leaves out is everything slicer-specific: painted colours and seams, supports, plate assignments and print settings. If a project opens incomplete, exporting the plate as a plain 3MF from the slicer gives a simpler file.
Does it show multi-colour models?
It shows colour that is stored the standard way: base materials and per-triangle colour groups. Painted multi-material regions made in Bambu Studio or PrusaSlicer are saved as slicer-specific data and are not displayed.
Can I see the print settings or the sliced layers?
No. Settings live in slicer-specific files inside the package, and sliced output is a different file altogether. To look at layers and toolpaths, export the G-code and open it in the G-code viewer.
Is my file uploaded?
No. The package is unzipped and drawn in your browser. Nothing in it is sent to a server.
Can a 3MF become a VRM avatar?
No. A VRM needs a humanoid skeleton and facial blendshapes; 3MF cannot store either. A printable figurine and an avatar of the same character are two different models.
From model to print
Once the part is sliced, the G-code viewer shows the toolpath layer by layer. Still holding an old STL? It opens on its own page, with the caveat that it has no units to report.