Longtime macOS users will know that even though the Mac has a built-in recovery partition, it’s always useful to have a dedicated USB drive with a macOS installer. I am a big fan of using a tool like DiskMaker X to create them to keep around if I need to wipe a drive and reinstall macOS quickly. If you have a drive created for Mojave, Sierra, and High Sierra, know that a certificate has expired. If you are getting an error similar to “This copy of the Install macOS Mojave.app application is damaged, and can’t be used to install macOS”, read on to learn how to fix it.

If you’re getting the above error message when you go to install macOS, you’ll likely experience some panic about what to do. Thankfully, it’s an easy fix. As first reported by OSXDaily.com, a fix is quite simple.

The cause of this error is an expired certificate, and because the certificate is expired, the “Install macOS” app for Mojave, Sierra, and High Sierra will not run. Fortunately, there is a fairly simple solution to the “damaged” installer problem.

Below are the download links for the recent versions of macOS.

Mojave Installer

High Sierra Installer

Sierra Installer

You may need to reboot the Mac after you have downloaded the new (and valid certificate) installer application, particularly if you had already launched a version that showed the application damaged error message.

If you are new to making macOS boot drives, we’ve got articles to help.

Another benefit to making a new boot drive is that you’ll get all of the various macOS updates that have been released since you made your last one. It’ll make your installation process a lot faster if you are recovering from a dead hard drive, since you won’t need to install macOS and then apply patches right afterward. While the process of repairing the “This copy of the Install macOS Mojave.app application is damaged, and can’t be used to install macOS” isn’t fun, thankfully, it’s easy.

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