This ex-Apple engineer's new app turns your iPad into a second display for your Mac or PC

Duet Display is an app designed to get you some extra use out of your iPad.

Instead of letting your iPad collect dust when you're not using it, Duet Display turns your iPad into a second display for your computer, using the iPad's charging cord to connect to your computer.

Duet Display originally launched for Mac, but on Tuesday Duet Display for PC arrived, allowing Windows users the chance to use their iPad as a second screen for their computer.

The app was created by Rahul Dewan, an engineer who worked at Apple for three years on both the iPad and iMac before creating Duet Display.

"A second display can increase productivity up to 48%," Dewan told Business Insider when the app first launched. "If you have an iPad, you already have that second screen. With Duet, you can finally use it. Otherwise, your $700 device is just sitting there."

In addition to giving you extra screen real estate (which is great for musicians, designers, and photo and video editors), Duet Display also takes advantage of the iPad's touch capabilities, allowing you to tap and scroll through whatever you choose to drag over to the second display.

While other apps like Air Display already exist that will turn your iPad into a second display, those apps usually connect your iPad to your Mac or PC using wi-fi, which can lead to a lot of lag. Duet Display, on the other hand, has zero lag, and it also offers a true Retina resolution that takes full advantage of the iPad's HD display.

Duet Display also offers energy saving options for people using older computers that aren't as powerful. You can choose between regular and Retina resolution (you'll need a newer computer with a bit of power behind it for Retina mode to work seamlessly), and you can also switch between a 30 Hz and 60 Hz refresh rate.

Setting up Duet Display is a cinch, and it works for any Macs running OSX 10.9 and up, and PCs running Windows 7 or Windows 8.

First, you'll need to download the app on your iPad. Next, head on over the official website and download either Duet Display for Mac or Duet Display for PC depending on your computer and install the software.

Finally, just restart your computer, and you're ready to go.

In use, Duet Display performed exactly how I'd like it to. I could drag a webpage with my Twitter feed or Slack chat over to my iPad's screen, and I'm a big fan of how you can tap fullscreen to have whatever window you're displaying expand to fill the entire screen. YouTube videos played back smoothly, and I even played a game of Hearthstone just to see if it worked for games (it does, but most of the time it makes more sense to just game on your primary display). Duet Display also works in either portrait or landscape mode.

Most importantly, Duet Display is the first app that actually turns your iPad into a second display I'd actually like to use. As someone who has tried Air Display and uninstalled it shortly afterward, frustrated, I can honestly say this is the only option that's worth it.

You can download Duet Display by clicking here.