Convert U3D to 3MF (Free)
Also converts STL, OBJ, GLB, PLY, USDZ, WRL from the same file.
Runs in your browser. No upload, no signup, nothing to install.
Also from Innerscene: Circadian Lab, a free lighting calculator for room illuminance, melanopic EML, and glare.
How to convert U3D to 3MF
- 1
Open your .u3d file
Drag it onto the viewer above, or click "Open a U3D File". Files up to 200 MB open directly; the parse runs in a worker so the page stays responsive.
- 2
Pick 3D Manufacturing Format in the Export menu
Click Export in the toolbar, then 3MF (.3mf).
- 3
Download
The .3mf is written in the browser and saved straight to your downloads folder. No queue, no email, no watermark.
What survives the conversion
A file conversion is a translation, and formats do not carry the same things. Here is exactly what moves from U3D into 3MF, and what does not.
| Geometry | Kept | Both formats store triangle meshes, so the shape transfers directly. |
|---|---|---|
| Colors and materials | Reduced | U3D can hold material colors and 3MF holds one color per object, so materials are flattened to that. |
| Layers and structure | Reduced | 3MF has named objects but no layers, so each layer becomes a named part instead. |
| Units and scale | Kept | 3MF stores an explicit unit. U3D does not, so the size is taken from how the viewer read the file. Check the scale once on import. |
| Lines and points | Dropped | 3MF geometry is manifold mesh only, so line work and point clouds are skipped. |
What the 3MF writer emits: An OPC package in millimeters, Z-up, with each mesh as its own named object carrying a basematerials color, placed by a build item.
The source: U3D (Universal 3D) (.u3d)
The meshes of an ECMA-363 U3D file, or of the U3D model inside a 3D PDF, with each node placed, its material colours and the progressive-mesh detail resolved to the full level. A PDF with several 3D annotations opens the first model.
The target: 3D Manufacturing Format (.3mf)
The modern replacement for STL: named parts, per-object color, and units that are actually in the file.
Opens in: PrusaSlicer, Bambu Studio, Cura, Windows 3D Builder, Fusion 360.
Your file never leaves your computer
Both the U3D parser and the 3MF writer are JavaScript and WebAssembly running in your own browser tab. There is no upload step, no server-side conversion queue, and no copy of your file anywhere but your machine. That matters for drawings under NDA, for client work, and for anything you would not email to a stranger.
Free to Use, No Signup
There are no accounts and no watermarks on this converter. If it saved you time, the one thing we ask is a mention: a post, a link from your blog or course page, or a reply to someone asking how to open a file.
Share it
Made something reusable? Add it to the Free Parts Library. Writing about it? Copy a link, badge or citation. Send us your post and we’ll feature it with a link to your site.
Hear about new formats
Occasional emails when the viewer learns a new format or gets a new tool.
Frequently asked questions
▶Is this U3D to 3MF converter free?
Yes. No signup, no watermark, no per-file limit and no paid tier. Innerscene.
▶Is my U3D file uploaded anywhere?
No. The file is read with the browser file API and converted in the same tab. Nothing is sent to a server unless you explicitly click Share, which is a separate, opt-in feature.
▶Will my colors and materials survive the 3MF export?
U3D can hold material colors and 3MF holds one color per object, so materials are flattened to that.
▶Do layers and named parts carry into the 3MF file?
3MF has named objects but no layers, so each layer becomes a named part instead.
▶Will the 3MF open at the right size?
3MF stores an explicit unit. U3D does not, so the size is taken from how the viewer read the file. Check the scale once on import.
▶How large a U3D file can I convert?
Up to 200 MB, and the ceiling adapts to how much memory your device reports. The conversion runs on your own hardware, so a desktop with plenty of RAM will handle more than a phone.
▶Can I convert 3MF back to U3D?
Not here. We read U3D and write 3MF, but not the reverse. the universal 3D viewer
▶Which browsers does it work in?
Chrome, Edge, Firefox and Safari, on Windows, macOS, Linux, iOS and Android. No plugin and no extension.
Convert U3D to something else
Convert something else to 3MF
Or start from the universal 3D viewer.