The STEP format is probably the most used accurate 3D geometry exchange format. (It can contain a lot more than just geometry!)

STL files (most often used in 3D printers) are based on triangles, which are basically only an approximation of the real geometry.

A lot of available STEP-file viewer are windows-only. I’ve been looking for a simple STEP-file viewer for UNIX-like operating systems, so that I can see the parts that I’m making using cadquery (see also: cadquery documentation).

I’m not a fan of IDE’s like cq-editor or IDE’s in general. In particular, cq-editor pulls in the whole of spyder (a Python IDE) just to get syntax highlighting in its built-in editor.