When end users log in to a Connection Server instance for which the Hide domain list in client user interface global setting is enabled, the Domain drop-down menu is hidden in Horizon Client and users provide domain information in the Horizon Client User name text box. For example, users must enter their user name in the format domain\username or username@domain.
On a Windows client system, a registry key determines whether the last user name is saved and displayed in the User name text box the next time a user logs in to the server. To prevent the last user name from being displayed in the User name text box and exposing domain information, you must set the value of the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\dontdisplaylastusername registry key to 1 on the Windows client system.
For information about hiding security information in Horizon Client, including the Domain drop-down menu and server URL information, see the topics about global settings in the Horizon 8 Administration document.