ICn3D
From Proteopedia
iCn3D, "I see in 3D", is a powerful macromolecular structure viewer provided by the US National Center for Biotechnology Information. It works within a web browser. It has extensive menus, as well as a command language. To start the program, go to the iCn3D Website.
Commands can be entered within a session, or appended to a URL web address so as to customize an initial view. For example, here is a link including commands that shows an Electrostatic potential map of protein 1pgb.
iCn3D was preceded by a standalone program Cn3D, which is being phased out after its last update in March, 2023.