How to use your iPad or iPhone as a second monitor
Mac Tip #493, 06 July 2011

If you need just a little bit of extra screen space but don’t want to invest in a whole extra monitor here’s how to press your iPad, iPhone or iPod touch into service. It’s actually very easy — with the right, low cost software, and provided you’re using a WiFi network.

I’ve already set up my iPad, so in this Tip I’ll set up my iPhone.

This works for Windows users too, but I haven’t tried that. Tell us in the Comments if you’re using this technique with Windows and your iOS device.

Air Display apps make it work

To share out your Mac’s screen you need Air Display. The software comes in 2 parts: free server software for Mac or Windows and a low-cost app for your iOS device (iPad, iPhone or iPod touch).

The Air Display Settings screen.

Install the server software

Download the free Air Display server software and install it on your Mac. It installs as a System Preference pane. To set up the software:

1. Go to System Preferences.
2. Look on the bottom line under Other and click on Air Display. The Air Display settings appear.
3. The first and most important thing is to turn the server on. To do that click beside On on the left-hand side. You are now ready to connect to your Mac.
4. You may also wish to set the other Settings. When you’re ready, click the Settings tab and choose how you want Air Display to behave.

Install the app on your iPad

1. Go to the App Store and find the Air Display app. Buy and install it on your device.
2. Find the app on your device’s screen and tap to open it.

Now you’re ready to Connect the iPad or other device to the Mac.

Connect to an iOS device.

Connect the iPad to the Mac

1. Go back to Air Display in the Mac’s System Preferences and look on the Connect tab.
2. Click on the Device dropdown menu and choose the device you want to connect to. My iPad’s named Acrux, while my iPhone’s called Spiral. The screenshot shows me connecting to Spiral.

Once you select a device you’ll start to see the Mac’s screen on that device.

Mirror the screen.

Mirror the screen

If you’re not used to using an additional display with your Mac you may find that strange things happen. This will be because the screen on an iOS device is a different size from the screen on your Mac.

You may find that everything from your Mac’s screen is mirrored on your iPad. That means both screens show exactly the same thing. This is very handy if you’re giving a presentation and have a projector attached to display your screen to an audience.

Some less capable Macs only support mirroring.

If two differently sized screens both show the same thing then windows may change size and move position.

Extend the screen

If you have 2 screens and a Mac that supports it you can use a second monitor to show something different from what you see on the main screen. This is how I use my iPad, so I can show a few windows related to my dictation software on my iPad while I mainly work on the Mac’s screen.

Arrange the screens.

Arrange the screens

Any time you have an additional monitor attached you can choose how to arrange the screens: mirrored or side by side (or above and below). To set up additional displays:

1. Open System Preferences and click on Displays in the second row. The Displays pane opens.
2. Click on the Arrangement tab. The tab shows an image of all the monitors attached to your Mac.
3. Check or uncheck the Mirror Displays checkbox in the lower left part of the window. Your screens may change in various ways, depending on your selection. You may find windows move, fonts look bigger or smaller, and the desktop picture may alter on the iOS device’s screen.
4. Each monitor is represented by a ‘window’ icon in the middle of the window. Drag the icons around to arrange them as you like. Notice that if you click and hold on an icon a solid red outline appears around both the icon and the screen it represents, helping you to identify which is which.
5. Close System Preferences when things are arranged to your taste.

The window is partly on the main screen …   … and partly on the iPhone screen.

Move windows to the second screen

I prefer to put my iPad to the top right of my Mac’s screen. To move a window to the iPad’s screen I just drag the title bar of that window to the right of the Mac’s screen and then keep on dragging. The window shows up on the iPad’s screen. Both screens now act as though they are a single, wider, screen.

Turn Air Display Server off

When you’re finished using your iOS device as a second monitor go back to System Preferences — Air Display and set the Server to Off.

Extra Tips

In the Air Display settings check the box to Enable touch. That allows you to touch your iOS device’s screen to make selections, check and uncheck checkboxes, select on-screen menus and so on — just like using a mouse.

In the Air Display settings check the box to Show Air Display in menu bar. That adds an icon to your menu bar that makes it easy to access the preferences, connect to devices and so on.

With the secondary monitor connected, call up the System Preferences Desktop & Screensaver preferences pane. Each screen will show its own window where you can select background patterns for each device.

MacBook Pro and iPad side by side on my makeshift standing desk.

The iPad’s a handy second screen for reference

When all I want to do is get a few palettes or information windows off my main screen so I can easily refer to them this is a superb way to do it. It saves me having to buy and place a whole second monitor.

I wouldn’t really want to try to work on the iPad’s screen using this technique, but it’s a wonderful way to display extra information. The few dollars I spent on the Air Display software have been well worth it.

Update Saturday, 16 July 2011: Jeff Carlson has written a column in The Seattle Times about using Air Display with his Macs — App extends desktop wirelessly:

It seems extremely odd at first, but with an iPad in a stand and Air Display running, there’s plenty of screen real estate to hold one or two applications’ windows on the iPad. Who said an external display needed to be a monitor, after all?

Tell us about your experiences with additional monitors in the Comments at MacTips.info. Could you write a guest MacTip? If so, contact Miraz.

Credit where it’s due

This Tip was written by Miraz Jordan, http://mactips.info, and is available under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.