How to Use an iMac as an External Monitor

Use AirPlay for Mac (macOS Monterey operating system)

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. 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'll 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.

Enable AirPlay receiving on your iMac. After you enable AirPlay reception, 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 choice is "Current user", as this is an option that ensures others are not asked about projecting their screen to the iMac.

Pin the Screen Mirroring icon to the menu bar on the sending signal (main machine). 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.

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.

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 a USB-C or Thunderbolt 3 cable that supports AirPlay 2.

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.

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 .

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 that becomes 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.

Adjust the settings of the extended display. 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

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 display can be a 24- or 27-inch model from 2009 or 2010, or any iMac released between 2011 and mid-2014. The iMac must have 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 .

Connect two Macs using a compatible cable. You'll need a Thunderbolt or Thunderbolt 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.

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 multiple iMacs as a display, you can do so by connecting the entire iMac directly to the main Mac using a compatible cable.

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.

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.

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.

Another choice

Duet Display is a third-party option that lets you use your iMac as a display. This is premium software that you can install on your iMac, and the main Mac allows you to use your iMac as a display. You need a paid subscription to Duet Air to use this feature, or opt for a free trial.

Try Luna Display to use any iMac as a primary or secondary display. Luna Display improves Target Display Mode by allowing you to use any iMac (even newer) as a second display. To use Luna Display, you need to purchase a special USB-C or Mini DisplayPort connector to connect to the main Mac, and install Luna's software on both systems.

Use the new TV as a screen. If you need a bigger screen, you can connect your Mac to a TV and use it as a display. If you have an HDTV with a Thunderbolt, Mini DisplayPort, or HDMI port, you can also play audio on your Mac through the TV.

Project your screen to your TV using AirPlay. If you have a TV that supports AirPlay 2 — or even a streaming device like a newer Apple TV or Roku — you can use your TV as a display for your Mac. Simply turn on your AirPlay-enabled TV or streaming device, open Control Center on your Mac, and click the Screen Mirroring option.