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3MF to STL Converter

Convert a 3MF file to an STL. The page reads the objects, their plate positions and the file’s units, writes them to one STL in millimetres, and checks that it is watertight before you can download it.

  1. 1Drop the file
  2. 2Check it
  3. 3Download STL

1Drop your 3MF file

Drop a .3mf file here, or choose one. It stays on your device.

Open a file to check it

Turns on when the STL has been read back and is watertight. Binary STL, millimetres.

Your file is unpacked and read by this browser tab. Nothing is uploaded, and the STL is saved straight from this page.

2About this file

  • Kept: every mesh and component, with its position on the plate and the file’s units.
  • Dropped: colours, materials, slicer settings and supports. STL can’t store them.
  • All objects go into one STL file, at their plate positions.

3Size and direction

Size

3MF files state their units, and this page reads them.

mm

Which way is up

How to convert 3MF to STL

  1. Drop the 3MF. Project files saved from a slicer work if they contain meshes.
  2. Look at the plate. Everything on the build plate goes into one STL, in the positions saved in the file.
  3. Read the check, then download. The button turns on when the STL passes.

What is in a 3MF file

A 3MF is a zip archive with the model written as XML, plus units, plate positions and often colours and slicer settings. STL is only a list of triangles. Going from 3MF to STL keeps the shape and loses everything else, so keep the original 3MF as your master copy.

Several objects on one plate

An STL has no idea of separate objects, so a plate of five parts becomes one STL holding five separate shells. The page shows the count as Separate parts. Most slicers can split them apart again.

Parts that overlap

If parts on the plate touch or overlap, the edges where they meet may count as non-manifold, and the download stays off. Move them apart in your slicer, or export them separately, and try again.

What the check proves

The download button starts off. The page writes the STL, reads those bytes back the way another program would, joins corners that match to 0.0001 mm, and only turns the button on if every edge joins exactly two faces and the size matches. If it doesn't pass, you see how many open and non-manifold edges there are, and you can run the simple repair. The repair closes holes and turns faces, and it can change the shape, so it only runs if you press it. Some files can't be fixed this way, and those need Blender or MeshLab. The check is about the file, not about how it will print.

FAQ

How do I convert 3MF to STL?

Drop the 3MF here and press Download STL once the check passes. No software to install and no account. You can also export STL from most slicers, if you have the project open already.

Does converting 3MF to STL lose anything?

It keeps the shape and drops the rest: colours, materials, slicer settings and supports. Keep the 3MF if you may need those later.

Is 3MF better than STL?

3MF holds more: units, several objects, colours and settings, and in less space. STL is simpler and works almost everywhere, which is why people still convert to it.

Will my 3MF stay the right size?

Yes. The page reads the unit stated in the file and writes the STL in millimetres. The size above the check is what is in the STL.

Why does my 3MF project have no geometry?

Some slicer files hold only a sliced plate or point to data the page can’t read. Export the model from your slicer as a plain 3MF or STL.

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