With macOS Recovery, you can easily reinstall your Mac operating system, even if you need to wipe your boot disk first. All you need to do is connect to the Internet. If there is an available wireless network, you can select the appropriate network from the Wi-Fi menu in the menu bar. macOS Recovery also offers this menu.
1. Booting from macOS Recovery
To start via macOS Recovery, turn on your Mac and immediately press and hold one of the following key combinations on your keyboard. ⌘-R is usually recommended, especially if you have never installed macOS Sierra 10.12.4 or later.
⌘ (⌘)-R
Install the latest macOS installed on your Mac.
Option-⌘-R
Upgrade to the latest macOS compatible with your Mac.
Shift-Option-⌘-R
Install the macOS that came with your Mac or the version closest to it that is still available.
Release these buttons when you see a logo, a spinning globe, or a prompt asking for your firmware password. When you see the Utilities window, you have launched with macOS Recovery. 2.
Determine if you want to wipe (format) your discs
If you need to wipe your disc before installing macOS, select Disc Tools from the Utilities window and tap Continue. You may not need to wipe your discs unless you are selling or giving away your Mac, or if you have a problem that requires you to wipe your discs. Learn more about when and how to wipe a disc. 3.
Installing macOS
After booting from macOS Recovery, follow these steps to install macOS.
1. Select Reinstall macOS (or Reinstall OS X) from the Utilities window.
2. Tap “Continue” and follow the on-screen instructions to select a disk and begin the installation.
If the installer asks you to unlock your disc, enter the password you used to log in to your Mac. If the installer does not recognize your disc or indicates that it cannot be installed on your computer or volume, you may need to wipe the disc.
3. Do not put your Mac to sleep or close the top cover for the installation to complete. During the installation process, your Mac may restart several times and display a progress bar, and the screen may go blank for several minutes at a time.
If your Mac restarts and you enter the Setup Assistant, but you are selling or giving away the Mac, press ⌘-Q to exit the Assistant without completing setup. Then tap Shutdown. When the new owner starts the Mac, they can use their own information to complete setup.
If you’ve never installed macOS Sierra 10.12.4
If macOS Sierra 10.12.4 or later has never been installed on your Mac, macOS Recovery works differently.
⌘-R is still the recommended method for booting through macOS Recovery. This key combination ensures that the installation is not associated with your ID, which is important if you are selling or giving away your Mac.
Option-⌘-R will install the macOS that came with your Mac or the version closest to it that is still available.
Shift-Option-⌘-R is not available.