Gatekeeper is a new security feature starting in Mac OS 10.8. See Apple's Website for more information about Gatekeeper features and benefits.
You can find Gatekeeper settings in System Preferences > Security & Privacy > General.
This document describes how to enable installation/launch of applications if you encounter launch errors via Mac OS X Background: By default, Mac OS 10.8.x, 10.9.x, 10.10.x, 10.11.x and macOS only allows users to install or run applications from 'verified sources'. 'ALL In Learning Installer.pkg' can't be opened because it is from an unidentified developer. Your security preferences allow installation of only apps from the Mac App Store and identified developers.' It's easy to allow the installation: Open Finder and go to the folder the installer was downloaded to.
Mac will now ask you to confirm. That’s it, now you should be able to install or run any app no matter where it is downloaded from. To stay safer you can also choose ‘Mac App Store and identified developers’ option, which will only allow apps from developers approved by Apple. About Gatekeeper Gatekeeper was introduced in macOS 10.7.5 and provides users more control over what they install on their Mac. They can choose to allow only apps from the Mac App Store or allow apps from the Mac App Store as well as identified developers. As of macOS High Sierra 10.13.4, right-clicking (or ^ ctrl clicking).app packages, which are not registered with Apple by an identified developer, and choosing Open won't work, so the only option left is to enable the Anywhere option under Security and Privacy in System Preferences (at least temporarily). Mac App Store: The Mac will only run apps downloaded from the Mac App Store. Mac App Store and identified developers: When you try to open a new app and it’s not on the list of identified.
By default, Gatekeeper will only open apps purchased and downloaded from the Mac App Store or from a list of “identified developers” that have been given the ok from Apple by obtaining a unique Developer ID. To install other apps, select the option to install from Anywhere.
It is important to only change Apple Gatekeeper settings to Anywhere when it is necessary to download legitimate programs. Permanently allowing applications to be downloaded from Anywhere can expose your computer to security risks from non-legitimate sources.
Always change Apple Gatekeeper settings back to Mac App Store or Mac App Store and identified developers when you are done downloading the apps you need.
Can Only Download From Identified Developers Mac Os
Note: In most cases, Gatekeeper may only need to be disabled temporarily in order to install and initially launch an application. After that, Gatekeeper can be re-enabled to only allow applications from the Mac App Store and identified developers.