Are my files uploaded to a server?

No. This conversion runs entirely inside your browser using your own device’s processing power. The file never leaves your computer or phone, which is why it also works when your connection drops.

Does the size stay right?

Yes. 3MF states its units and the geometry is written out at the same real-world scale, so the print comes out the size it was meant to be.

Why would I go from 3MF back to STL?

Because a slicer or a print service asked for STL. 3MF is the better format; STL is the one more places accept.

Convert 3MF to STL

Runs on your device · Your file never leaves your device.

3MF is the modern printing format — it holds colours, units and print settings that STL never could. But plenty of slicers and print services still ask for STL. This converts one to the other in the browser.

You are going backwards in capability on purpose, and the tool is honest about what that costs: colour and any print metadata in the 3MF do not survive into the STL, because the format has nowhere to keep them. The geometry and its real-world scale do survive, which is what the printer needs.

The conversion runs on your own machine, which for a 3D file is the whole point: a model is usually a client’s product, a scanned property or something not yet announced. Nothing is sent to a server, so there is nothing to delete afterwards and nothing to take anyone’s word for.

How to convert 3MF to STL

Drop the 3MF file — and its companion files if it has any.
Check that STL is selected.
Press Convert.
Download the STL file.

Supported formats and limits

Input: 3MF
Output: STL
Companion files: MTL and texture images are used when you add them
Keeps animation: No — the format cannot store it
Where it runs: In your browser; the model is never uploaded

Not for: Carrying print settings or colour — those are the reasons 3MF exists, and STL cannot hold them.

Frequently asked questions

Are my files uploaded to a server?: No. This conversion runs entirely inside your browser using your own device’s processing power. The file never leaves your computer or phone, which is why it also works when your connection drops.
Does the size stay right?: Yes. 3MF states its units and the geometry is written out at the same real-world scale, so the print comes out the size it was meant to be.
Why would I go from 3MF back to STL?: Because a slicer or a print service asked for STL. 3MF is the better format; STL is the one more places accept.

Other ways to get a STL

GLB to STL

Related tools

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