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