If you see the error message, "Firefox.app can't be opened because the identity of the developer cannot be confirmed" when you try to open it, here are a few things to try.
Try this first:
- Hold down the Control key while clicking on the Firefox icon in the Dock or on the Firefox application file in a Finder window.
- Click Open in the context menu.
- Click Open in the following dialog window.
If that doesn't resolve the issue, try this next:
- Click on the Apple icon at the top left corner of your screen and open System Preferences.
- Click on Security & Privacy, then select the General tab.
- You will see a message stating that the Firefox.app was blocked. Click on Open Anyway.