3MF Viewer — Open 3MF Files Online
Open 3MF print files with colour and materials intact — the modern replacement for STL.
Your 3MF file is read and rendered entirely by your own browser. It is never uploaded to A23D, never stored, and never seen by anyone but you.
How to open an 3MF file
No account, no plugin, no upload. Three steps and your model is on screen.
Drop in your file
Drag the .3mf onto the viewer, or click to browse. If the model references separate material or texture files, drop the whole folder or a .zip so everything resolves.
Inspect the scene
Orbit, pan and zoom to look around. The inspector lists every mesh in the hierarchy with its triangle count, and reports the bounding box so you can sanity-check scale.
Convert or capture
Save a PNG of the viewport, or download the model converted to GLB, OBJ, STL, PLY or USDZ — all without the file leaving your browser.
What is a 3MF file?
3MF, the 3D Manufacturing Format, was published in 2015 by the 3MF Consortium — a group including Microsoft, Autodesk, Dassault, HP, Shapeways and Ultimaker. It was created specifically to replace STL, whose limitations had become a genuine obstacle to colour and multi-material printing.
A .3mf file is a ZIP archive containing XML. Inside sits a model part describing the geometry, plus optional parts for materials, colours, textures, print tickets and thumbnails. The container approach means a single file carries everything a printer needs, and new capabilities can be added without breaking older readers.
Where STL stores unconnected triangles, 3MF stores a proper indexed mesh with shared vertices. That makes files considerably smaller, removes the numerical noise that causes STL meshes to arrive non-manifold, and lets the format express a watertight solid unambiguously.
Crucially, 3MF declares its unit. The model element states whether measurements are in millimetres, centimetres, inches, feet or microns, so a part arrives at the correct physical size instead of relying on convention. It also supports full object hierarchies, transforms and multiple build items on one plate.
Colour and material support is the other reason to prefer it. 3MF can carry per-object base materials, per-triangle colour groups and full texture mapping — none of which STL can express — which is what makes it the format of choice for full-colour and multi-material printing.
3MF at a glance
- Extension
- .3mf
- Developer
- 3MF Consortium
- First released
- 2015
- Encoding
- ZIP archive of XML
- Unit
- Declared in the file
- Colour
- Supported
- Replaces
- STL
What this viewer supports
- Indexed mesh geometry with shared vertices
- Object hierarchy, transforms and build items
- Base materials and colour groups
- Declared unit honoured for dimensions
- Export to GLB, OBJ, STL, PLY, USDZ
- Print tickets and slicer settings
3MF viewer FAQs
The questions we get asked most about opening 3MF files.
Is my 3MF uploaded anywhere?
No. The archive is unpacked and rendered inside your browser. Print files are frequently unreleased designs, and none of it is sent to A23D or retained.
What is the advantage of 3MF over STL?
3MF stores an indexed mesh rather than loose triangles, so files are smaller and far less prone to arriving non-manifold. It also declares its unit, and supports colour, multiple materials, textures and object hierarchies — none of which STL can represent.
Will my 3MF colours show?
Yes, where the file defines them. 3MF can carry base materials and per-triangle colour groups, and both are read here. If a file was exported as plain geometry it will render in the default grey.
Why does 3MF get the size right when STL does not?
Because 3MF explicitly records its unit — millimetres, inches and so on — in the model element. STL declares nothing, so every program has to assume, which is why parts sometimes arrive 25.4 times too large or too small.
Can I convert 3MF to STL?
Yes. Load the file and use Convert to, then pick STL. Be aware that STL cannot store colour or materials, so that information is discarded in the conversion. Convert to GLB instead if you want to keep it.
Do all slicers support 3MF?
Most modern ones do, including PrusaSlicer, Cura, Bambu Studio and Simplify3D. It is the recommended format for anything involving colour or multiple materials.
More format viewers
All browser-based, all free, nothing uploaded.
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