How to Use an iMac as an External Monitor

Do you want to use the amazing screen of your iMac as the display of your MacBook or Mac desktop? If you want to use a newer iMac with macOS Monterey, you can easily use AirPlay to project or extend the screen on your iMac. For older iMacs with High Sierra or earlier, you can use Target Display Mode to set up your iMac’s display as your Mac’s primary display. This article will give you some simple ways to use your iMac as a primary or secondary display for your Mac.

Table of Contents

Use AirPlay for Mac (macOS Monterey operating system)

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Make sure you can use your iMac as an AirPlay receiver. The macOS Monterey operating system lets you project or extend nearly any Mac display onto the new iMac.

The iMac used as an AirPlay receiver can be an iMac Pro, or an iMac released in 2019 or later. ^{[1] X Research Sources} The iMac must also have macOS Monterey or later.
The Mac sending the AirPlay signal can be any Mac or MacBook from 2011 or later. If you want to project your screen on your iMac to use as your primary display, you need Mountain Lion or later. If you want to extend the display to use your iMac as a second display, you need Mavericks or later.
You can use an older iMac as a monitor by connecting it to Target Display Mode.

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Enable AirPlay receiving on your iMac. After you turn on AirPlay receiving, your iMac displays your Mac’s choice of projection or extending the display. Here’s how to enable it:

Click the Apple menu and choose System Preferences .
Click Sharing .
Check the box next to “AirPlay Receiver” in the left pane.
Choose who can connect to this iMac using AirPlay. The best option is “Current user”, as it ensures others are not asked about projecting their screen to the iMac.

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Pin the Screen Mirroring icon to the menu bar on your sending (main) Mac. Do this on a Mac, not an iMac. This is what needs to be done when you extend the screen instead of the slide show. Proceed as follows:

Click the Apple menu and select System Preferences .
Click Dock & Menu Bar (Dock and Menu Bar).
Check the box next to “Show in Menu Bar” if it’s not already checked.
Select always (always) in the menu pane.

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Connect two Macs to Wi-Fi or with a USB-C cable. You can effectively use AirPlay wirelessly if both Macs are connected to the same Wi-Fi network. Most everyday users don’t notice the delay when using AirPlay over a Wi-Fi connection. ^{[2] X Research Source}

If you want to use your iMac as your primary display and need to do advanced video processing, you can also connect two Macs with USB-C or an AirPlay 2-enabled Thunderbpt 3 cable ^{. [3] X Research Source}

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Click the Screen Mirroring icon on the sending Mac (main machine). It’s the two overlapping squares to the left of the Bluetooth icon in the menu bar. A list of two AirPlay-compatible devices will appear with the choice to project or extend the screen.

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Select slide show or extend the screen. If you want to project your main Mac’s screen onto your iMac screen, choose Mirror . If you want to extend the display to use your iMac as a second monitor, you’ll choose Use As Separate Display .

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Click the iMac to start using it as a monitor. After you select your iMac in the list of AirPlay devices, you’ll see the main Mac screen (projected or extended) on the screen.

The iMac after becoming an AirPlay receiver will only display the main Mac’s screen.
You can end an AirPlay session on your iMac by moving your mouse to open the controls and clicking the X in the upper-left corner.

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Adjust the settings of the extended monitor. If you’re using your iMac as a second display, you’ll need to rearrange the display to suit your needs. For example, if the iMac is on the left side of the main screen, you need to move the mouse to the left to move the pointer to the iMac screen. Follow these steps to adjust the settings:

Click the Screen Mirroring icon on the menu bar.
Click Display Preferences… (Screen Preferences).
Drag the screen left or right so that the screens display in the correct position.
The white menu bar at the top of the sample screen indicates that this is the home screen. If you want to set up another display as your primary display, drag the white menu bar to it.

Use Target Display Mode on Older iMacs

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Find out if you can use Target Display Mode. Using Target Display Mode used to be the only way to use an iMac as a display for another Mac, and the feature isn’t available on the latest version of macOS. You can use Target Display Mode when:

The iMac used as the monitor can be either a 24- or 27-inch model from 2009 or 2010, or any iMac released between 2011 and mid-2014 ^{. [4] X Research Source} The iMac must have an operating system. operating macOS High Sierra or earlier .
The Mac connected to the iMac must be released in 2019 or earlier, and use the macOS Catalina operating system or earlier .

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Connect two Macs using a compatible cable. You’ll need a Thunderbpt or Thunderbpt 2 cable to connect the two Macs when using an iMac released in 2011 or later. For iMacs released in 2009 or 2010, you need a Mini DisplayPort cable.

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Sign in to the user account on the primary Mac. You can only use your iMac as your primary Mac display when your Mac is signed in to your account. The iMac cannot recognize the Mac showing the login screen.

If you want to use more than one iMac as a display, you can do so by connecting the entire iMac directly to the main Mac using a compatible cable.

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Press ⌘ Command + F2 on the iMac. Make sure you’re using the keyboard connected to the iMac, not the main Mac. After pressing this key combination, the screen of the connected Mac will show the screen of the iMac.

If the key combination doesn’t bring up the Mac’s screen, you’ll press Fn + Command + F2 .
If this doesn’t work, you can try signing out of your iMac (not the main Mac) and pressing the shortcut on the login screen.

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Use the main Mac’s keyboard and mouse while using Target Display Mode. When you use your iMac as a monitor, your regular Mac’s keyboard and mouse still control what you see on the screen.

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Press ⌘ Command + F2 on the iMac to exit Target Display Mode. When you exit Target Display Mode, what was previously opened on the iMac will appear on the screen.