How to Fix a Damaged macOS Installer

Creating a macOS installer on a bootable USB drive provides a convenient way of installing a fresh copy of macOS on multiple Macs, and also allows you to perform a clean installation quickly and easily.

Catalina
If you tried to run your installer recently and unexpectedly received an error that it is damaged and can't be used, then don't worry – keep reading for a simple and straightforward way to fix it.

Why is my macOS Installer Damaged?


If you tried to use a macOS installer in the last few days or weeks, you may have been met with an error message saying something like "This copy of the Install macOS Mojave.app application is damaged, and can’t be used to install macOS."

installer
As Apple explains in a newly published support document, the likely reason for the "damaged" error message is an expired certificate. Happily though, the fix is very simple.

How to Fix a Damaged macOS Installer


To fix the damaged installer, you should just download the installer again. Doing so will also ensure that you have all of the macOS updates that have been released since you made the original installer, meaning you won't have to update macOS immediately after the initial installation is complete.

You can find the latest official download links below for the last six versions of Apple's Mac operating system, all of which contain a new certificate that has not expired:
To learn how to perform a clean installation of macOS using the bootable USB drive method, click one of the following links: macOS Catalina, macOS Mojave, macOS Sierra.

Related Roundup: macOS Catalina


Top Rated Comments

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4 weeks ago


That message does not mean you can't download it.
It only means that the installer won't run on that system version.
You will see that message after the download is complete (because the system automatically tries to launch the installer)
And, you have the downloaded installer, in your Applications folder. I would save the installer app to an external drive, and use one of the methods to create a fresh bootable installer from that app.
Finally, delete the downloaded installer from your boot drive.


Actually, I get that message BEFORE it tries to download it. I'm well aware that you can still download the file and create USB Installers and whatnot.. Gotta have the file downloaded first, though. And I'm not able to get that far.
Rating: 4 Votes
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3 weeks ago


Right this had baffled me and a colleague for a few days. The issue im having, now I understand the cause of the error, is that the links send you to the App Store and it just announces that it cant connect to the store. It will if I go to an app thats there. Any clues folks


The only way I was able to get the App Store installers was by going through a Virtual Machine of 10.14 and downloading them from there, and then copying them over.
Rating: 1 Votes
Avatar
4 weeks ago


Too Bad we can't download older versions of macOS on the App Store now.

That message does not mean you can't download it.
It only means that the installer won't run on that system version.
You will see that message after the download is complete (because the system automatically tries to launch the installer)
And, you have the downloaded installer, in your Applications folder. I would save the installer app to an external drive, and use one of the methods to create a fresh bootable installer from that app.
Finally, delete the downloaded installer from your boot drive.
Rating: 1 Votes
Avatar
4 weeks ago
This might be a stupid question, but I have noticed the installers are .dmg files and not .app files like when they come from the App Store. How do I make a bootable installer with terminal now? Could someone please explain this to me? That would help me out a great deal.
Rating: 1 Votes
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16 hours ago at 06:40 pm


I was able to make USB installers of everything from Yosemite on up to Catalina, accept for Sierra.


Did you want to say except for Sierra right?

Thanks
Came
Rating: 1 Votes
Avatar
4 weeks ago


So at what point can we assume Apple has updated the certificate on those installers and redownload?


# ProductID Version Build Post Date Title
1 061-36794 10.15 19A603 2019-10-21 macOS Catalina
2 041-91758 10.13.6 17G66 2019-10-19 macOS High Sierra
3 041-88800 10.14.4 18E2034 2019-10-23 macOS Mojave
4 061-26589 10.14.6 18G103 2019-10-14 macOS Mojave
5 041-90855 10.13.5 17F66a 2019-10-23 Install macOS High Sierra Beta
6 061-26578 10.14.5 18F2059 2019-10-14 macOS Mojave
Rating: 1 Votes
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4 weeks ago


Another weird problem I'm having is the error: ''..... is not a valid mount point'' in terminal. It only happens when I want to make a Sierra bootable installer, all the others work fine. Changing the name of the USB drive does not solve the issue and I've checked the path and it's correct. Does anyone else has this issue with the new 10.12 Sierra installer?


Indeed. I was so curious about your post that I downloaded Sierra and attempted to make the bootable usb to see if this bug is reproducible.

I got the same result.

The reproducibility of the bug makes it very suitable to apple for a bug report.

I have submitted the bug report to apple.
Rating: 1 Votes
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4 weeks ago
I cannot download macOS Catalina right now.

macOS Catalina, 10.15:

[URL unfurl="true"]https://apps.apple.com/us/app/macos-catalina/id1466841314?mt=12[/URL]

"The requested version of macOS is not available."
Rating: 1 Votes
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4 weeks ago
For those having issues downloading, you may want to look into the "installinstallmacos.py" script.
Rating: 1 Votes
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4 weeks ago


Thanks for the reply, but how do I make those bootable? I can't paste the creat install media terminal command right?

Why not? Works for me, and is how I normally make installers for anything later than probably Yosemite (10.10)
Or, use one of the apps that are designed to do that. I was using one called Install Disk Creator. You can find that here - https://macdaddy.io/install-disk-creator/
I used that same app on Sierra up to Catalina apps just today, and it works every time. I even tested the bootable USB for each version, and they actually booted (as you might expect)
Rating: 1 Votes
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