Convert STL to 3MF (Free)
Also converts OBJ, GLB, PLY, USDZ, WRL, STEP 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 STL to 3MF
- 1
Open your .stl file
Drag it onto the viewer above, or click "Open an STL 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 STL into 3MF, and what does not.
| Geometry | Kept | Both formats store triangle meshes, so the shape transfers directly. |
|---|---|---|
| Colors and materials | N/A | STL files carry no color, so the 3MF comes out in the viewer’s default material. You can color it in the destination application. |
| Units and scale | Kept | 3MF stores an explicit unit. STL 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: Stereolithography (.stl)
A single triangle soup. STL stores no color, no units, no parts and no layers, only the surface.
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 STL 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.
Frequently asked questions
▶Is this STL to 3MF converter free?
Yes. No signup, no watermark, no per-file limit and no paid tier. Innerscene.
▶Is my STL 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?
STL files carry no color, so the 3MF comes out in the viewer’s default material. You can color it in the destination application.
▶Will the 3MF open at the right size?
3MF stores an explicit unit. STL does not, so the size is taken from how the viewer read the file. Check the scale once on import.
▶How large an STL 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 STL?
Yes, the other direction works too. Bear in mind that anything the first conversion dropped is not restored by converting back. 3MF → STL
▶Which browsers does it work in?
Chrome, Edge, Firefox and Safari, on Windows, macOS, Linux, iOS and Android. No plugin and no extension.
Convert STL to something else
Convert something else to 3MF
Or start from the universal 3D viewer.