Even though I own a mid-2012 MacBook Air, I use it very rarely. So far I have installed a couple of apps, most of them that I have installed are apps downloaded from the official Store. I have installed Windows 8.1 on this MacBook Air and whenever I turn on this beautiful notebook, I boot into Windows to update the antivirus and other programs. This morning, while composing 5 useful free tools for dual boot users, I decided to install NTFS Free for Mac OS X, a free program that lets you read and write to NTFS USB drive from Mac OS X. After downloading the app from developer’s page, I launched the app hoping that it would launch the setup but I got a dialog with an error saying that “NTFS free.pkg can’t be opened because it is from an unidentified developer.” As you likely know, Windows 8 and above versions of Windows also include a similar feature called SmartScreen, which tries to block lesser known programs. But in Windows 8/8.1, you can simply click More info option and then click Run anyway button to proceed installing or running the program. According to Apple knowledge base, recent versions of Mac OS X include a feature called GateKeeper, and with default settings, it allows you run apps downloaded from Mac app store and identified developers only, meaning that apps downloaded from identified developers will be blocked with default settings. Even though this is a good idea to secure your Mac, not all apps out there from unidentified developers are malicious apps and most of them are safe to install and use. In this guide, we are going to show you how you can launch an app when you see “Can’t be opened because it is from an unidentified developer” while attempting to launch an app downloaded from the web. Launch apps downloaded from unidentified developer by bypassing GateKeeper Step 1: Navigate to the Downloads folder. Step 2: Right-click on the app file that you want to launch and then click Open. That’s it! You will not see the above message now! Configure GateKeeper to allow apps downloaded from anywhere If you often install apps downloaded from the web and want to completely disable this GateKeeper feature, here is how to do it. Step 1: Open System Preferences. You can open the same by clicking the Apple logo menu and then clicking System Preferences. Step 2: Click Security and Privacy. Step 3: Switch to the General tab. Under the option titled Allow apps downloaded from, select Anywhere. If the option is not active, click on the Lock button located bottom left corner of the window to make changes. Type your account password if you’re asked to do so. Once you have selected Anywhere option, click on the lock icon again to prevent further changes. That’s it! From now onwards, you won’t see the message when you try to run apps downloaded from unidentified developers.