How to Reinstall MacOS

1. Start up from macOS Recovery

To start up from macOS Recovery, turn on your Mac and immediately press and hold one of the following combinations on your keyboard. Release the keys when you see an Apple logo, spinning globe, or other startup screen.

Command (⌘)-R

Reinstall the latest macOS that was installed on your Mac (recommended).

Option-⌘-R

Upgrade to the latest macOS that is compatible with your Mac.

Shift-Option-⌘-R

Reinstall the macOS that came with your Mac, or the closest version still available.   

You might be prompted to enter a password, such as a firmware password or the password of a user who is an administrator of this Mac. Enter the requested password to continue.

Select a user you know the password for

When you see the utilities window, you have started up from macOS Recovery.

2. Decide whether to erase (format) your disk

Choose to erase your disk if

  • You're selling, trading in or giving away your Mac
  • You have an issue that requires you to erase 

If you need to erase before installing macOS, select Disk Utility from the Utilities window, then click Continue. Learn more about when and how to erase.

Erasing a disk or volume permanently deletes all of its files. Before continuing, make sure that you have a backup of any files that you want to keep.

3. Install macOS

When you're ready to reinstall macOS, choose Reinstall macOS from the Utilities window. Then click Continue and follow the onscreen instructions. You will be asked to choose a disk on which to install.

  • If the installer asks to unlock your disk, enter the password you use to log in to your Mac.
  • If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
  • If the installer is for a different version of macOS than you expected, learn about macOS Recovery exceptions.

macOS Catalina installer window

Please allow installation to complete without putting your Mac to sleep or closing its lid. During installation, your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.

If your Mac restarts to a setup assistant, but you're selling it, trading it in, or giving it away, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.