3MF is the modern replacement for STL, backed by the 3MF Consortium (Microsoft, HP, Autodesk, Prusa and others). It stores watertight meshes together with units, colors, materials and print settings in one ZIP-based file, and current slicers increasingly prefer it over STL.
PrusaSlicer, Bambu Studio, OrcaSlicer, Cura and Windows 3D Builder all write 3MF, and Fusion 360 and SolidWorks export it for printing. It is the format that fixed STL’s missing units, colors and materials, backed by the 3MF Consortium.
Best for: Modern 3D-printing workflows that need more than bare triangles. There is a fuller write-up on the 3MF format reference page.
Every format on this site also gets the same viewport tools: orbit, pan and zoom with fit-to-view, isometric and the six standard views, a perspective/orthographic toggle, shaded, shaded-with-edges, wireframe and X-ray display, hide-selected, and a PNG screenshot of the current view. The same controls are on the general 3D and CAD viewer, which accepts every importable format at once.
Worth knowing before you rely on it. A viewer that overstates what it can read wastes more of your time than one that is specific about its limits.
| 3MF files | |
|---|---|
| Extensions | .3mf |
| Geometry | Watertight triangle mesh |
| Units | Yes, required by spec |
| Colors & materials | Colors & materials |
| Animations | No |
| Typical use | Modern 3D printing |
3MF declares its unit inside the model file, but the readouts show raw coordinates with a millimetre label. That matches the format’s millimetre default, so it is usually right.
3MF is both readable and writable here, so it is often the target rather than the source. From a 3MF the usual move is out to STL for an older toolchain. The converter runs on the same local pipeline as this viewer, so a conversion is just as private as a preview: 3MF to STL is the usual choice.
It opens the geometry inside it: objects, build items and colors all display. The slicer-specific project data — profiles, supports, paint, per-object modifiers — is not read, so treat this as a model viewer rather than a project viewer.
No. The ZIP container is unpacked and its XML parsed inside your browser tab. Because that parsing needs DOMParser it runs on the main thread rather than a worker, but it still never leaves your device.
More so than for STL. 3MF requires watertight meshes, so the signed-volume calculation has a closed surface to work with. It is still geometry-only — it knows nothing about infill density or walls.
3MF, if the tools in your chain read it. It stores units, colors and materials that STL simply cannot, and it is a smaller file. Keep STL only for the older slicers and services that still require it.
Geometry: watertight triangle mesh. Units: yes, required by spec. Colors and materials: colors & materials. Animations: no. Of that, the viewer draws geometry and flat base colors; texture maps and animation are never displayed. 3MF declares its unit inside the model file, but the readouts show raw coordinates with a millimetre label. That matches the format’s millimetre default, so it is usually right.
Read the 3MF format reference for the format itself, open the general 3D and CAD viewer if you have several formats to look at, or start from the 3D and CAD converter.
If the model is heavier than it needs to be, the mesh simplifier reads .3mf directly, decimates it in your browser and previews the result before you export. If the file is headed for a 3D printer, the G-code viewer shows the sliced toolpath layer by layer once your slicer has run.
3MF fixes almost everything wrong with STL — units, colors, watertightness, file size. A practical comparison, plus free tools to convert STL to 3MF.
Which file format should you actually print from? A practical ranking of STL, OBJ, 3MF and AMF for FDM and resin printing, with free conversion tools.