MacOS in version 10.7.5 (Mountain Lion) introduced a feature named Gatekeeper [1]. The purpose of Gatekeeper is to "reduce the likelihood of inadvertently executing malware". (Ibid.) While this is a laudable goal, it does cause some difficulty for Password Gorilla users on the Mac platform. Gatekeeper determines which downloaded applications are allowed to execute based upon the applications having been cryptographically signed by a developer key issued by Apple. Unfortunately signing a MacOS application with an Apple developer key appears to require a MacOS computer, and the Password Gorilla maintainer does not have a MacOS computer.

Therefore this page exists, detailing various methods that can be used to instruct your MacOS computer to allow Password Gorilla to be launched.

The most common message reported via Github for a Gatekeeper issue is a message similar to the following when attempting to launch Gorilla:

"Password Gorilla.app" is damaged and can't be opened. You should move it to the Trash. Firefox.app downloaded this file ...

If the above message appears after downloading, verifying, and installing Password Gorilla, then this means you need to perform one of the following to indicate to your Mac that you want to allow Password Gorilla to launch:

1. Use a special launch sequence to tell MacOS that you want to allow Gorilla to launch. Follow these steps:
   1. Press and hold the 'control' key on your keyboard and then click the app.
   2. Choose 'Open' from the menu that should appear.
   The above should create an exception for Gorilla informing Gatekeeper that you with to allow it to launch. If it does not work, then try the steps in #2 below.
2. Delete the filesystem extended attribute that Gatekeeper uses to decide to block the application from launching. Follow these steps:
   1. Open MacOS's 'Finder' and navigate to the location where the Password Gorilla app. bundle is located on your disk.
   2. Open a "Terminal" from 'Finder' to the location on disk that is in 'Finder' (instructions).
   3. Type the following command exactly as shown below into the terminal window:
      xattr -d com.apple.quarantine Password\ Gorilla.app/
   The above should bypass Gatekeeper for your installed copy of Gorilla and allow you to launch Gorilla in any way that MacOS allows.
3. Disable Gatekeeper globally (this option is not recommended, but is available to you if you decide you wish to make this change).
   1. Follow the directions here and set Gatekeeper to "Anywhere" mode.
   NOTE - this option will globally disable Gatekeeper, which means you will turn off all of the malware protections that Gatekeeper offers if you choose this option. You should decide for yourself if this is what you wish to do.