3MF to STL Converter – Free, Private, In-Browser

3MF vs STL: what is the difference?

STL is the oldest and most widely supported 3D printing format. It describes a model as a plain list of triangles and nothing else: no units, no colors, no material, no information about which parts belong together. Because it is so simple, practically every slicer, CAD program and online print service can open it.

3MF (3D Manufacturing Format) was designed as a modern replacement. A 3MF file is a ZIP archive that contains XML model data, so it is usually much smaller than the same model in STL. It records the unit of measurement, can hold several objects with their positions, and can store colors, materials, thumbnails and even complete slicer projects. Bambu Studio, Orca Slicer and PrusaSlicer all save projects as 3MF by default.

Why convert 3MF to STL?

Compatibility. Some older slicers, CNC and CAD tools, online quote services and model marketplaces still only accept STL.
Editing. Mesh editors and sculpting tools often import STL more reliably than 3MF projects with many parts.
Splitting a project. A downloaded project may contain several objects on one or more plates. Exporting each object as its own STL lets you print, scale or remix them individually.
Sharing. STL is the safest format to send to someone when you do not know which software they use.

How to convert 3MF to STL with this tool

Drop your .3mf file onto the box above, or click it to choose a file. It opens instantly in the 3D preview.
Rotate and zoom to check the model, and read the overall size in millimetres to make sure the scale is right.
If the file contains several objects, untick the ones you do not need, or choose a plate from the plate menu.
Click Download STL to get one merged binary STL, or Each object as separate STL to get a ZIP with one file per object.

Objects keep the positions they had in the 3MF, so a merged STL reproduces the original layout. Your slicer can then re-arrange or split them again if needed.

Notes for Bambu Studio and Orca Slicer files

Project files saved by Bambu Studio and Orca Slicer store each object in its own model part inside the archive and reference it from the main model; this is called the 3MF production extension. The converter follows those references, applies every part's transform, and reads object names and plate numbers from the project's settings file, so the list shows the same names you see in the slicer.

Keep in mind what STL cannot hold. Painted multi-color regions, filament assignments, height-range modifiers, negative parts and print settings are not carried over. A multi-part object (for example a badge whose letters are separate parts for color changes) is exported as one STL containing all of its parts. Sliced files (.gcode.3mf) contain toolpaths rather than editable meshes and should be opened in the slicer instead.

Checking the STL before you print

After converting, open the STL in your slicer and compare the size with the dimensions shown above; they should match to a hundredth of a millimetre. If a part looks hollow or has missing faces, the problem was usually already in the original mesh, and most slicers can repair it automatically on import. Because the exported file is binary STL, it is also several times smaller than the text version some older tools produce.

Frequently asked questions

Is my 3MF file uploaded to a server?

No. The file is read and converted by JavaScript running in your own browser tab. Nothing is sent to a server, so the tool also works offline once the page has loaded.

Will colors and print settings be kept in the STL?

No. STL only stores triangle geometry, so colors, painted regions, materials, modifiers and slicer settings are dropped. If you need separate colors, export each object or part as its own STL and assign filaments again in your slicer.

Can I convert a Bambu Studio or Orca Slicer project 3MF?

Yes. Project files that store objects in separate model parts (the 3MF production extension) are supported, object names are read from the project, and if the project has several plates you can filter by plate before exporting.

What units does the exported STL use?

Millimetres. STL files have no unit field, and almost every slicer assumes millimetres, so the converter scales models saved in inches, centimetres or microns to millimetres automatically.

Is there a file size limit?

There is no fixed limit because nothing is uploaded. The practical limit is your device memory: typical print files of tens of megabytes convert in seconds on a laptop, while very large files may be slow on a phone.