How to convert STEP to STL
- Drop your .step, .stp, .iges or .igs file on this page, or click to choose it.
- Check the parts list. Untick anything you do not want to print, like fasteners or a reference plate.
- Pick a mesh quality. Standard is right for almost everything; use Fine for small parts with visible curves.
- Choose STL, 3MF or OBJ and download. Open it in your slicer as usual.
Why a STEP file has to be converted at all
STEP and IGES describe exact curved surfaces, the way CAD programs think. A slicer only understands flat triangles. Converting means approximating each curve with triangles, which is called tessellation, and the quality setting is how closely those triangles are allowed to follow the true surface.
It runs in your browser
The converter is OpenCascade, the open-source CAD kernel behind FreeCAD, compiled to WebAssembly. It downloads once, about 3 MB, and then reads your file entirely on your own machine. Nothing is uploaded, which matters when the file is a client's part or an unreleased design.
Questions
Is my STEP file uploaded to a server?
No. The CAD kernel runs inside your browser and reads the file from your disk. There is no server on the other end and no account, so there is nowhere for the file to go.
Which mesh quality should I use?
Standard for most prints. Fine gives smoother curves on small or detailed parts at the cost of a bigger file. Draft is useful for a quick check or for very large assemblies. The panel shows the triangle count each time you change it.
Can I export only some parts of an assembly?
Yes. Every part in the file is listed with its name and CAD colour. Untick the ones you do not want and only the ticked parts go into the download.
What about units?
The converter reads in millimetres, which is what slicers expect. If your part comes in the wrong size, it was probably modelled in inches: the toolkit can rescale it by 25.4.
Does it work with SolidWorks, Fusion 360, Onshape, FreeCAD and Inventor?
Yes, as long as you export STEP or IGES from them, which all of them can. STEP (AP203 and AP214) is the most reliable choice.