That’s Duet, a free Mac app that turns an iPad into an external display for the Mac, specifically the MacBook line of notebooks where a little extra screen real estate can come in handy, and where a 12.9-inch or 9.7-inch iPad Pro can double up as a very worthy second display for your MacBook.
Let’s be honest. Many of the Mac road warrior clan carry both Mac and iPhone when traveling. Some of us even carry an iPad because it’s light, useful, easy to check-in at the airport, and handier to read on an airplane than a Mac.
Duet uses a cable to connect the iPad (or iPhone, but, like, you know, why?) to the MacBook as an external screen. Who would want that? Bear with me a moment. There’s math involved. A 13-inch MacBook Air comes with a 1266 x 768 pixel display. An iPad Air 2 comes with even more pixels at 2048 x 1536. The new iPad Pro has even more pixels than that. It’s like having a Mac notebook with dual displays.
Your iPad becomes a second, external display for your MacBook (works much the same on most recent Macs, but is perfectly matched; iPad to MacBook). The iPad looks and works as if it were an attached display. Menus work, screen pointer works, and it all works smoothly and quickly with no visible lag.
Just plug in a Lightning cable to connect iPad to Mac and you’re good to go at 60 fps. MacBook, meet high resolution external display in a smaller, convenient package. What’s not to like?
It even does Windows.
The Mac app is free, but the iOS version of Duet Display comes with a price tag so there’s no way to try the whole shebang before you buy. But if you’re interested in using an external display on your MacBook, and you have an iPad, using Duet on the Mac and Duet Display on the iPad is about as easy as it gets. The number of iTunes App Store four and five star ratings will tell you most of what you need to know.
This is one of those options that just works. And, yes, as mentioned, Duet also works on Windows PCs connected to an iPad.