What a 3MF package contains
3MF is published openly by the 3MF Consortium, founded in 2015. A .3mf file is a ZIP package with an XML model at 3D/3dmodel.model. Unlike STL, it names its unit (millimetre by default) and can store color and materials.
The viewer reads the meshes for size, volume and the mesh check. If you slice here, our slicer uses only the values you set in its Slice panel.
Open a 3MF file online in four steps
- Drop the .3mf on the page or press Open File.
- Read X × Y × Z, volume and surface area in Info. Units mm/in switches the display.
- Check the mesh line: watertight yes or no, holes, open edges, flipped triangles.
- Press Convert to save STL, OBJ or another target, or Slice to make G-code.
In the round-trip test, a 20 mm cube went from 3MF to STL and back with the same size, volume and triangle count.
Files the 3MF viewer will not open
Bambu Lab printers normally take .gcode.3mf project files from Bambu Studio. Those packages do not open here. Open the source .3mf instead, or export the plate as a model from the slicer that made it.
A mesh with a million triangles opens in about 5 to 12 seconds. Above roughly 1 to 2 million triangles the tab may run out of memory.
Repair a 3MF and save it back
A 3MF downloaded from a model site can still have open edges or inverted normals, and you only find out when the slicer complains. Edit → Repair welds duplicate vertices, removes degenerate triangles, turns the normals outward and closes simple holes. Its message lists what it fixed and what is still open. Scale, rotate, lay on bed and cut work on the same mesh, with 20 steps of undo.
Convert → 3MF saves the result in millimetres. In the timing tests, writing a 3MF of 1M triangles took about 4 to 5 seconds.
Weight and cost from a .3mf
Info turns the volume into grams for 17 materials, such as ABS at 1.04 g/cm³, PLA at 1.24 and PETG at 1.27. A % solid field accounts for infill. Enter a price per kg and an hourly rate to get a cost, or work it out on the 3D print cost calculator.
Converters for 3MF, both ways
When a tool or a model site asks for STL, 3MF to STL handles that. 3MF to OBJ suits rendering apps, and 3MF to STEP gives a faceted body for CAD, about 1 KB per triangle. To pack a mesh, STL to 3MF writes the file in millimetres. For the format itself, read the 3MF file guide; CAD parts belong in the STEP viewer.
Questions and answers
Why open a 3MF file online instead of in a slicer?
The page runs on any computer with Chrome, including ones where you cannot install software. You also get weight, cost and a full mesh check in one panel.
Can this 3MF file viewer show several objects?
Yes. Info counts the separate parts in the model, and the mesh check covers all the geometry you see.
Does a .3mf store its size correctly?
The 3MF format writes its unit into the file, with millimetre as the default, which STL cannot do. When we save 3MF, the unit is millimetres.
Will the 3MF viewer open a Bambu project file?
A .gcode.3mf project does not open. Open the model .3mf it was sliced from, or export plain G-code and open it in the G-code viewer.
Can I slice the 3MF here?
Yes, the Slice button runs our FDM slicer in the tab. None of its printer profiles has been test-printed yet, so watch the first layer.