IntoSTL

Free browser tool

Convert STL to 3MF

Turn a binary or ASCII STL into a 3MF model while keeping the conversion entirely on your device.

Private by design. Your STL is processed locally in your browser.

Choose an STL file to begin.

STL files do not include unit metadata. IntoSTL treats STL units as millimeters.

Your 3D preview will appear here.

How it works

STL to 3MF in three steps

  1. 1
    Upload an STL

    Choose a binary or ASCII STL up to 50 MB.

  2. 2
    Inspect the geometry

    Preview the parsed mesh, including disconnected shells.

  3. 3
    Download the 3MF

    Save the converted model as a standard 3MF file.

Conversion details

Geometry and units

The conversion carries mesh geometry into 3MF and keeps separate shells. STL files do not include unit metadata, so the source values are treated as millimeters.

3MF is useful when the next application prefers a modern container format. The new file does not invent colors, materials or print settings that were not present in the STL.

Common questions

STL to 3MF FAQ

Can IntoSTL read both binary and ASCII STL?

Yes. Binary STL is supported directly, and the existing Three.js STLLoader fallback handles valid ASCII STL when required.

What units does the converter use?

STL files do not include unit metadata, so IntoSTL treats STL units as millimeters when creating the 3MF file.

Are disconnected shells kept?

Yes. Separate shells in the source mesh remain part of the converted 3MF geometry.