How to Lock a Computer

Mac

1. 
   Open 'System Preferences'. Open the 'Apple' menu in the upper left corner and select 'System Preferences'.

   1. You can also launch it from the launchpad or quick launch bar at the bottom of the screen.
   2. Users running a recent version of MacOS or OSX will have had to create a password when setting up their computer. Users running older versions can create a password by going to 'Accounts' in the 'System Preferences' and selecting 'Change Password' next to the user account.
2. 
   Click 'Security and Privacy'. This is located in the top row of options.
3. 
   Select the 'General' tab. Tabs are listed along the top of the window.
4. 
   Click the the 'Lock' icon. This is located in the lower left corner and will prompt you to enter your password. Once entered, this will unlock the settings and allow them to be modified.
5. 
   Select the 'Require Password after sleep or screensaver begins' checkbox. This setting forces the user to enter a password after a selected amount of time has passed following the display entering sleep or screensaver.
6. 
   Select 'Immediately' from the dropdown. This is located next to the checkbox and will make it so the user must always enter a password after the display enters sleep/screensaver.

   1. You can select other time limits before a password is required from the dropdown menu. This can be useful if you want to be able to return from a display sleep quickly without entering your password. However, 'Immediately' is the only option that effectively 'locks' your computer on command.
7. 
   Select 'Disable Automatic Login' (for users on OSX 10.9 or earlier). Automatic login allows users to bypass password entry when booting the computer and waking from sleep. Disabling it ensures that a password prompt will appear when the screen is locked or slept.^{[1] X Research source}

   1. This feature was removed for Administrator accounts on OSX 10.10 and later.
   2. Optionally, you can click the Lock icon again to relock these changes, but they will be saved either way.
8. 
   Hit Ctrl+⇧ Shift+Power. This will lock your computer's screen without fully sleeping the computer. You will be prompted for your password upon any attempt to unlock.^{[2] X Research source}

   1. If your mac has an optical (CD/DVD) drive you can use Ctrl+⇧ Shift+⏏ Eject to perform the same action.