Locking the screen is instantaneous, and the Mac will require a password to login and regain access.

Choose “Lock Screen” to instantly lock the Mac screen and bring up the login window.Pull down the  Apple menu from any application.You can enable the Lock Screen on Mac OS from anywhere via the Apple menu: If you’re on an earlier version of Mac OS system software, you’ll need to rely on other methods to initiate the lock screen on a Mac as described here, or if you have a MacBook Pro with Touch Bar you can set a dedicated screen lock button.

Note this specific Lock Screen feature is only available in the latest versions of Mac OS, including macOS Big Sur, Catalina, Mojave, or High Sierra 10.13.x or later. This is an excellent privacy and security feature, and one that Mac users should familiarize themselves with if they frequently use their computers in a public setting, be it at work, school, home, or anywhere else they may want to password protect their computer to prevent unwanted access. Once Lock Screen has been enabled, a proper user login and password must be entered before the Mac can be accessed again. With the new Lock Screen feature, you can instantly lock down a Mac through a system-wide menu option, or with a keyboard shortcut.

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