Slicers print triangle meshes, not CAD solids. If you downloaded a part as STEP or designed it in Fusion 360 or SolidWorks, converting STEP to STL is the step between the CAD model and your 3D printer. This converter runs entirely in your browser: the file is processed on your own device and never uploaded.
Why convert STEP to STL?
Slicers print triangle meshes, not CAD solids. If you downloaded a part as STEP or designed it in Fusion 360 or SolidWorks, converting STEP to STL is the step between the CAD model and your 3D printer.
How it works
Drop your .step file above and download the .stl. The conversion engine (Open CASCADE, compiled to WebAssembly) runs inside the page, so it works the same on Windows, macOS, Linux and ChromeOS without installing anything.
STEP vs STL
STEP (ISO 10303): STEP is the ISO standard for exchanging exact 3D solid models. It describes geometry as precise mathematical surfaces (B-rep and NURBS), not triangles, so a cylinder is stored as a true cylinder. Used by: Mechanical design tools such as SolidWorks, Fusion 360, Inventor, CATIA, Creo, Onshape and FreeCAD — it is the default “send me the model” format between them.
STL (stereolithography): STL, introduced in 1987 for 3D Systems’ stereolithography machines, describes a surface only as a list of triangles. It carries no colour, no materials and no units. Used by: Every 3D-printing slicer — Cura, PrusaSlicer, Bambu Studio, Chitubox — and model sites like Printables and Thingiverse.
Quality notes
STEP and IGES describe exact curved surfaces; STL and OBJ can only hold triangles. The converter tessellates every surface into a triangle mesh, so a perfect cylinder becomes many flat facets. The feature history, parametric dimensions and assembly metadata do not survive — only the shape does. STL has no units: slicers assume millimetres, which matches almost all mechanical CAD, but check the size after import. Closed STEP solids produce watertight meshes that print cleanly.
Common use cases
Printing a bracket downloaded from a supplier; sending a Fusion 360 part to a print farm; checking a customer’s STEP file fits your printer bed.
Frequently asked questions
Why does my printed part look faceted?＋
STL stores triangles, so curved faces are approximated. Tessellation turns each curved face into many small flat facets.
Will the model be the right size?＋
The geometry keeps its coordinates. STL has no unit field, so slicers read the numbers as millimetres — correct for nearly all mechanical STEP files.
Can I convert an assembly?＋
Yes, when the assembly is in one file: all its solids are meshed into one STL. Assemblies whose top file only references parts stored in separate files cannot be read — export a single-file STEP from your CAD tool.
Is my design uploaded?＋
No. OpenCASCADE runs inside your browser as WebAssembly; the STEP file never leaves your device.