Convert STL to STEP (Free)
Also converts OBJ, GLB, PLY, USDZ, 3MF, 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 STL to STEP
- 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 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 STL 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 | N/A | Neither format carries color, so there is nothing to lose. |
| Units and scale | Kept | STEP 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. |
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: Stereolithography (.stl)
A single triangle soup. STL stores no color, no units, no parts and no layers, only the surface.
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 STL 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 STL to STEP 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 STEP export?
Neither format carries color, so there is nothing to lose.
▶Will the STEP open at the right size?
STEP 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 STEP back to STL?
Yes, the other direction works too. Bear in mind that anything the first conversion dropped is not restored by converting back. STEP → 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 STEP
Or start from the universal 3D viewer.