Free Online STL to 3MF Converter
STL and 3MF solve different problems. STL stores a raw triangle soup: three vertices per facet plus a normal.
Converting to 3MF makes sense when your slicer needs mesh geometry with explicit units.
Preview in 3D
How to convert STL to 3MF
Select your STL file
Choose one model and its companion material, buffer and image files when applicable. The combined upload limit is 50 MB.
Check the preview and options
Check orientation, dimensions and required resources. Image reliefs are previewed after conversion; set their width and depth first.
Convert and download 3MF
Convert, then inspect the result and any warnings. Textured OBJ results download as a ZIP containing the OBJ, MTL and textures.
Why choose this converter
Real mesh conversion
Geometry is parsed and exported into the destination format.
Inspect the result
Use the preview, output statistics and format warnings to check the conversion.
Server conversion
A server mesh pipeline converts geometry. OBJ resources are returned together in a ZIP.
Static model scope
Animations, rigs, CAD construction history and unsupported material extensions are outside this converter's scope.
What Is a STL File? / 3MF
STL
STL stores a raw triangle soup: three vertices per facet plus a normal. There is no index buffer, no colour, no material and no unit. Because the format is so minimal, virtually every slicer, printer and CAD tool reads it, which is exactly why it is still the default handoff for 3D printing.
- Universally supported by slicers and printers
- Dead simple to parse and stream
- Binary variant keeps file size predictable
- No colour, texture or material information
- Duplicated vertices inflate file size
- No unit or scene hierarchy
3MF
3MF is the modern replacement for STL, stewarded by the 3MF Consortium. It is a ZIP of XML parts, so it carries units, colour, multiple objects, materials and print settings — everything STL throws away.
- Keeps units, so scale is unambiguous
- Colour, materials and multiple objects
- Compact compared with an equivalent STL
- Older slicers may not read it
- ZIP+XML is more work to parse than STL
- Still no animation
STL vs 3MF
| Property | STL | 3MF |
|---|---|---|
| Encoding | binary or ASCII | ZIP + XML |
| Colour | No | Yes |
| Texture maps | No | Yes |
| Materials | No | Yes |
| Animation | No | No |
| Units | No | Yes |
| Best for 3D printing | Yes | Yes |
| Best for the web | No | No |
| Best for game engines | No | No |
Before you convert
- Confirm the source really is STL — a renamed file will not parse.
- Check the bounding box in the preview; conversion does not fix a wrong scale.
- Decimate dense meshes before converting if the target is a slicer.
Common problems
The upload is rejected
Check the file really is STL and is under 50MB.
The preview is empty
The file is probably corrupt or uses an unsupported feature. Re-export it from the source application.
The result looks different from the original
Read the format notes above — some loss is inherent to the target format, not a conversion error.
Frequently Asked Questions
Can I convert STL to 3MF here?
Yes. Select the file and any companion resources, check the preview, then convert and download.
Is an account or payment needed?
No. Available conversions are free and do not require an account.
What is the file size limit?
50 MB combined, with at most one model and 63 companion files.
Will materials and textures survive?
This conversion exports geometry. STL and this service's 3MF writer do not retain materials or textures; PLY may retain vertex colors. Use GLB when materials are required.
Are animation and rigs preserved?
No animation or rig preservation is promised. Browser conversions export static meshes; check proprietary material features and real-world scale in the result.
Are uploaded models published?
No. Conversion does not add models to the public gallery. Browser USDZ export stays local; server conversions use temporary download files.