FreeCAD is a free and open-source CAD design software that allows you to view STP files. It can be used to view various other 2D/ 3D model files too, such as DWG, DXF, OBJ, DAE, PLY, IGS, IFC, STL ...

When you double-click on a file in Windows, it will automatically open a default program that is configured to manage these types of files. It is common, though, want or need to use a different ...