How to Use Your iMac as a Second Display for Another Computer

You can use an iMac as an external monitor, but only with specific Mac models and only in one direction

An iMac can display video from another Mac, but the feature is called Target Display Mode and it works only on iMacs made between 2006 and 2014. If your iMac is newer than 2014, this option does not exist — Apple removed the feature. If you have an older iMac that supports it, you can connect it to another Mac with a Thunderbolt or Mini DisplayPort cable and use the iMac's screen as a second display.

The limitation matters: you cannot use an iMac as a monitor for a Windows PC, a laptop from another brand, or even a newer Mac. You also cannot send video from the iMac to another display — the feature only works one way, with the iMac receiving the signal. If you need a second display for a newer iMac or a different type of computer, you will need to buy an actual external monitor instead.

Key Takeaways

Target Display Mode works only on iMacs manufactured between 2006 and 2014; newer iMacs do not support this feature.
You need a Thunderbolt or Mini DisplayPort cable to connect the iMac to another Mac, and both computers must be powered on.
The iMac acts as a passive display only — you cannot use it as a monitor for Windows PCs or non-Apple devices.
If your iMac is too new or you need to connect a different type of computer, a standard external monitor is your only option.

Check whether your iMac supports Target Display Mode

The first step is confirming your iMac's manufacturing year. Click the Apple menu in the top-left corner, select About This Mac, and look at the line that says "Model Identifier" or the year listed under the iMac name. If the iMac was made in 2015 or later, Target Display Mode is not available, and you cannot use it as a monitor.

If your iMac is from 2014 or earlier, check which ports it has on the back. Look for a Thunderbolt port (a small rectangular port with a lightning bolt symbol) or a Mini DisplayPort (similar shape, no lightning bolt). iMacs from 2006 to 2009 used Mini DisplayPort; iMacs from 2010 to 2014 used Thunderbolt. If you see USB ports but no Thunderbolt or Mini DisplayPort, your iMac does not support the feature.

Connect the iMac to another Mac using the correct cable

You will need a cable that matches both computers' ports. If both Macs have Thunderbolt ports, use a Thunderbolt cable. If the iMac has Mini DisplayPort and the other Mac has Thunderbolt, you can use a Thunderbolt cable — Thunderbolt is backward-compatible with Mini DisplayPort. If the other Mac has only USB-C or Thunderbolt 3 (a smaller, oval port), you will need a USB-C to Thunderbolt adapter or a USB-C to Mini DisplayPort adapter, depending on which iMac you have.

Connect one end of the cable to the Thunderbolt or Mini DisplayPort on the back of the iMac, and the other end to the matching port on the other Mac. Both computers must be powered on and awake — if either one is in sleep mode, the connection will not work. You may need to wake the sleeping Mac by moving its mouse or pressing a key.

set up Target Display Mode on the iMac

Once the cable is connected and both Macs are awake, press and hold the Command + F2 keys on the iMac's keyboard (or the keyboard connected to the iMac). The iMac's screen should go blank for a moment, then display the desktop of the other Mac. The iMac is now acting as an external monitor.

If Command + F2 does not work, try Command + Fn + F2 instead — some iMac keyboards require the Fn key. If neither combination works, check that the cable is fully inserted into both ports and that both Macs are awake. Restart both computers and try again.

Use the iMac's keyboard, trackpad, and speakers while in Target Display Mode

When Target Display Mode is active, the iMac's keyboard and trackpad control the other Mac. You can type, click, and navigate as if you were using the other Mac directly. The iMac's built-in speakers will play audio from the other Mac, so you do not need external speakers unless you want louder sound.

The iMac's own operating system is not running — it is purely displaying and receiving input from the other Mac. You cannot switch between the iMac's own desktop and the other Mac's desktop while in this mode. To return to the iMac's own screen, press Command + F2 again, and the iMac will restart its own operating system.

Troubleshoot connection problems

If the iMac screen stays black or shows a "no signal" message after you press Command + F2, first check that the cable is seated firmly in both ports. Disconnect it, wait five seconds, and reconnect. If that does not work, restart both Macs completely — do not just wake them from sleep.

If you are using an adapter (for example, USB-C to Thunderbolt), try connecting the cable directly without the adapter if possible. Some adapters are not compatible with Target Display Mode. If the iMac is very old (2006 to 2009), the other Mac may need to be a similar age or older — very new Macs sometimes do not work with older iMacs in Target Display Mode.

If Target Display Mode still does not set up, open System Preferences on the iMac (not the other Mac), go to Energy Saver, and make sure "Allow your Mac to be used as a display" is checked. On some older iMacs, this setting must be enabled before Target Display Mode will work.

Consider alternatives if your iMac is too new or the connection does not work

If your iMac is from 2015 or later, or if you need to connect a Windows PC or non-Apple device, Target Display Mode is not an option. In these cases, you will need to buy a separate external monitor. Look for a monitor with the same type of port as your computer — USB-C, Thunderbolt 3, HDMI, or DisplayPort — and check the monitor's resolution and size to match your needs.

Another option is to use software-based screen sharing instead of a physical display. Applications like Apple Remote Desktop, TeamViewer, or Chrome Remote Desktop let you view and control another Mac or PC from your iMac over a network, though this is slower than a direct cable connection and requires both computers to be on the same Wi-Fi network or connected to the internet.

Frequently Asked Questions

Can I use a newer iMac as a monitor for an older Mac?

No. Target Display Mode only works when the iMac is the display — the iMac receives video from another computer. Newer iMacs (2015 and later) do not support this feature at all, so they cannot be used as monitors for any other computer.

What if I have a 2015 or newer iMac and need a second display?

You will need to buy an external monitor. Look for one with USB-C or Thunderbolt 3 if your iMac has those ports, as they can also charge your Mac while displaying video. Standard HDMI or DisplayPort monitors work too, but you will need an adapter.

Can I use Target Display Mode with a MacBook or Mac mini?

No. Only iMacs support Target Display Mode. MacBooks and Mac minis cannot be used as external monitors, even if they are old enough to have Thunderbolt ports. You will need a separate external display for these computers.

Will Target Display Mode work over Wi-Fi or wirelessly?

No. Target Display Mode requires a direct physical cable connection between the two Macs. The cable must be Thunderbolt or Mini DisplayPort, depending on which iMac you have. Wireless connections do not support this feature.

Can I use an iMac as a monitor for a Windows PC?

No. Target Display Mode only works between two Macs. Windows PCs cannot connect to an iMac's display, even with adapters or special software. You will need a standard external monitor designed for Windows computers.

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