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.

Top Rated Comments

gank41 Avatar
26 months 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.
Score: 4 Votes (Like | Disagree)
chrfr Avatar
25 months ago

I am sure that I already had been looking and can't seem to find and it's puzzles me..
It could be on any drive attached to your computer.
Score: 3 Votes (Like | Disagree)
gank41 Avatar
26 months 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.
Score: 2 Votes (Like | Disagree)
tywebb13 Avatar
26 months 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.
Score: 2 Votes (Like | Disagree)
bsbeamer Avatar
26 months ago
For those having issues downloading, you may want to look into the "installinstallmacos.py" script.
Score: 2 Votes (Like | Disagree)
tywebb13 Avatar
26 months ago

The createinstallmedia command will fail with the new Sierra installer. Some code is munged somewhere. As a workaround, do an actual installation to your flash drive, then just copy the new installer to that drive's Applications folder. At least you can boot and get Sierra installed to an otherwise unbootable drive (or reinstalled over an earlier installation nondestructively).
Thank you. I too have a workaround. Make a bootable DVD installer instead.

To do this copy and paste these into terminal to make the bootable iso file (assuming you have the Sierra installer in your Applications folder):

hdiutil attach /Applications/Install\ macOS\ Sierra.app/Contents/SharedSupport/InstallESD.dmg -noverify -nobrowse -mountpoint /Volumes/install_app

hdiutil create -o /tmp/Sierra.cdr -size 7.85g -layout SPUD -fs HFS+J

hdiutil attach /tmp/Sierra.cdr.dmg -noverify -nobrowse -mountpoint /Volumes/install_build

asr restore -source /Volumes/install_app/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase

rm /Volumes/OS\ X\ Base\ System/System/Installation/Packages

cp -rp /Volumes/install_app/Packages /Volumes/OS\ X\ Base\ System/System/Installation/

cp -rp /Volumes/install_app/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System/BaseSystem.chunklist

cp -rp /Volumes/install_app/BaseSystem.dmg /Volumes/OS\ X\ Base\ System/BaseSystem.dmg

hdiutil detach /Volumes/install_app

hdiutil detach /Volumes/OS\ X\ Base\ System/

hdiutil convert /tmp/Sierra.cdr.dmg -format UDTO -o /tmp/Sierra.iso

mv /tmp/Sierra.iso.cdr ~/Desktop/Sierra.iso

A bootable iso file called Sierra.iso will then appear on your desktop and you can use this to burn it to a dual layer dvd:

sudo drutil burn /Users/YOURNAME/Desktop/Sierra.iso

where you replace "YOURNAME" with the username for the account you are logged into at the time.

and then boot to startup manager with option key to select the dvd.

Just be aware though that a bootable dvd takes a lot longer to boot up than a bootable usb.
Score: 2 Votes (Like | Disagree)

Related Stories

studio buds family

Beats Studio Buds Debuting Today With Active Noise Cancellation, Stemless Design, and More for $150

Monday June 14, 2021 8:00 am PDT by
We've seen a lot of teasers about the Beats Studio Buds over the past month since they first showed up in Apple's beta software updates, and today they're finally official. The Beats Studio Buds are available to order today in red, white, and black ahead of a June 24 ship date, and they're priced at $149.99. The Studio Buds are the first Beats-branded earbuds to truly compete with AirPods...
YouTube Picture in Picture Feature

YouTube Premium Subscribers Can Now Use iOS Picture-in-Picture: Here's How

Wednesday August 25, 2021 3:55 am PDT by
Google has rolled out picture-in-picture support as an "experimental" feature for YouTube premium subscribers, allowing them to watch video in a small window when the app is closed. If you're a premium YouTube subscriber looking to try out picture-in-picture, follow these steps: Launch a web browser and sign into your YouTube account at YouTube.com. Navigate to www.youtube.com/new. Scroll...
M1X MBP Feature

Leaker: Upcoming MacBook Pro to See Price Hike Over Current Model, Equal Performance Across 14 and 16-Inch Sizes

