Choosing the Correct Way to Reinstall macOS
Your first reinstallation choice should always be to reinstall macOS without erasing your boot drive. This approach preserves your user files by replacing macOS system files with known good versions. If this doesn’t fix your problem, you can erase the boot drive and perform a fresh reinstall. Only use a bootable USB installer to reinstall macOS if you can’t boot into Recovery Mode at all.
How to Reinstall macOS Using Recovery Mode
The standard method for reinstalling macOS is through Recovery Mode, which boots from a separate recovery partition on your boot drive that macOS creates at the time of installation. You’re unable to change the partition. To unlock the boot partition, macOS boots up from the recovery partition. You’re free to make changes and adjustments to your primary boot partition in the recovery partition, including completely erase it or reinstall macOS. To boot into Recovery Mode, restart your Mac. Hold down Command+R as soon as your Mac shuts off and while the computer starts up. Release the keys when you see the Apple logo, a progress wheel, or a password prompt.
How to Reinstall macOS Without Erasing Everything
If your macOS installation causes problems, you don’t have to wipe the disk entirely and start over from scratch. The macOS can reinstall only the system files, replacing any corrupted or damaged system files. Boot into Recovery Mode and select Reinstall macOS from the macOS Utilities application. Then select Continue to begin the installation process. Follow the on-screen instructions to reinstall macOS.
How to Erase and Reinstall macOS
Wipe your hard drive and start completely clean with an erase and reinstall. Format with Disk Utility, and then reinstall macOS.
Other Recovery Mode Options
By default, Recovery Mode enables the reinstallation of your macOS installation with the version of macOS installed on your Mac. But you can also access different installation tools that install different versions of macOS. You access these modes by holding modifier keys while booting into Recovery Mode:
Command+R: Boot into Recovery Mode and reinstall the latest version of macOS on your Mac.Option+Command+R: Boot into online Recovery Mode, which downloads the latest compatible version of macOS and installs it on your Mac. If your recovery partition is damaged or can’t reinstall the macOS version currently on your Mac, this network recovery can restore the installation with a fresh file download.Shift+Option+Command+R: Boot into Recovery Mode to install the macOS version that shipped with your Mac or the closest available version.
Reinstall macOS Using a Bootable Installer
If your Mac has become so nonfunctional that you can no longer boot into Recovery Mode, never fear. You can reinstall macOS from a bootable USB installer. It’s a complex process that requires at least one working Mac. You need a full version of the macOS installer and a USB drive formatted for macOS Extended with at least 12 GB of space. Use Disk Utility to format your USB before proceeding, if needed.
