Not a viewer: this is upstream FreeCAD 1.1.3 compiled to WebAssembly, with every workbench, the OpenCASCADE geometry kernel, the Python interpreter and the FEM solvers running inside the tab — a 42 MB, 34-part 3D-printer assembly opens, and CalculiX solves a beam to within 1% of theory. The first load pulls about 115 MB, and no drawing leaves your machine. Chrome or Edge only for now; Firefox and Safari will work “the day they ship JSPI”. LGPL, from Virtastic.