Convert 3MF to STEP (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 3MF to STEP
- 1
Open your .3mf file
Drag it onto the viewer above, or click "Open a 3MF File". Files up to 200 MB open directly; the parse runs in a worker so the page stays responsive.
- 2
Pick STEP AP214 in the Export menu
Click Export in the toolbar, then STEP (.step).
- 3
Download
The .step 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 3MF into STEP, and what does not.
| Geometry | Reduced | The triangles become a faceted B-rep: one planar face per triangle inside a closed shell. CAD reads it as real solid geometry with true units, but the faces stay faceted, they do not become NURBS surfaces. |
|---|---|---|
| Colors and materials | Dropped | STEP has no concept of color or materials, so the one color per object in your 3MF file are not written. The geometry is unaffected. |
| Layers and structure | Dropped | STEP is a single flat body with no layers or named parts. Everything merges into one object. If you need the structure, export to GLB, OBJ, DXF instead. |
| Units and scale | Kept | STEP stores an explicit unit, so the model opens at true size without rescaling. |
What the STEP writer emits: ISO 10303-21 AP214, each mesh written as a faceted B-rep: one planar face per triangle inside a closed shell, in millimeters under an explicit SI unit. Exact for polyhedral shapes, a faithful tessellation for curved ones.
The source: 3D Manufacturing Format (.3mf)
Named manifold objects with their per-object colors and explicit millimeter units.
The target: STEP AP214 (.step)
The neutral CAD exchange format every mechanical package imports.
Opens in: SolidWorks, Fusion 360, Inventor, CATIA, NX, Creo, FreeCAD, Onshape.
Your file never leaves your computer
Both the 3MF parser and the STEP 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 3MF to STEP converter free?
Yes. No signup, no watermark, no per-file limit and no paid tier. Innerscene.
▶Is my 3MF 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 STEP export?
STEP has no concept of color or materials, so the one color per object in your 3MF file are not written. The geometry is unaffected.
▶Do layers and named parts carry into the STEP file?
STEP is a single flat body with no layers or named parts. Everything merges into one object. If you need the structure, export to GLB, OBJ, DXF instead.
▶Will the STEP open at the right size?
STEP stores an explicit unit, so the model opens at true size without rescaling.
▶How large a 3MF 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 STEP back to 3MF?
Yes, the other direction works too. Bear in mind that anything the first conversion dropped is not restored by converting back. STEP → 3MF
▶Which browsers does it work in?
Chrome, Edge, Firefox and Safari, on Windows, macOS, Linux, iOS and Android. No plugin and no extension.
Convert 3MF to something else
Convert something else to STEP
Or start from the universal 3D viewer.