How to Fix 'macOS Could Not Be Installed on Your Computer' Error

All is not lost if you encounter this particular error

The "macOS could not be installed on your computer" error is one of the last ones you want to see. It pops up when you're trying to update your Mac's operating system, but can't complete the operation. Despite the wording, it doesn't mean your installation will never work. It just means it failed that one time.

The bad news is this error could be occurring due to a number of different reasons. The good news is you can get your Mac back up and functional with just a little work.

What Causes the 'macOS Could Not Be Installed' Error?

Several issues could cause the problem. Luckily, the error screen itself should give you some idea of what's gone amiss.

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Free-Photos/Pixabay 

Here are some messages you might see underneath the warning:

  • "The pat /System/Installation/Packages/OSInstall.mpkg appears to be missing or damaged."
  • "An error occurred installing macOS."
  • "Unable to unmount volume for repair."
  • "Storage system verify or repair failed."
  • "An error occurred while verifying firmware."

Some of these offer more information than others, but they point to different stages of the installation that have failed. The following steps and fixes should be able to sort out any of the aforementioned problems.

How to Fix the 'macOS Could Not Be Installed' Error

  1. Restart and try the installation again. This may seem counterintuitive to redo the thing that just didn't work, but sometimes a restart is all your Mac needs to sort itself out.

  2. Check the Date & Time setting. If the displayed date and time don't match reality, this could be the problem. Restart your Mac again if necessary, then go to System Preferences > Date & Time. Click the lock icon and enter your password (if necessary) to enable changes, then click Set date and time automatically. After this, try the installation again to see if it works.

    Set date and time automatically checkbox in macOS
  3. Free up space. In some cases, macOS will fail to install because it doesn't have enough room on your hard drive to do so. To see how much you have available, click the Apple logo > About This Mac > Storage. You'll see a breakdown of what's living on your computer.

    Hover your mouse over the white space at the right side of this bar to learn exactly how much space is free. If that seems a little low, you might want to move some non-essential files off temporarily to see if that lets the installation proceed.

    Storage tab in macOS

    Later versions of macOS also include a "Manage" option that will offer suggestions and guidance to help you find things to get rid of.

  4. Delete the installer. Find the macOS Installer in your Finder's Downloads folder, drag it to the Trash, then download it again and retry.

    You may need to force restart your Mac by holding down the Power button until it shuts down. Afterward, turn the Mac back on. You may also want to hold down Shift during the restart to boot up in Safe Mode so the Installer doesn't try to run again.

  5. Reset the NVRAM. This is a tiny chunk of memory that stores basic information like the time, monitor resolution, and which disk to start up from. You may need to go back into your System Preferences to switch any settings this changed, but you can try the installation again before that to make sure the problem is resolved.

  6. Restore from a backup. If you use Time Machine to regularly back up your Mac, you can try going back to an earlier state to see if it's more compatible with the installer.

    1. Make sure your backup drive is attached, then restart your computer and hold Command+R until the Apple logo appears. Instead of going to the Desktop, your computer will prompt you to choose the main language, then open a window called macOS Utilities.
    2. In macOS Utilities, click Restore From Time Machine Backup, then click Continue.
    3. You'll come to an intermediate screen with some information about what you're about to do. Click Continue to move ahead.
    4. Choose the drive you store your backups to and click Continue again, which will take you to a screen where you can choose your most recent backup. Afterward, click Continue again.
    5. Your computer will restore the earlier backup, and you can see if the installation works.
  7. Run Disk First Aid. This may help if you're getting the "Unable to mount volume" error. First Aid will check your internal hard drive and make any fixes it can. It may even be able to mount the volume after it's done. Then you'll be able to retry the installation.

    First Aid button in Disk Utility on macOS
  8. If none of the above worked, it may be time to turn your computer over to the professionals. Check out our guide on how to get your computer fixed for instructions on finding someone to solve the problem and what you need to do to prep your mac for servicing.