How to reinstall macOS
Use macOS Recovery, your computer’s built-in recovery system, to reinstall the Mac operating system.
Reinstall macOS from macOS Recovery
Back up your Mac, if possible. Reinstalling macOS doesn't remove your apps or personal data, but it’s still a good idea to make a backup first.
From the list of options in Recovery, select the option to install or reinstall macOS. Then click Continue and follow the onscreen instructions.
If the installer asks to unlock your disk, enter the password that you use to log in to your Mac.
If the installer offers the choice between installing on “Macintosh HD” or “Macintosh HD - Data”, choose Macintosh HD.
If the installer doesn't see your disk, quit the installer, choose Disk Utility from the list in Recovery, then use Disk Utility to erase your startup disk. If Disk Utility can’t see the disk or erase it, your Mac might need service.
Allow installation to complete without putting your Mac to sleep or closing its lid. It might restart and show a progress bar several times, and the screen might be empty for minutes at a time.
After installation, your Mac might start up to a setup assistant. Follow the steps in the setup assistant. However, if you're selling, trading in, or giving away your Mac, quit the setup 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.
Which macOS will be installed?
On a Mac with Apple silicon:
Recovery installs the current version of the most recently installed macOS.
If you installed a macOS upgrade and then used Disk Utility to erase the disk, you might get the macOS that you were using before upgrading.
On an Intel-based Mac:
If you used Command-R to start up from the local Recovery system, you get the current version of the most recently installed macOS.
If you used Option-Command-R to start up from Internet Recovery, you might get the latest macOS that is compatible with your Mac.
If you used Shift-Option-Command-R to start up from Internet Recovery, you might get the macOS that came with your Mac, or the closest version still available.
If macOS installation is not successful
Learn what to do if an error occurred while installing macOS. Your Mac must have a broadband internet connection that uses DHCP over Wi-Fi or Ethernet. Some network connections can prevent installation from Recovery, including those that use a required captive-network login, 802.1X security, or PPPoE (unless a router is handling the PPPoE connection).
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