If an error occurred while updating or installing macOS
The message might say that an error 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 to redownload the installer and try again, please try that first. If the message says that your Mac doesn't have enough storage space, learn how to free up storage space. The other solutions here are organized starting with the easiest.
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 that your Mac has a working and stable internet connection.
Install in safe mode
Install while your Mac is 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 might 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 might be asked to log in again. On either the first or second login window, you should see ”Safe Boot” in the upper-right 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 is started up from macOS Recovery. This gives 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 labeled Options, then click Continue.
Turn on your Mac and immediately press and hold Command (⌘)-R until you see an Apple logo or other image.
If you're asked to select a user you know the password for, select the user, click Next, then enter their administrator password. When you see the utilities window in macOS Recovery, select Reinstall macOS, then click Continue and follow the onscreen instructions. Learn more about using macOS Recovery to reinstall.
Install after erasing your Mac
If no other solutions work, erase your Mac, then reinstall macOS or restore from a backup.
If the issue persists or you need help, please contact Apple Support.