Turn your screen saver on or off

If you use a screen saver, it starts automatically after your computer is inactive for a time. You can also choose a shortcut so your screen saver starts when you move the pointer to a corner of the screen.
  1. Choose Apple menu > System Preferences, click Desktop & Screen Saver, and then click Screen Saver.
  2. Click Hot Corners.
  3. Choose Start Screen Saver or Disable Screen Saver from the pop-up menu for a corner you want to use; and then click OK.
  4. To use the Command (⌘), Control (^), Option (⌥), or Shift (⇧) key together with a hot corner, press the key while the pop-up menu is open. For example, if you press the Shift key, the Start Screen Saver command changes to ⇧-Start Screen Saver.
To deactivate the screen saver and return to the desktop, press any key, move the mouse, or touch the trackpad. If your screen saver is a slideshow, press the Spacebar to pause and resume.

You can lock your screen by requiring a password to turn off a screen saver.
To keep the information on your Mac secure when you are away from it, set it to require authentication when it wakes from sleep. When you return to your Mac, type your login name and password to continue working.
  1. Choose Apple menu > System Preferences, click Security & Privacy, and then click General.
  2. Select “Require password... after sleep or screen saver begins.”
You can adjust the amount of delay before a password is required in the pop-up menu.

To lock your screen quickly with fast user switching enabled, choose Login Window from the menu with your user name. Your applications will remain open and undisturbed, but your computer islocked.

Locking the screen doesn’t prevent other users from turning off the computer and restarting it, and then logging in to their own accounts. If you think this could happen, be sure to save your work before you leave your computer.

You can use your administrator name and password to unlock the screen for your own account or the account of a standard user, but not the account of another administrator.