I just ran across this app from Maxivista that allows you to use your iPad as a second monitor. It's just like their other app that lets you use another computer as an additional monitor, such as a laptop. The problem is, however, it's a bit sluggish as it has to use WiFi to send what is basically a video signal.

So, are there any solutions that allow you to use an iPad as an additional screen via USB?

  • That would require some fancy footwork on the USB end of things, and I'm not clear that the current APIs allow iPad programs to get that low-level yet. You might need to look in the non-apple app stores. – Michael Kohne Aug 26 '10 at 5:05

Recently Air Display announced a beta of the Windows client so now there are two choices but it also works only over Wifi so I would imagine they would both have lag issues.

  • 1
    Air Display doesn't lag bad, but it uses compression so you get pixelation for a second on motion, but it clears quickly. I use it with my Mac but I see the Windows version is released now too. Will download it when I get home. – Jim McKeeth Sep 22 '10 at 16:44

Duet Display lets you easily turn an iPad or an iPhone into a secondary display. It works with both Mac and Windows computers.

  • 1
    Note that as of High Sierra 10.13.4, Duet (and all their competitors) doesn't work anymore. Everyone is working on a fix, but all these solutions are dead in the water for the time-being. More info: macrumors.com/2018/03/30/… – Eric Goldberg Apr 2 '18 at 22:59

Fast forward Fall 2019, macOS and iPadOS (rebranded the iOS operating system software running on iPad), now supports this natively.

The following Apple Support document talks in detail about using your iPad as your Mac's mirrored or extended display.

The key points are:

  • The feature is available on macOS Catalina 10.15 and iPadOS 13 and later.

  • The iPad can be used both as an extended display or a mirrored display.

  • The iPad can be connected to both wirelessly or via the USB cable.

  • Not all the Macs and iPad capable of running macOS Catalina and iPadOS 13 support Sidecar. List of supported devices can be found here:

  • Both the devices need to be signed in to iCloud with the same Apple ID.

You must log in to answer this question.