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Convert STL to 3MF, free and online

Drop an .stl file, look it over in 3D, and save a 3MF your slicer opens. It all runs on your device, so the file is never uploaded. Need to go the other way? Drop a 3MF and you get an STL back.

Drop an STL file here

or choose a file — writes a 3MF on the spot. Got a 3MF? Drop that instead to pull an STL out.

.STL · .3MF · max ~200 MB
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File—
Triangles—
Vertices—
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Want it in color? A plain STL or 3MF holds geometry only. Paint your model per-region in Layerpaint and export a Standard 3MF your slicer prints in multiple filaments.

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🔒 Files are processed locally in your browser and never uploaded.

STL to 3MF in one drop

STL has been the default 3D-printing file for years, but it only ever stores a list of triangles. 3MF is what Bambu Studio, OrcaSlicer and PrusaSlicer reach for now — a compact zip that can carry the mesh plus print settings, supports, multiple objects and color. Moving an old STL into a 3MF gives your slicer a tidier file to work from, and this tool does it from a single drop.

The work happens on your machine. Your .stl is read in the browser, the geometry shows up in the live 3D preview above, and the 3MF is zipped together locally for download. The file never leaves your device, which helps when you're handling a paid commission or a model you'd rather not hand to some random web service.

What the 3MF carries — and what it doesn't

Because an STL has nothing but triangles, the 3MF this tool writes is geometry-only too: the same shape, in the newer container. There's no print profile and no color baked in, since there was none to copy. If color is what you're after for multi-filament or AMS printing, don't stop at a plain 3MF — paint the model in Layerpaint and export a Standard 3MF your slicer reads as real filament assignments.

Going from 3MF back to STL

Drop a 3MF and the tool runs the other direction, writing a clean STL you can drop into any older tool that still expects one. It's a quick way to flatten a 3MF when you only need the shape — though any color in that 3MF is left behind, because STL can't hold it.

Questions

Why convert STL to 3MF?
3MF is the format modern slicers save by default. It's a compact zip that can hold print settings, supports, multiple objects and color, where an STL only ever stores raw triangles. Converting an old STL gives you a cleaner starting file in Bambu Studio, OrcaSlicer or PrusaSlicer.
Does the 3MF keep print settings or color?
No. This writes a geometry-only 3MF — the same shape your STL had, in the 3MF container. No print settings, no color, because the STL never carried any. To add color for multi-filament printing, paint in Layerpaint and export a Standard 3MF.
Will the 3MF open in Bambu Studio, OrcaSlicer or PrusaSlicer?
Yes. The output is a standard, geometry-only 3MF that imports cleanly into Bambu Studio, OrcaSlicer, PrusaSlicer and anything that reads 3MF. Units are millimeters, matching the STL.
Is my STL uploaded anywhere?
No. The file is read, converted and written to a 3MF entirely on your device in JavaScript. Nothing is sent to a server, so large or private models stay with you.
Can it convert 3MF back to STL?
Yes — drop a 3MF and you get an STL. Any color or per-object paint in the 3MF is dropped, since STL stores geometry only. Need the color kept? Open the file in the Layerpaint painter instead.