OwlCAD is a parametric 3D modeler for people designing parts to 3D print, and it runs entirely in the browser. I built it after outgrowing Tinkercad: gears, threads and curved profiles were a fight, and changing a dimension after grouping meant rebuilding the part. Fusion 360 solves that, but it's a big install for a bracket.

What you can do with it: model with dimensions that stay editable, so changing a value rebuilds the part. Use fit presets from tight to loose, and run a print check that shows overhangs, thin walls and whether the mesh is watertight before you slice. Pull gears, threads, hinges, enclosures and Gridfinity bins from 33 generators. Sketch with constraints, add per-edge fillets and chamfers, sweep, loft, and build assemblies with mates and a bill of materials. It also reads and runs OpenSCAD.

Files: imports STL, 3MF, OBJ, STEP and OpenSCAD; exports STL, 3MF, OBJ, GLB, STEP, DXF and SVG.

Under the hood: React and Three.js for the viewport, Manifold compiled to WebAssembly for the booleans (in a Web Worker, so the UI stays responsive), and OpenCascade in WASM for STEP export.

Pricing: the editor and every export format are free, commercial use included, and you can start without an account. Pro is $12/month or $120/year and adds AI generation that produces an editable model instead of a mesh, chat-based edits, and a hosted MCP server so Claude Code, Claude Desktop or Cursor can build parts. Classrooms are free.