Erase and reinstall macOS
You can erase your Mac and use macOS Recovery, the built-in recovery system on your Mac, to reinstall macOS.
WARNING: Erasing your Mac removes all the information from it. Before you start, back up your Mac with Time Machine.
On a Mac with Apple silicon or an Intel-based Mac with the Apple T2 Security Chip
Your computer must be connected to the internet. If you’re reinstalling on a Mac notebook computer, plug in the power adapter.
Erase your Mac using Erase Assistant.
Restart your Mac.
Choose Apple menu > Shut Down, press and hold the power button until “Loading startup options” appears, select Options, click Continue, then follow the onscreen instructions.
In the Recovery app window, select Reinstall for your macOS release, click Continue, then follow the onscreen instructions.
On an Intel-based Mac without the Apple T2 Security Chip
Your computer must be connected to the internet. If you’re reinstalling on a Mac notebook computer, plug in the power adapter.
Choose Apple menu
In the Recovery app window, select Disk Utility, then click Continue.
In Disk Utility, select the volume you want to erase in the sidebar, then click Erase in the toolbar.
Type a name for the volume in the Name field, click the Format pop-up menu and choose APFS, then click Erase Volume Group.
When the erase process is complete, click Done, then choose Disk Utility > Quit Disk Utility.
In the Recovery app window, select Reinstall for your macOS release, click Continue, then follow the onscreen instructions.
If you want to erase your Mac without reinstalling macOS, in order to restore it to factory settings before you trade it in or sell it, see Erase your Mac.