Fix the “App can’t be opened because it is from an unidentified developer” Error in Mac OS X

Mac OS X defaults to preventing applications from unidentified developers or sources from being launched. You’ll discover the message in Mac OS when you try to launch a Mac app that didn’t come from a verified source or from the Mac App Store, and you’ll get an alert dialog that says “[App name] can’t be opened because it is from an unidentified developer”.

This security feature is called GateKeeper, and it doesn’t mean you can’t run those unverified apps on the Mac, you just have to either temporarily skirt the security blanket of GateKeeper, or turn off the app limitations entirely.

How to Temporarily Get Around “App Can’t Be Opened” Gatekeeper Alert Message on Mac

Temporarily bypassing Gatekeeper to skirt around the “unidentified developer” error message is probably the best option for most Mac users, since it maintains some security systemwide and instead simply allows the specific app to open:

1. Right-click (or control-click) the application in question and choose “Open”
2. Click the “Open” button at the next dialog warning to launch the app anyway

You can do this with any third party app that gives you this warning dialog and open it anyway.

If you get tired of constantly right-clicking apps to open them, return to pre-Mountain Lion levels of app security by turning off Gatekeepers app verification completely.

Disable GateKeeper’s Unidentified App Developer Prevention Completely

This is generally best for advanced users who know what apps to trust and not to trust:

1. Launch System Preferences from the Apple  menu
2. Choose “Security & Privacy” and then click the “General” tab, followed by clicking the lock icon in the corner to unlock the settings
3. Look for “Allow applications downloaded from:” and choose “Anywhere” *



4. Accept the security warning and allow
5. You can now launch any app from any location or developer

* Newer versions of macOS can allow apps from anywhere with these instructions if the option is not immediately available

This is the same in all versions of Mac OS X with Gatekeeper support, including MacOS Mojave, MacOS High Sierra, macOS Sierra, El Capitan, OS X Yosemite 10.10.x, OS X Mavericks, 10.9.x, and Mountain Lion 10.8.x, where the feature was first introduced.