Tuesday August 24, 2021 5:28 am PDT by
The upcoming 14-inch MacBook Pro is set to be more expensive than the current 13-inch MacBook Pro and both the 14 and 16-inch models will offer the same performance, according to the leaker known as "Dylandkt." The leaker shared the information on Twitter, explaining that both of the upcoming MacBook Pro models, expected to come in 14 and 16-inch sizes, will feature the same performance due...
youtube apple tv

YouTube Discontinuing 3rd-Generation Apple TV App, AirPlay Still Available

Wednesday February 3, 2021 3:09 pm PST by
YouTube is planning to stop supporting its YouTube app on the third-generation Apple TV models, where YouTube has long been available as a channel option. A 9to5Mac reader received a message about the upcoming app discontinuation, which is set to take place in March.Starting early March, the YouTube app will no longer be available on Apple TV (3rd generation). You can still watch YouTube on...
ryanscoolios13thumbnail

Apple Releases iOS 13.1.3 With Bug Fixes for Phone, Mail, Health, and More

Tuesday October 15, 2019 10:09 am PDT by
Apple today released iOS 13.1.3 and iPadOS 13.1.3, minor updates to the iOS 13.1.2 software that was released two weeks ago. This is the fourth update to the iOS 13 operating system that came out in September. The iOS and iPadOS 13.1.3 updates are available on all eligible devices over-the-air in the Settings app. To access the updates, go to Settings > General > Software Update....
Top Stories 75 Thumbnail

Top Stories: Last-Minute iPhone 13 Rumors, Apple Announces App Store Changes, and More

Saturday September 4, 2021 6:00 am PDT by
The finish line is in sight! Apple's annual iPhone event is likely just a week or so away and all eyes will be on the company as it unveils the next version of its most popular product line. With any luck, we'll also see the next-generation Apple Watch and perhaps even some new AirPods. Other news this week saw Apple making some more changes to its App Store policies in response to a...
affinity designer contour tool

Serif Updates Affinity Photo, Designer, and Publisher With New Tools and Functions

Thursday February 4, 2021 1:58 am PST by
Serif today announced across-the-board updates for its popular suite of Affinity creative apps, including Affinity Photo, Affinity Designer, and the Apple award-winning Affinity Publisher for Mac, all of which were among the first professional creative suites to be optimized for Apple's new M1 chip. "After another year which saw record numbers of people switching to Affinity, it's exciting to...
iPhone 13 Dummy Thumbnail 2

Kuo: iPhone 13 to Feature LEO Satellite Communications to Make Calls and Texts Without Cellular Coverage

Sunday August 29, 2021 7:39 am PDT by
The iPhone 13 will feature low earth orbit (LEO) satellite communication connectivity to allow users to make calls and send messages in areas without 4G or 5G coverage, according to the reliable analyst Ming-Chi Kuo. In a note to investors, seen by MacRumors, Kuo explained that the iPhone 13 lineup will feature hardware that is able to connect to LEO satellites. If enabled with the relevant...
maxresdefault

Craig Federighi and Greg Joswiak Discuss iPadOS 15, macOS Monterey, Privacy, Shortcuts on Mac, and More

Saturday June 12, 2021 6:12 am PDT by
As is tradition, Apple executives Craig Federighi and Greg Joswiak joined Daring Fireball's John Gruber in an episode of The Talk Show to discuss several announcements that Apple made over this weeks WWDC, including iPadOS 15, macOS Monterey, and a large focus around privacy. Federighi kicks off the conversation discussing the common architecture, now thanks to Apple silicon, across all of...
iOS 14 on iPhone feature emergency

Apple Seeds Third Betas of iOS and iPadOS 14.6 to Developers [Update: Public Beta Available]

Monday May 10, 2021 10:13 am PDT by
Apple today seeded the third betas of new iOS and iPadOS 14.6 updates to developers for testing purposes, one week after seeding the second iOS and iPadOS 14.6 updates. iOS and iPadOS 14.6 can be downloaded through the Apple Developer Center or over the air after the proper profile has been installed on an iPhone or iPad. iOS and iPadOS 14.6 appear to be more minor changes focusing on...