If an error occurs while updating or installing macOS
The message may say that an error has occurred while downloading, preparing or installing, or that the installer is damaged or could not be verified.
The cause of messages like these can vary, and sometimes they are only temporary.
If the message recommends a solution, such as re-downloading the installer and trying again, please try that first. If the message says that your Mac doesn't have enough storage space, find out how to free up storage space. The other solutions, starting with the easiest, are listed here.
Check your internet connection
Even if you're not installing macOS from the internet, the installer needs the internet to get firmware and other information specific to your Mac. Make sure your Mac has a working and stable internet connection.
Install in safe mode
Install when your Mac has started up in safe mode. To start up in safe mode, determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:
Shut down your Mac.
Turn on your Mac and continue to press and hold the power button until you see the startup options window.
Select your startup disk, then press and hold the Shift key while clicking "Continue in Safe Mode".
Log in to your Mac. You may be asked to log in again.
Turn on or restart your Mac, then immediately press and hold the Shift key as your Mac starts up.
Release the key when you see the login window, then log in to your Mac.
You may be asked to log in again. On either the first or second login window, you should see "Safe Boot" in the top right-hand corner of the window.
Install after repairing your disk
Use Disk Utility to repair your startup disk. Then try updating or installing macOS again.
Install from macOS Recovery
Install while your Mac has started up from macOS Recovery. This will give you the latest version of the macOS currently or most recently installed. To start up from macOS Recovery, follow the appropriate steps:
Turn on your Mac and continue to press and hold the power button until you see the startup options window. Click the gear icon labelled Options, then click Continue.
Turn on your Mac and immediately press and hold Command (⌘)-R until you see an Apple logo or another image.
If you're asked to select a user you know the password for, select the user, click Next and enter their administrator password. When you see the utilities window in macOS Recovery, select Reinstall macOS, then click Continue and follow the onscreen instructions. Find out more about using macOS Recovery to reinstall.
Install after erasing your Mac
If no other solutions have worked, erase your Mac, then reinstall macOS or restore from a backup.
If the issue persists or you need help, please contact Apple Support.