sodcalculator

10 Tech How-To

Using an iMac as a PC Monitor: Step-by-Step

Guide 10-8843 · Updated · Step by step

This guide shows you how to use an iMac as an external monitor for a Windows PC or laptop. It covers both modern iMacs (with Target Display Mode) and older models that need a different approach, plus what to do when the feature isn’t available.

What You’ll Need

  • An iMac that supports Target Display Mode (see Step 1 for the list)
  • A compatible video cable: Mini DisplayPort or Thunderbolt (depending on your iMac and PC)
  • If using a PC with HDMI only, you’ll need an adapter (e.g., Mini DisplayPort to HDMI or USB-C to HDMI, depending on the iMac’s ports)
  • For older iMacs without Target Display Mode, a video capture card (e.g., USB 3.0 HDMI capture device) and HDMI cable

Step-by-Step

  1. Check if your iMac supports Target Display Mode. Target Display Mode works on iMacs from 2009 to 2014. Specifically, 27-inch models from late 2009 to late 2013, and 21.5-inch models from late 2011 to mid-2014. If you have a 2015 or later iMac, Target Display Mode is not supported (see Troubleshooting).
  2. Identify the video input port on your iMac. On supported models, the port is either Mini DisplayPort (2009-2011) or Thunderbolt (2011-2014). Both look the same, but Thunderbolt ports are faster. Check the back of your iMac for the port icon.
  3. Check your PC’s video output. Most PCs have HDMI, DisplayPort, or USB-C. You’ll need a cable or adapter that connects your PC’s output to the iMac’s Mini DisplayPort/Thunderbolt input. For example, if your PC has HDMI and your iMac has Mini DisplayPort, you need a Mini DisplayPort to HDMI cable or an adapter.
  4. Connect the cable. Plug one end into your PC’s video output and the other into the iMac’s Mini DisplayPort/Thunderbolt port. If using an adapter, connect the adapter to the iMac, then the cable to the adapter.
  5. Turn on the iMac. If it’s already on, make sure it’s running macOS. Target Display Mode requires the iMac to be booted into macOS (not Windows via Boot Camp).
  6. Enter Target Display Mode. Press Command (⌘) + F2 on the iMac’s keyboard. If that doesn’t work, try Command + Fn + F2 (on some keyboards). The screen should go black and then display your PC’s output.
  7. If the iMac doesn’t detect the signal, try pressing Command + F2 again. Also, ensure the PC is sending a signal (check its display settings).
  8. To exit Target Display Mode, press Command + F2 again. The iMac will return to macOS.
  9. For iMacs without Target Display Mode (2015 and later): You cannot use them as a monitor directly. Instead, you’ll need a video capture card. Connect the capture card to your PC via USB, then connect the PC’s HDMI output to the capture card’s input. Open the capture card’s software on the iMac to view the PC’s screen. Note: this adds slight lag and may not be ideal for gaming or video editing.

Common Mistakes

  • Using the wrong cable: Many people try to connect a PC’s HDMI directly to an iMac’s Thunderbolt port with a simple HDMI-to-Thunderbolt cable, which doesn’t exist. You need an adapter that converts the signal, not just a cable with different ends.
  • Forgetting to press Command+F2: The iMac won’t automatically switch to Target Display Mode when you plug in a cable. You must press the shortcut.
  • Using a 2015+ iMac and expecting Target Display Mode: This feature was removed, so no amount of cable swapping will make it work. You’ll need the capture card workaround.
  • PC is set to mirror or extend incorrectly: If the PC screen doesn’t appear, check your PC’s display settings (Windows key + P) and select “Duplicate” or “Extend” to send a signal to the iMac.

Tips

  • Use the iMac’s keyboard for the shortcut: If you have a Windows keyboard connected to the iMac, the Windows key may work as Command. Try Windows + F2.
  • Keep the iMac plugged in: Target Display Mode does not charge the iMac’s battery (if it’s a laptop–but iMacs are desktops, so it’s always plugged in).
  • Adjust resolution: The iMac will display at its native resolution (e.g., 2560×1440 for 27-inch models). Set your PC’s output to match that resolution for the sharpest image.
  • Use a Thunderbolt cable for best performance: If your iMac has Thunderbolt, a Thunderbolt cable ensures proper signal integrity, though a Mini DisplayPort cable also works.
  • Exit Target Display Mode before unplugging: Always press Command+F2 to exit, then unplug the cable to avoid any glitches.

Troubleshooting

  • Command+F2 doesn’t work: Make sure the iMac is running macOS, not Windows. Also, check if the keyboard is working (try Caps Lock). If you have a third-party keyboard, try the built-in one.
  • Screen stays black: Check the cable connections. Try a different cable or adapter. Ensure the PC is on and sending a signal (try a different monitor to confirm).
  • PC shows “No signal”: The iMac may not be in Target Display Mode. Press Command+F2 again. If that fails, restart the iMac and try again.
  • Image is blurry or stretched: Set your PC’s resolution to match the iMac’s native resolution. For 27-inch iMacs, that’s usually 2560×1440; for 21.5-inch, 1920×1080.
  • iMac is 2015 or later: Target Display Mode is not supported. Use a capture card (as described in Step 9). Some older iMacs (pre-2009) also lack this feature.

Frequently Asked Questions

Can I use a 2015 iMac as a monitor?

No, Target Display Mode was removed after 2014. You can use a video capture card, but it’s not a direct connection and adds lag.

Does Target Display Mode work with Windows via Boot Camp?

No, the iMac must be booted into macOS. If you’re in Windows, restart and hold Option to select macOS.

Can I use a PC with a DisplayPort output?

Yes, if your PC has DisplayPort, you can use a DisplayPort to Mini DisplayPort cable (or adapter).

Will the iMac’s speakers work?

No, Target Display Mode only passes video. Audio from the PC will come from the PC’s speakers or headphones.

Can I use a 21.5-inch iMac as a monitor?

Yes, if it’s from 2011 to 2014 and has Target Display Mode. Earlier 21.5-inch models (2009-2010) do not support it.

What if I have an iMac with a 5K Retina display?

Those are 2014 and later, so they don’t support Target Display Mode. Use a capture card or a separate monitor.

Related

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

More in this bed

The whole Tech How-To bed →