To hide a SQL Server instance, we need to make a change in SQL Server Configuration Manager. To do this, we have to follow the below steps:
First, in SQL Server Configuration Manager, we have to expand 'SQL Server Network Configuration'
Right-click on Protocols for and select 'Properties'
Once we do that, we will find a 'HideInstance' box in which, on the 'Flags' tab, we have to select 'Yes'
After that, click on 'OK'
Note: While hiding a named instance, we need to provide the port number in the connection string so that even if the browser is running it is possible to connect to the hidden instance.