How to Use iMac as Monitor for MacBook with AirPlay
Repurposing an older iMac as a secondary display for your MacBook is a brilliant way to extend your screen real estate without spending money on a new monitor. However, Apple’s ecosystem has evolved, and the method you use depends entirely on the age and model of your devices. The process has shifted from a simple cable connection known as Target Display Mode to a wireless solution called AirPlay to Mac, and for some setups, third party network tools like Luna Display are the only bridge left. Understanding these distinctions is critical to avoiding frustration and purchasing the wrong cables.
Method 1: AirPlay to Mac (For Modern Macs) For Macs running macOS Monterey or later, Apple introduced "AirPlay to Mac," which allows you to wirelessly extend or mirror your MacBook's screen to a compatible iMac.
1. Check Compatibility: Ensure both devices are logged into the same iCloud account and are on the same Wi Fi network.
2. Activate: On your MacBook, open the Control Center (top right menu bar), click Screen Mirroring, and select your iMac from the list.
3. Optimize: If you notice lag, you can use a USB C or Thunderbolt cable to connect the two devices directly. This wired connection still uses the AirPlay protocol but offers significantly lower latency and higher stability than Wi Fi.
Method 2: Target Display Mode (For Legacy iMacs) This is the "classic" hardwired method, but it is highly restrictive. It only works if your iMac is a specific model released between 2009 and mid 2014.
1. Identify Your iMac:
o 2009 2010 models (27 inch): Requires a Mini DisplayPort cable.
o 2011 2014 models: Requires a Thunderbolt cable (and a Thunderbolt 2 adapter if connecting to a newer USB C MacBook).
2. The Connection: Plug the cable into both Macs. Ensure the iMac is booted up and logged in.
3. The Shortcut: Press Command + F2 on the iMac's keyboard. This toggles the display input, effectively turning the computer into a dumb monitor.
4. Limitations: This feature was removed in Late 2014 with the introduction of 5K Retina displays, as the bandwidth required was too high for simple cables at the time.
Method 3: Network Sharing & Third Party Tools If your hardware falls into the "gap years" (e.g., a Late 2015 iMac) where neither Target Display Mode nor AirPlay to Mac is supported, you aren't out of luck.
· Screen Sharing: Built into macOS, this allows you to view and control another Mac, though it's not a true extended monitor. Go to System Settings > General > Sharing and enable "Screen Sharing."
· Luna Display / Duet Display: These are third party hardware/software solutions that trick your Mac into thinking a secondary display is attached via USB or Wi Fi. While they cost money, they are the only reliable way to achieve true dual screen functionality on incompatible hardware.