The User Id is your NoMachine account and you use it to login to NoMachine Network, as well as to access other services on the NoMachine website. It is also also requirement for connecting to a NoMachine target machine over the NoMachine Network service. User Ids can also be saved as contacts in your Users book which follows you wherever you log in to the Network service. When connecting to a computer, the User Id is visible in the list of connected users in the system tray icon of the target machine. It is not possible to search for User Ids on NoMachine Network. Nor is it possible to identify the machines of a specific User Id by searching on Network.