I have a local PostgreSQL database that does not require authentication, but I cannot connect it through DbVisualizer when I leave 'Authentication' fields (Database Userid, Database Password) empty.
It shows the following error in Connection Message
An error occurred while establishing the connection:
Long Message:
FATAL: no PostgreSQL user name specified in startup packet
Details:
Type: org.postgresql.util.PSQLException
SQL State: 28000
DbVisualizer version is 9.5.6
As Laurenz Albe pointed out, I did need the username after all. By default it's 'postgres'.