Resolving 'Install MacOS Application is Damaged' Errors with Mac OS System Installers

When trying to install a new operating system on your Mac, you may encounter an error message that states 'This copy of the Install macOS 'High Sierra' application is damaged, and can't be used to install macOS.' This frustrating issue can occur due to an expired certificate in the installer package. Fortunately, there are ways to resolve this problem.

Method 1: Re-Downloading the Installer

The simplest solution to the 'damaged' installer problem is to re-download the installer from Apple's website or App Store. The new installer will contain a fresh certificate that is not expired, allowing you to successfully install macOS High Sierra on your Mac. To download the updated installer, follow these links:

* Find macOS High Sierra from Apple here: 'direct link'

* Find macOS Mojave from Apple here: 'App Store link'

* Find macOS Sierra from Apple here: 'direct App Store link'

Method 2: Modifying the Application Installer

Another approach to resolving the 'Install MacOS Application is Damaged' error message was left by reader Howard in the comments. This method involves modifying the application installer using tools like Suspicious Package and pkgutil, which can show the expired certificate that causes the error.

To use this method, you will need to investigate the `pkg components` of the MacOS Installer to see specifics about the expired certificate. If you have already launched a version of the installer that showed the 'application damaged' error message, you may need to reboot your Mac after downloading and installing the new, valid certificate installer.

By following these simple steps, you can resolve the 'Install MacOS Application is Damaged' errors and successfully install macOS High Sierra on your Mac.

Mac os high sierra update