Use iMac as Monitor

To use an iMac as a monitor or external display for another computer, you can utilize the so-called Target Display Mode. However, this only works with certain iMac models and macOS versions. Here's a summary of the steps and requirements:

Requirements:

1. iMac model: Target Display Mode only works with iMacs manufactured between 2009 and mid-2014 and running up to the High Sierra operating system. The display mode no longer works with newer Mac OS X versions.
   
   
   • Compatible models:
     • iMac 27" Late 2009 to Mid 2014
     • iMac 21.5" and 27" Mid 2011 to Mid 2014
       
       
2. Mac computer: The other computer that wants to use the iMac as a monitor must be a Mac with a Mini DisplayPort or Thunderbolt port.
3. Cable: You need either a Mini DisplayPort cable or a Thunderbolt cable, depending on the ports of the devices involved.

Steps to use the iMac as a monitor:

1. Establish connection: Connect the Mini DisplayPort or Thunderbolt cable between the iMac and the other Mac computer.
2. Activate Target Display Mode: Start both devices and log in to the iMac that will be used as a display. Press the key combination Cmd + F2 (or Cmd + Fn + F2 on some keyboards) on the iMac. This activates Target Display Mode, and the iMac functions as an external monitor.
3. Usage: The iMac now displays the screen of the connected Mac computer. You can use it like a regular external monitor.
4. Exit Target Display Mode: To exit Target Display Mode, press Cmd + F2 again or disconnect the cable.

Limitations:

• Newer iMac models (from 2015) and current macOS versions no longer support Target Display Mode.
• The iMac can only be used as a monitor for a Mac, not for a Windows PC or other devices.

Besides Target Display Mode, there is another way to use an iMac as a monitor: AirPlay. This method works with newer iMac models and allows you to wirelessly display the screen of another Mac on the iMac.

Using the iMac as a monitor via AirPlay:

Requirements:

1. iMac model: AirPlay works on iMacs from 2019 with macOS Monterey or newer.
2. Second Mac: The Mac from which you want to mirror the screen to the iMac should also be using macOS Monterey or newer.
3. Shared network: Both devices must be on the same Wi-Fi network.
4. AirPlay-capable Macs: AirPlay works on Macs from 2018 or newer.

Steps to use AirPlay:

1. Activate screen sharing via AirPlay:

   • On the Mac from which you want to share the screen, open the Control Center (top right in the menu bar) and select Screen Mirroring.
   • Now select the iMac from the list of available devices.

2. Use iMac as AirPlay target:

   • The iMac will function as an external monitor and display the screen of the other Mac. You can now use the iMac like a regular second monitor.
   • On the iMac, the display will mirror, or you can use it as an extended display in the System Preferences under Displays.

3. End the AirPlay connection.:

   • To end the AirPlay transmission, go back to the Control Center on the sending Mac and turn off screen sharing.

Advantages of AirPlay:

• Wireless: Unlike Target Display Mode, you don't need any physical cables.
• Extended or Mirrored Mode: You can choose whether the iMac is used as an extended screen or as a mirror of your main screen.
• Current Support: AirPlay also works with newer iMacs and macOS versions that no longer support Target Display Mode.

Limitations:

• Slight Latency: Since AirPlay works wirelessly, there may be minimal delay in display, making it less ideal for very fast, interactive applications (such as gaming or video editing).
• Device Compatibility: Only newer iMacs and Macs from 2018 onward support this feature.

Summary:

With AirPlay, you have a modern, wireless method to use your iMac as an external monitor, which is especially suitable for newer devices. This complements the classic Target Display Mode and offers a simple solution for wireless working with multiple monitors.