How to reinstall OS X

How to install OS X 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 take these additional steps to reinstall OS X in a way that cleans your Mac of anything associated with you, your data, or your Apple ID.

  1. Start up from OS X 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 OS X Utilities window.

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

  3. Choose Reinstall OS X from the OS X Utilities window, then follow the onscreen instructions.
    This installs the OS X that came with your Mac when it was new. This version isn't associated with your Apple ID. The new owner can then use the Mac App Store to upgrade OS X with their Apple ID.
    OS X Utilities window
  4. When done, your Mac restarts to a setup assistant. Press Command (⌘)-Q, then click Shut Down. That way the new owner can complete the steps of the setup assistant using their own information.

If you're reinstalling for other reasons

OS X can be installed over the same version or earlier version of OS X, without removing your data. You don’t need to remove or disable the existing system first.

  1. Start up from OS X Recovery by holding 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 OS X Utilities window.

  2. If you do want to erase your disk before reinstalling OS X, open Disk Utility from the OS X 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 OS X from the OS X Utilities window, then follow the onscreen instructions.
    This installs the latest version of OS X that was previously installed on your Mac.

Other ways to reinstall OS X:

  • If you made a Time Machine backup of your Mac, you can restore OS X from that backup. This erases the disk you're restoring, then replaces everything on that disk with OS X and other data from the backup. To proceed, start up from OS X Recovery, then choose Restore From Time Machine Backup and follow the onscreen instructions.

  • Or open the App Store on your Mac, then click Purchased in the toolbar to see items that you previously downloaded with your Apple ID. Find the currently installed version of OS X in the list, then click the Download button. After downloading, the OS X installer opens automatically. 

Learn more

To download and reinstall OS X using OS X 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 OS X Recovery. If the connection is using WPA/WPA2, you can use OS X Recovery or OS X 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 OS X Recovery but not OS X Internet Recovery. 

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

Last Modified: