Gatekeeper helps to protect your Mac from apps that could adversely affect it.
Some apps, downloaded and installed from the Internet, could adversely affect your Mac. Gatekeeper helps to protect your Mac from such apps. Gatekeeper checks, if an App you want to start, was signed with an Apple Developer certificate and checks the integrity of the app. This ensures, that the app wasn’t modified after the app was signed by the developer. This also ensures, that the developer is known by Apple.
How to fix it
macOS 13 - 14
- Open “System Preferences”
- Go to “Privacy & Security"
- At “Allow apps downloaded from”
- You can choose “App Store” or “App Store and identified developers” (which is needed when you want to install and start App from outside the App Store but are signed with a developer certificate)
- The third option is not normally show since macOS 10.12 (you see it only when Gatekeeper is off)
macOS 10.11 – 12
- Go to “System Preferences” > “Security & Privacy” > “General”
- “click on the lock to make changes”
- At “Allow apps downloaded from”
- You can choose “App Store” or “App Store and identified developers” (which is needed when you want to install and start App from outside the App Store but are signed with a developer certificate)
- The third option is not normally show since macOS 10.12 (you see it only when Gatekeeper is off)
Further reading: https://support.apple.com/en-us/HT202491
