This works because the installer isn’t really damaged. So much for the “Damaged Installer” error message! Odds are good that the installation works perfectly. Then try your Mojave or High Sierra or Sierra installer again. Don’t worry about the day and month, just change the year. Just go to the System Preferences, then Date & Time, and uncheck the box that says “Set date and time automatically.” Then change the year to 2018. Try changing the date on your Mac to sometime in 2018– maybe your “damaged installer” will magically work. Trying to install Mojave or High Sierra or Sierra on a Mac, and getting messages about the installer being damaged– but you know it used to work? My guess: your installer isn’t damaged. Wouldn’t hurt to restart after downloading one of these installers, and before actually running them. (Remember, 10.13 and 10.14 installers will be waiting for you in the Applications folder.) If that doesn’t work, read the rest of this article and see if we have an answer for you. If you’re not ready to install, quit the installer, and come back later. The installer will try to run after downloading, so be ready for that. This time, the App Store button should say “Get.” Click that button to download the installer anew. Quit the Mac App Store app, then try the link (from above) again. Find the bad one in the Applications folder, with a name like “Install macOS High Sierra” or “Install macOS Mojave,” and put it into the Trash. You have to get rid of it, and install a new one. When you get there, if you see “Open” instead of “Get” it means you already have the installer. So throw away the old one, download the new one, and try again.Ĭlicking the High Sierra or Mojave link takes you to the Mac App Store. Your old installer isn’t going to work without some funky moves but the new ones probably will. Below: links to Apple’s pages, where you can download these installers yourself.

Try downloading a fresh copy direct from Apple. 2020 UPDATE: it seems that the installers that Apple is providing now work without you playing games with the date on your Mac.

Macos high sierra installer app