Since the launch of macOS Sierra in 2016, Apple has tightened up the Gatekeeper security one very visible change thanks to this the option to allow apps from unidentified developers is no longer there.
This tight security causes some apps downloaded from sources other than the App Store to show ‘this app is damaged’ message. Another error you might see is ‘this app can’t be opened because it’s from an unidentified developer.’
Previously, you could simply change a setting and allow any app to run on your Mac. In macOS versions since Sierra (macOS Mohave and macOS Catalina), Apple no longer provides this option in Settings by default. But there’s still a way to bypass Gatekeeper and solve ‘this app is damaged’ error.
A Little Flashback
In previous versions of Mac OS X (now simply macOS), there used to be three options under Settings > Security & Privacy > General. The “Allow apps downloaded from:” area had options, namely: App Store, App store and identified developers, and Anywhere.
As the last option is now missing from settings, you’ll need to run a command in Terminal to loosen up Gatekeeper security of macOS. This will add the ‘Anywhere’ option back to where it used to be — allowing you to run apps downloaded from the internet.
Caution: The ‘This App Is Damaged’ message is not really an ‘error.’ It’s a ‘security feature’ designed to keep your Mac from running unauthorised apps that can possibly contain malware.
You should only allow third-party apps from developers you trust to run on your Mac. Mac App Store is the best way to download apps. If the app you wish to use isn’t available on App Store (like VLC media player or Skype), proceed with caution and only download it from the official website of that app.
How to Solve ‘This App Is Damaged’ Error in macOS Catalina, Mohave or Sierra?
To solve ‘this app is damaged’ error, simply open Terminal from Launchpad and enter the following command.
sudo spctl --master-disable
Enter your password and you’re done. Note that there are two (2) dashes before master. You might miss that while copy/pasting. So I will leave a screenshot below. I would suggest you type the command manually.
Also note that there is no output or message after you successfully execute the command. Open Settings and verify that the Anywhere option is now visible as shown below.
After this, you can install and run any app that gave you error and now you’d be asked if you wanted to run that app. Click Open and the app should load just fine — like it’s supposed to.
Reverting the Gatekeeper Settings
Once you disable Gatekeeper and run app(s) you want, you should change the security settings back to normal. Leaving Gatekeeper security turned off leaves the ‘gate’ open for other unauthorized apps as well and it’s recommended that you leave Gatekeeper on.
To enable Gatekeeper again, enter the following command (notice two dashes before ‘master’).
sudo spctl --master-enable
That’s it. You’ve reverted to default security settings. After this, you will still be able to run the app(s) that previously gave you error. If you install a new app after turning on Gatekeeper, you will have to turn it off again in order to run the new app(s).
Note that you should run all those apps which you couldn’t run at least once after disabling Gatekeeper, otherwise you won’t be able to run them after enabling it again.
That’s it folks. You were reading How to Solve ‘This App Is Damaged’ Error in macOS Sierra on techstuffer.com. I hope you found this tutorial worth your time and I’d like to thank you for reading.