In GN4, you can sign in on more than one place with the same sign-in information. For example, you can sign in on your own computer, and then again, with the same name, on another computer.

Unlike GN3, in GN4 it is not possible to force the "one sign in only".

Signing into on more computers with the same user name

Two or more users can work simultaneously using the same user name. This is technically possible, but is might be prevented on the organizing level - keeping personal passwords private and secret. Following that simple rule you avoid disputes about who's the author of a wrong title.

Another rule to respect is: never leave unattended a computer with your sign in active, as all the operations are logged and someone else may appear to work under your sign-in information (user name and password).

Preventing users to sign in more than once on different computers

This is actually not possible.