While working on desktops or laptops, it’s useful to have a second display handy. Another monitor can easily be plugged in, but why not use the screens you already have instead of going off and purchasing another one? With a little bit of effort, the iPad, iPhone, and iPod Touch can be turned into a second screen for your Mac or Windows computer. This can be used in two ways: using the iOS device as a true second display, or mirroring the content of your main display. In this post, you’ll learn how to accomplish both.

Air Display

Air Display is actually two separate applications: one running in Windows or OS X, and an app running in iOS. First off, download and install the client on your computer. Next, you’ll need to buy the iOS app for $9.99 on the App Store. Once both are running, connect both to the same WiFi network, and then follow the on-screen instructions to make sure they are talking to each other.

Once they’re connected on OS X, you can configure them even further. Launch System Preferences, and select the Displays section. On the iOS device, you’ll be able to configure your resolution. Specifically, devices with Retina displays can enable High Dots Per Inch (HiDPI) mode that draws windows as if the resolution was a quarter the size, but with the full detail that your screen allows. Sadly, the Windows version doesn’t support the high resolution mode properly just yet, but the developer promises this will be added in a future update.

On your main display in Mac OS X, you can now adjust where the second screen sits in relation to your main screen by switching to the “Arrangement” tab. In Windows, you need to open the system tray icon and select “Display Arrangement.” In OS X, this screen also displays a toggle called “Mirror Displays.” This will turn your iOS device into a duplicate of your main screen. This is useful if you’re trying to show someone a website or a photo, and you don’t want to huddle in front of your computer. If you want to enable mirroring on Windows, simple click the system tray icon, and navigate to “Options,” and click “Enable Mirror Mode.”

VNC

If all you’re looking for is display mirroring and control of your main screen on your iOS device, Virtual Network Computing (VNC) might be the best option for you. This is built right into Mac OS X, but Windows users will need something like TightVNC which is available for free. Not only will VNC mirror your screen, but it also allows you to control the computer remotely. Seeing what’s on your screen is nice, but being able to manipulate your computer when you’re not at your desk is even better.

To turn it on in OS X, go into System Preferences under the Sharing section, and check the Screen Sharing toggle. Whichever way you plan on enabling VNC on your computer, make note of your local IP or Bonjour address displayed by your software.

Next, you’re going to need a VNC client for your iOS device. Some clients are available for free like Mocha VNC Lite, but apps like iTeleport ($4.99) and Mocha VNC ($5.99) are more feature-rich. Once you have one installed, input your computer’s IP or Bonjour address into the configuration, and you’re good to go.

These require a bit of effort to set up, but it certainly worth the hassle. You’ll be glad to have went jumped through these hoops when you need that display at your desk, or if you want to turn off that download without getting out of bed.