The Interfaces dropdown menu entry in the top toolbar contains lists all the interfaces that are currently monitored by ntopng. Among all interfaces listed, one has a check mark that indicates the interface is currently selected. Every data and information shown in ntopng web GUI relates to the currently selected interface. Any interface listed can be selected simply by clicking on its name.
The dropdown menu is only used to switch between selected interfaces, it is also used to actually see interface traffic statistics. Interface traffic statistics can be accessed by clicking on the currently selected interface.
A contextual menu with multiple options and badges appear right below the top toolbar. Menu entries are discussed below.