Fixing the 'app can't be opened' error in OS X


If you see an error message saying an 'app can't be opened' when you're trying to open or install it, it might be caused by a feature called 'Gatekeeper'.

What is Gatekeeper?


'Gatekeeper' is built into all Macs using OS X Lion onwards. It stops you from accidently installing viruses and malicious software, but it can also affect some safe software if it hasn't been approved by Apple.

If the app you're trying to install wasn't downloaded from the App Store, or isn't from a certified Apple Developer, Gatekeeper stops it being opened or installed. The fixes below show you how to override Gatekeeper and get the app installed, but you should only do this for apps you know are safe.

Override Gatekeeper


This fix applies to all versions of OS X from 10.7 Lion through to macOS 10.12 Sierra.

You can override Gatekeeper by holding down the ctrl key while clicking the app, then clicking Open on the menu that appears. This will get past Gatekeeper's protection, and open or install the app.

Disable Gatekeeper


If overriding Gatekeeper doesn't work, you'll have to briefly disable it, install yout software, then turn it back on. The steps below show you how.


Click the Apple logo in the top-left corner of the screen.


Click System Preferences.


In System Preferences, click Security & Privacy.


Click the padlock in the bottom-left corner to unlock the settings. Type your Mac password, and then click Unlock.


Change the 'Allow Apps downloaded from:' setting to Anywhere.


Open or install the app.


Once the app has opened or installed, change the 'Allow Apps downloaded from' back to App Store, or App Store and Identified Developers to turn Gatekeeper back on.

Hopefully you're sorted now, but if you need some extra help, click here to get in touch with one of our Team Knowhow experts.  

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