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

How to convert STL to 3MF

The STL to 3MF converter supports binary STL and valid ASCII STL, then packages the parsed geometry as a 3MF model without uploading the source file.

  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

What changes when STL becomes 3MF?

The STL geometry is carried into a 3MF mesh, preserving the geometry represented by the source file. Separate, disconnected shells can remain disconnected within that converted geometry.

The container changes, but missing information does not return. The new 3MF does not recreate colors, materials, textures or print settings that STL never contained.

Scale handling

STL units and millimeter handling

STL files do not include unit metadata. IntoSTL treats the numeric values in the source STL as millimeters and writes the 3MF using millimeter units.

For example, a source dimension of 20 is handled as 20 mm. Check the preview and the dimensions in your next application if the STL originated in software that assumed a different unit.

Modern workflows

Why convert STL to 3MF?

3MF is a modern container widely supported by current slicers and 3D-printing workflows. Converting can be useful when another application prefers 3MF for import, organization or later processing.

This conversion modernizes the file container while keeping the source geometry; it does not enrich the model with information the STL did not provide. If you later need an STL again, use the related 3MF to STL converter.

Common questions

STL to 3MF FAQ

Can IntoSTL read both binary and ASCII STL?

Yes. IntoSTL supports both binary STL and valid ASCII STL files.

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.

Does conversion restore colors or print settings?

No. Converting STL to 3MF does not recreate colors, materials, textures or print settings that are missing from the source STL.