Turn Your iPhone or iPad into a Secondary Display for Your Mac

Every once in a while, I run across a Mac or iOS app that knocks my socks off. Today, I'm going to share one of those apps with you.

Sitting on my desk in my home office is my 15" MacBook Pro with a secondary display next to it (Apple Thunderbolt Display). It's a great setup. I find myself using both displays constantly, moving apps back and forth to match my workflow. When I am working on the go without my secondary display, it tends to slow me down a bit (the lack of screen real estate is surprisingly noticeable). With this app recommendation, you can turn your iPad or iPhone (yes, iPhone!) into a portable secondary display for your Mac. Fasten your seatbelt!

The app is called Duet Display, and was developed by a group of ex-Apple Engineers (so you can expect top-quality work). Before I say too much more about the app and how it works, let's first talk about the requirements:

  • Mac: any Mac running OS 10.9 or later
  • iPhone: any iPhone running iOS 7 or later
  • iPad: any iPad running iOS 7 or later

That's it! Those are the requirements. Simple enough. Now, let's talk about how it works.

In order to use Duet, you need to download, install and run the Mac app. This part is free.

Next, you need to purchase and download Duet Display from the App Store. At the time of this post, the app costs $15.99 (totally worth it for road warriors). If you purchase the app on one device, it's free to download on other devices you own (buy once, use many).

Now that you have both apps installed, let's use it! Simply use your Apple sync cable to connect your iPhone or iPad to your Mac. Once connected, run the Duet Display app on your iOS device. Your Mac will detect the iOS device as a secondary display, and automatically adjust the resolution to match. This process takes only a couple seconds, and you will see some screen flickering. This is completely normal. Once it has adjusted, your secondary display is ready to be used as such. Here's a screenshot of my iPad being used as a secondary display.

Believe it or not, there is very little lag in video performance. So little, in fact, that most people won't even notice it. It's even good enough to play HD video. If you want to adjust the logical position of the secondary display, you can go into System Preferences > Displays and drag the secondary display to the left or right side of the primary display (or even above or below). Again, OS X doesn't care that it's an iOS device... it treats it like any other monitor.

While being used as a secondary display for your Mac, you can still use your iOS device as an iOS device. Simply press the Home button to access other apps. When you're ready to use it as a secondary display again, return to the Duet Display app, and it will resume from where it left off.

When you're ready to disconnect your iPhone or iPad as a secondary display, all you have to do is unplug the sync cable, and your Mac will automatically adjust to a single-display environment.

Posted on November 24, 2015 and filed under Design, How To, iOS, iPad, iPhone, Mac, Opinion.