Anytime you log into a computer, whether it's when you're sitting at the keyboard or when connecting remotely over a network, you must authenticate yourself as an authorized user of that computer. This is typically done with a username/password pair. (With Screens, you can also authenticate secure connections by designating a private SSH key.)
When using Screens to connect to a Mac, it logs in using an existing user account on that Mac, so it's critical that you enter the correct authentication credentials when establishing one-off connections to a Mac or when creating a saved screen for the connection in the Screens Library.
When you first set up your Mac, you entered your full name and created a username. The username is sometimes called a short name since it is usually a shorter version of your full name. When asked for your username — for example, in the macOS log-in window or when connecting for file sharing or screen sharing — you can enter either your full name or your username.
The username is used by your Mac to keep track of all your files and information. Because of this, the username is permanent -- it cannot be changed.
If you can’t remember your username, open a Finder window and look for the house icon in the sidebar. The house icon identifies your home folder, which is named with your username.
If you don’t see the house icon:
- Launch Finder.
- In the app menu, click Finder.
- Click Preferences.
- Click Sidebar.
- Under Favorites, select your home folder.
Another way is via Terminal:
- Launch Terminal
- Type whoami
The command should return your username:
Authorizing your user to access your Mac
You may also need add your user in the allowed list of these services:
- Screen Sharing/Remote Management (VNC)
- Remote Login (SSH)
For more details, consult this article.
When Screens connects to a Windows computer, it is actually connecting to a VNC/SSH server running on that computer. To authenticate with Screens, you must use the credentials configured in the VNC/SSH server, not your Windows username/password.