Free 3MF to STL online, and nothing is uploaded
The usual free 3MF to STL converter asks you to hand the file to a server. This one parses it in your browser instead — same result, and the file never leaves your machine.
Drop .3mf files here
or drag & drop — up to 150 MB each, multiple files supported
Free, but not by uploading your design
“Free online converter” usually means: drag a file in, hit convert, and trust that whoever runs the site deletes it later. That is a bet on someone else's retention policy. Here the file is opened by JavaScript in your own tab, so there is nothing to leak, delete or log.
What you get for free
- Binary or ASCII STL for every model, with no watermark added to the mesh.
- Batch queue — several .3mf files, one pass, and a ZIP of the results.
- No signup, no quota, no logins. Convert as often as you like.
- No install on macOS, Windows, Linux, iPad or Android.
The one honest limitation: 150 MB per file
Because conversion is local, the limit protects your tab rather than our disk. Very large 3MF packages often balloon from embedded textures and thumbnails, so re-exporting without them usually solves it. Split a huge assembly into per-object files and convert each part — the STL output for a single object is small.
Why the result is trustworthy
The converter walks the full 3MF build tree — nested components and per-item 4×4 transforms — and flattens every triangle with its world coordinates and normal. What comes out is geometry only: no colour, no material, no hidden extras. That is precise, but it also means holes in the source model will arrive as holes. Fix geometry in your modeller first; see the troubleshooting hub for the full list.
Privacy note: there is no upload endpoint to call. The site keeps no copy of your model, and closing the tab discards it immediately.
Pick your route afterwards
The STL is the same wherever you slice it. Compare the Cura workflow, PrusaSlicer notes, Bambu Lab route and the binary vs ASCII decision.
Frequently asked
Is this really free, with no signup?
Yes — no account, no quota, no charge. Convert one model or a whole queue, and download each STL or the batch as a ZIP.
What does "no upload" mean?
The 3MF is parsed and encoded in your browser tab. There is no upload endpoint, so nothing can be stored — not by us, not by a third party.
Are there watermarks in the STL?
No. The output is exactly your geometry — no extra facets, no note embedded in the header.
Why a 150 MB limit?
The cap protects your machine, since local conversion needs several times the file size in memory. Re-export without textures or split the model.