Is your Mac preventing you from running newly installed applications?

Apple have added a new feature in the latest version of their MacOS that may prevent you from opening or running software that you haven't bought directly from Apple.  But it's not all doom-and-gloom.  You can easily work around this.

In MacOS 10.8 (also known as "Mountain Lion") Apple added a feature called "Gatekeeper".  This feature was designed to prevent computer users from downloading and installing software from disreputable websites and unknowingly installing a virus (or Trojan Horse). It's a great idea in theory, and when we all get used to it I'm sure we'll all appreciate the benefits, but at the moment the inconvenience it causes may be it's most memorable impact.

Most people's first experience with Gatekeeper

Most people's first experience with Gatekeeper

Gatekeeper has 3 levels of "Paranoia".  You can choose whether to allow applications to run if they are downloaded from:

  1. Only the Mac App Store
  2. The Mac App Store and "allowed" developers
  3. Anywhere

This preference is set in the Security and Privacy preference pane in System Preferences

Look in System Preferences when you want to set Gatekeeper's "paranoia" level

Look in System Preferences when you want to set Gatekeeper's "paranoia" level

It should be noted that if you're upgrading your Mac from a previous version of MacOS all of the programs/applications already installed on your Mac will be allowed to run, regardless of which Gatekeeper setting you choose.  Gatekeeper only concerns itself with applications you install after upgrading.

So which level is right for you?  Unless you plan to only get your applications from the Mac App store (Microsoft Word is not available in the Mac App Store for instance) I would recommend the middle option.  This lets you install most applications from legitimate, recognised Apple developers and run them without upsetting Gatekeeper, but doesn't permit just anything to run (which would defeat the purpose of having Gatekeeper).

But what do you do if you want to run an application that Gatekeeper doesn't like?  The obvious answer is to open your Security and Privacy preferences and tell Gatekeeper to allow "applications downloaded from anywhere".  But that is overkill and onerous, since you'd have to go back and change those settings again after you've run your application. Apple has provided a much simpler way to explicitly allow an "illegal" application:

  1. Find the application that you want to open
  2. "right-click" (or "control-click") on the application's icon and you'll be presented with a list of choices.
  3. Select "Open" at the top of the list
  4. You'll be presented with the dialogue shown below
  5. Choose "Open"


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Gatekeeper will remember this choice and from then on you will be able to open the application just by double-clicking it like you do for your other applications.