Using Your iMac as a Monitor: Step-by-Step Setup Guide

Many users look to repurpose their older iMacs as secondary displays, a practice that not only extends the utility of their device but also enhances productivity. By converting an iMac into a monitor, you can enjoy a larger screen for better multitasking, more detailed graphics work, or simply a more immersive experience for media consumption.

However, it's important to note that newer iMacs, specifically those released after 2014, do not support Target Display Mode—a feature that allowed iMacs to be used as monitors for other Apple devices. This limitation necessitates alternative approaches for those with more recent iMac models who still wish to use their device as a secondary display. Thankfully, solutions such as AirPlay and various third-party applications offer viable pathways to achieve similar functionality, albeit with some differences in setup and performance. These alternatives not only circumvent the restrictions of newer models but also open up new possibilities for integration into a modern Apple ecosystem.

Using Older iMac Models as Monitors


Not all iMac models are capable of being used as monitors. This functionality, known as Target Display Mode (TDM), is restricted to certain iMac models produced between late 2009 and mid-2014. Specifically, the eligible models include:

  • 27-inch iMac models introduced in 2009 and mid-2010, which use a Mini DisplayPort for video input.
  • 27-inch iMac models from mid-2011 to mid-2014, which use a Thunderbolt connection.


To use an older iMac model as a monitor, specific hardware requirements must be met:

  • Video Cable
    Depending on the model of the iMac and the device you wish to connect, you will need either a Mini DisplayPort cable or a Thunderbolt cable. It's crucial to match the cable type with the ports available on both the primary Mac (the one you are using as the source) and the iMac you intend to use as a display.
  • Compatible Source Device
    The source Mac must also support video output through Mini DisplayPort or Thunderbolt. This includes most Mac models from the same era as the eligible iMacs.

Step-by-Step Setup

Activating Target Display Mode on your iMac is straightforward but requires that both the iMac and the source Mac are prepared and compatible. Here’s how to do it:

Connect the Cable

First, connect your source Mac to your iMac using the appropriate Mini DisplayPort or Thunderbolt cable.

Power On and Login

Ensure both Macs are turned on and logged into. It’s important that neither Mac is sleeping.

Enable Target Display Mode

On the iMac you wish to use as a display, press Command (⌘) + F2. This should instantly switch the display input to show the screen from your source Mac.


  • If pressing Command + F2 doesn’t activate Target Display Mode, ensure that the cables are securely connected and that you are using the correct port.
  • Check that both Macs are compatible with TDM and that the iMac is running an operating system that supports TDM (OS X High Sierra 10.13 or earlier).
  • Restart both devices to resolve any temporary communication issues.

By following these steps, you can effectively turn your compatible older iMac into an additional display, extending your workspace and increasing productivity. This setup is ideal for users needing more screen real estate for tasks such as video editing, graphic design, or even for better multitasking capabilities.

Using Newer iMac Models as Monitors

Newer iMac models released after 2014 do not support Target Display Mode (TDM), a feature that allowed iMacs to be used as external monitors for other Mac devices. This change primarily stems from hardware and software shifts in Apple’s product line, focusing on advancements in display technology and security that are incompatible with the requirements of TDM. The discontinuation of this feature reflects Apple's design philosophy shift towards more integrated and secure systems, which prioritizes internal display functionalities over dual-purpose use.

For users of newer iMac models seeking to extend or mirror their displays to another Mac, there are viable alternatives to Target Display Mode


A feature that allows macOS users to wirelessly transmit video, audio, and other media content to an AirPlay-compatible device, like an Apple TV or another Mac. Starting with macOS Monterey, AirPlay to Mac enables users to use their iMac as a secondary display for another Mac, offering a convenient, though sometimes less performant, solution compared to the direct cable connection of TDM.

AirPlay is compatible with a wide range of Apple devices, facilitating screen mirroring and extending capabilities across different hardware and operating systems. For using an iMac as a secondary display via AirPlay, both the source device and the iMac need to be running macOS Monterey or later versions. Here’s a breakdown of device compatibility:

  • Mac: Any Mac model introduced in 2018 or later running macOS Monterey or newer can send content via AirPlay.
  • iMac as Receiver: iMacs introduced in 2019 or later running macOS Monterey or newer can receive AirPlay signals to act as a secondary display.

Setup Guide

Setting up AirPlay to use an iMac as a secondary display involves a few straightforward steps:

Ensure Wi-Fi Connection: Both the source Mac and the iMac must be connected to the same Wi-Fi network.

Enable AirPlay Receiver on iMac:


  • Go to the Apple menu and select ‘System Preferences’.
  • Click on ‘Sharing’.
  • Check the option for ‘AirPlay Receiver’ and ensure it is turned on.

Initiate AirPlay from the Source Device:


  • Click on the AirPlay icon in the menu bar at the top of your screen. If you don’t see the icon, go to ‘System Preferences’, select ‘Displays’, and check the option ‘Show mirroring options in the menu bar when available’.
  • From the dropdown, select the iMac you want to mirror or extend your display to.

Choose Your Mode:

  • Choose to either mirror your screen or use the iMac as an extended desktop.

Adjust Display Settings if Needed

  • Once connected, you can adjust resolution and scaling by going back to ‘System Preferences’ and selecting ‘Displays’.

Use Cases and Limitations

AirPlay is ideal for situations where wireless convenience is paramount:

  • Presentations
    Easily share slides or video from a MacBook to an iMac during meetings.
  • Education
    Teachers can share content from their device to a larger screen visible to the whole classroom.
  • Creative Work
    Extend your workspace when working with graphics or video editing software.

However, there are limitations to be aware of:

  • Potential Lag
    While suitable for static images and presentations, AirPlay may experience lag during high-resolution video playback or in graphics-intensive tasks.
  • Network Dependency
    The performance of AirPlay heavily relies on the strength and stability of the Wi-Fi network. Poor network conditions can affect the smoothness and quality of the streamed content.

Third-Party Apps for Using Your iMac as a Monitor

Several software solutions enable similar functionality to what TDM offered. Apps like Luna Display or Duet Display turn an iMac into a secondary monitor using software-driven solutions that can be more flexible and powerful than AirPlay. These apps typically require installation on both the primary Mac and the iMac intended as a monitor, creating a virtual display setup that can be customized to fit different workflows and needs.

Luna Display

Luna Display turns your iMac into a secondary display that connects wirelessly or via USB. It works by plugging a small hardware piece into your main Mac and then running the Luna Display app on both the primary Mac and the iMac. This setup allows for a virtually lag-free second monitor experience and supports touchscreen inputs if you're using an iPad as the secondary display.

Duet Display

Originally designed to turn iPads into second screens for Macs, Duet Display has expanded to include support for iMacs as well. It connects your devices via USB or Wi-Fi, transforming your iMac into an extra display. Unlike Luna, Duet does not require additional hardware, making it a software-only solution.


  • Both apps provide more robust and reliable connections compared to AirPlay, especially in environments where Wi-Fi is unstable.
  • These solutions can offer additional features like touch support (iPad with Luna Display) and generally lower latency.


  • Cost
    Both Luna Display and Duet Display come with a price tag, whereas AirPlay is included with macOS.
  • Requirement of software installation and, in Luna’s case, a hardware purchase.
  • Potential compatibility issues with updates to macOS or when using very new or very old hardware models.
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