What happens to your 3MF.

Your file

When you upload a project, it is written to a temporary folder on the server, converted, and offered back to you as a download. It is never added to a library, an account, or any permanent storage, and it is never shared with anyone else.

The upload, the converted result and the JSON report are deleted 10 minutes after the conversion. A background task sweeps expired files every minute, so this happens whether or not anyone else visits the site. Everything is also destroyed when the server restarts.

They are also deleted as soon as the converted project has been downloaded twice, whichever comes first. The second download is served in full and the files are removed immediately afterwards, so a download link cannot be used a third time and cannot be passed on to anyone else. Fetching the preview image or the JSON report does not count towards this; only the converted project itself does.

Anything that is not a genuine 3MF is discarded immediately. The server opens the file and checks it is a real 3MF package before doing any work; if it is not, the upload is deleted at once and never reaches the converter.

Uploads are limited to 64 MB.

How the converter works

A 3MF project is a ZIP archive holding the model geometry, its placement and a set of slicer settings. 3MFBridge opens your file, identifies which slicer and printer produced it, and rebuilds it around the bundled profile for the printer you selected.

Your model, its parts, placement, object metadata and previews are carried across unchanged. Machine-critical settings — nozzle and bed temperatures, build volume, motion limits and printer identity — are taken from the target printer's bundled profile rather than copied from your file. Settings that cannot be translated safely are dropped and listed in the report.

No G-code is copied from your file, and none is generated. The result is an editable project you open and slice yourself, which is why you should always check it before printing.

Every conversion produces a JSON report recording what was transferred, what was replaced, what was dropped and why. It is downloadable alongside the result, and is deleted on the same 10-minute schedule.

No accounts, cookies or trackers

There is no sign-up and no login. The site sets no cookies, and there is no analytics of any kind — no third-party scripts, no tracking pixels, no fingerprinting.

The only thing kept in your browser is your choice of dark or light theme, stored locally under 3mfbridge-theme. It never leaves your device.

Every asset on this site is served from this server. No fonts, scripts or images are loaded from third parties, and a Content-Security-Policy header enforces that.

What the server logs

Your IP address is never written to disk in full. The identifying part is stripped off before the request is logged: an IPv4 address keeps only its first three blocks and an IPv6 address only its first three, so 203.0.113.47 is stored as 203.0.113.0. What is left identifies a network, not a person, and cannot be traced back to you.

The access log therefore holds the time, the page requested, the response status and your browser's user-agent string. It contains no cookies, and nothing about the name or the contents of your file. The converter itself records no addresses at all.

Your full address is held in memory while the request runs, to apply a rate limit that stops one visitor overloading the server, and is discarded the moment the request finishes. It is never stored. If the server hits an unexpected fault it may write a full address into its error log; those entries exist only to diagnose the fault.

Where the server is

3MFBridge runs on a single server hosted by Hetzner Online GmbH in Helsinki, Finland. There is no CDN and no third-party proxy in front of it, so your file goes to that machine and nowhere else.

Contact

Questions about any of the above, or about a specific conversion, are welcome at 3mfbridge@gmail.com.

Because results are deleted within minutes, there is normally nothing left for us to look at after the fact. If you are reporting a conversion problem, keep the JSON report from that conversion and attach it — it records what was transferred, replaced and dropped, without containing your model.