How to reinstall macOS

How to install the Mac operating system again on the same Mac.

If you're selling or giving away your Mac

Begin by completing the other steps to prepare for selling or giving away your Mac. Then follow these steps to reinstall macOS in a way that clears your Mac of anything associated with you, your data, or your Apple ID.

  1. Start up from Internet Recovery by holding down Option-Command (⌘)-R immediately after turning on or restarting your Mac. Release the keys when you see the Apple logo. Startup is complete when you see the utilities window.

  2. Open Disk Utility from the utilities window, then use Disk Utility to erase your built-in hard disk using the Mac OS Extended (Journaled) format. Quit Disk Utility when done.

  3. Choose Reinstall macOS (or Reinstall OS X) from the utilities window, then follow the onscreen instructions.
    This installs the system that came with your Mac when it was new. It isn't associated with your Apple ID, so the new owner can use the App Store to upgrade to a later version using their Apple ID.

  4. When done, your Mac restarts to a setup assistant. Press Command-Q, then click Shut Down. The new owner can then complete the steps of the setup assistant using their own information.

If you're reinstalling for other reasons

You can install macOS over the same version or earlier version, without removing your data. You don’t need to remove or disable the existing system first.

  1. Start up from macOS Recovery by holding down Command (⌘)-R immediately after turning on or restarting your Mac. Release the keys when you see the Apple logo. Startup is complete when you see the utilities window.

  2. If you want to erase your disk before reinstalling, open Disk Utility from the utilities window, then use Disk Utility to erase the disk. Quit Disk Utility when done. 
    Erasing the disk isn't necessary unless you're transferring your Mac to a new owner, partitioning your disk for use with Boot Camp, or attempting to resolve an issue that Disk Utility can't repair

  3. Choose Reinstall macOS (or Reinstall OS X) from the utilities window, then follow the onscreen instructions.
    This installs the latest version of macOS that was previously installed on your Mac.

Other ways to reinstall macOS:

Learn more

To download and reinstall macOS using macOS Recovery, you need a broadband Internet connection that meets the following requirements. If you don't know what to do, try a different Internet connection, such as at your work or another home.

  • The connection is configured to use DHCP over Wi-Fi or Ethernet, not PPPoE (if there is no router handling the PPPoE connection).
  • The connection is not using 802.1X or other certificate-based authentication.
  • The connection is not using a proxy server configured in Network preferences.
  • If the connection is using the WEP or WPA-Enterprise security protocols, you can use macOS Recovery. If the connection is using WPA/WPA2, you can use macOS Recovery or macOS Internet Recovery.
  • If the connection is using a captive network, such as a network that displays a login or agreement page before you can access the Internet, you can use macOS Recovery but not macOS Internet Recovery. 

When you download macOS using macOS Recovery, your computer's serial number is sent to Apple to help authenticate your request.

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