Unlike iOS, where you can only install apps from app store, macOS users have an option to download apps directly from developers’ or third-party websites. But for apps not downloaded from the app store to run, the developer has to be verified or ‘notarized’ by Apple. Not all developers are verified, of course, and if you try to run an app on macOS Sierra or later, you will see different errors stopping you from using that app.
Three such errors are ‘this app is damaged,’ ‘this app can not be opened because the developer can not be verified,’ and ‘this app can not be opened because Apple can’t check it for malicious software.’ When macOS is sure an app contains malware, it will show ‘this app will damage your computer. You should move it to trash’ error.
These errors are actually designed to prevent malicious apps from running on your Mac but can also prevent apps not verified by Apple from loading. Apple decided to be more defensive against apps that were not downloaded from the app store with the launch of macOS Sierra in 2016. Before Sierra, you could simply turn on an option to allow apps from ‘anywhere’ and run apps by unidentified developers.
You can still run these ‘unverified’ apps on your Mac but you have to follow additional steps to be able to do so. In this article, I am sharing some quick ways to fix apps that won’t open on macOS.
1. Disable Gatekeeper
Gatekeeper is the safety mechanism of macOS that decides which apps are allowed to run. As mentioned earlier, recent versions on macOS only let you run apps from app store or from identified developers. By disabling Gatekeeper, you will bring back the option to run apps from ‘anywhere’ meaning apps by unverified developers.
This requires a quick command in Terminal. Open Terminal and type the following command. When it prompts, enter your password.
sudo spctl --master-disable
There is no message displayed after you run this command successfully. But you can verify if it worked by navigating to Settings > Security & Privacy > General. You should see three options now. Select ‘Anywhere’ and you are done.
Now open the app you were unable to run and it should show you a message suggesting the app is from unverified developer. Click Open and it should run as expected. Do this for all apps that weren’t working before.
Once you successfully run an app that wasn’t opening earlier, you should enable Gatekeeper again. Your apps will continued to work after that. To enable Gatekeeper, use the following command.
sudo spctl --master-enable
This command works in all versions starting from macOS Sierra to the latest macOS Big Sur.
2. Control-click An App
While leaving Gatekeeper turned off could leave your Mac open to risks, there’s another way to open unverified or ‘damaged’ apps. This approach involves adding the app in question to an ‘allow’ list or exempting it from further scrutiny. The following screenshot shows macOS Catalina stopping me from running Syncthing app.
To add an app to the list of apps exempt from gatekeeper checks, open Finder and click Applications from left pane. Find the app in question. Press and hold Control key and right click on the app. Click open while Control key is still pressed and release Control key.
The message that asked me to move the app to the bin because it couldn’t be verified will now ask me if I was sure about opening it. Click Open on the prompt that appears on screen and it should run as expected.
For each app that wouldn’t open, you have to perform Control-click-open just once. After the app is exempt from Gatekeeper checks, it will continue to run without showing errors. If you update the app to newer version, macOS might stop it from loading again but you can simply perform this step in that case.
This method, too, works in all recent macOS versions including the latest macOS Big Sur.
Solving ‘This App is Damaged’ or ‘Developer Can’t be Verified’ Errors in macOS: Summary
Because of the tightened security in macOS Sierra and later, apps not downloaded from app store or from a verified developer may be blocked from running. If you run into these errors, you can either disable Gatekeeper or add the app to exemption.
After doing so, an app downloaded from unverified developers will run as expected. These workarounds work on macOS Sierra, High Sierra, Mojave and Catalina as well as macOS Big Sur.
You should be careful when running apps not downloaded from app store or the official website of the developer. These apps might be altered to include malicious code and could harm your Mac. You should only allow apps you trust to run on your computer.
That’s all, folks. I hope you found this tutorial helpful and I’d like to thank you for reading.