Use an iMac as a monitor for your MacBook

Second Display is an app on both Macs. It gives your MacBook an extra display, as if you had plugged in a monitor, and shows it on the iMac. Windows and the pointer move onto it like onto any other display. Apple’s Target Display Mode can’t do this with an Apple silicon MacBook.

What you need

Mac	Needs
MacBook	macOS 14 Sonoma or later, and a Thunderbolt port (⚡︎) for the sharpest picture.
iMac	A model from late 2015 or later with macOS 12.3 Monterey or later. No account and no Screen Recording permission.
Between them	A Thunderbolt cable, or both Macs on the same Wi‑Fi or Ethernet network.

Not sure your MacBook runs macOS 14? Apple lists the models: Apple: Macs that run macOS Sonoma. What you need

Which cable for which iMac

• iMac from 2017 on, and iMac Pro. These have Thunderbolt 3 ports, the same shape as your MacBook’s. Connect them directly with a Thunderbolt cable. The 24‑inch iMac with Apple silicon connects the same way.
• iMac from late 2015. Its ports are Thunderbolt 2, so a USB‑C cable won’t fit. Apple’s adapter and a Thunderbolt 2 cable connect it. Use a late 2015 iMac as a monitor
• No cable: Wi‑Fi works with every one of them.

Use a port with the ⚡︎ symbol on both Macs, because not every USB‑C port has Thunderbolt. Thunderbolt: which cable and which port? Which model is yours? Which iMacs can be a display

Picture quality

Over a Thunderbolt cable the picture is exactly what your MacBook draws, at full resolution and 60 frames per second. In our test, a MacBook Pro with M3 Pro sent a moving picture to an iMac 24‑inch with M1 with a median delay of about 9 milliseconds. What “about 9 ms” means

Over Wi‑Fi, Ethernet or a USB‑C cable without Thunderbolt the picture is slightly softer, and the app picks the best quality it can. Use Wi‑Fi or Ethernet

Set it up

1. Download Second Display and open it on both Macs.

2. On the iMac, choose Use this Mac as a display. On an iMac this role is already selected.

3. On the MacBook, choose This is the Mac I work on, and allow Screen Recording (and, on macOS 15 or later, Local Network access).

4. Plug in the cable. The two Macs find each other on their own, and a speed test of about five seconds picks the best quality your two Macs can keep up with.

5. Sign in with email, Apple or Google. This starts the 7-day free trial, with no payment details.

Then click Arrange Displays… in the Second Display menu and drag the iMac to where it stands next to your MacBook. Second Display remembers the position. Arrange your displays

Sound, keyboard and mouse

The iMac shows up as a speaker on your MacBook: choose it in Control Center, and the MacBook’s volume keys set how loud. You keep using the MacBook’s keyboard and trackpad, and the pointer moves onto the iMac like onto any display. Keyboard, mouse and sound

A Mac mini instead?

The same iMac works for a desktop Mac too. Use an iMac as a monitor for your Mac mini

Questions