A Mac mini on the desk and an iMac next to it: two screens’ worth of hardware, but only one of them helps the Mac you actually work on. Second Display is one app with two roles. On the Mac mini it is the Mac you work on; on the iMac it is the display. Your windows and your pointer move onto the iMac like onto any other display.
What you need
| Mac | Needs |
|---|---|
| Mac mini | macOS 14 Sonoma or later, and a Thunderbolt port (⚡︎) for the lossless picture. An email address, an Apple Account or a Google account, to start the free trial. |
| 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 Mac mini runs macOS 14? Apple lists the models: Apple: Macs that run macOS Sonoma. For the iMac, see which iMacs can be a display.
Before you start: three things about a Mac mini
- Keep the Mac mini’s keyboard and mouse. In this version the iMac’s own keyboard and mouse don’t control the Mac you work on. The Mac mini’s pointer moves onto the iMac as onto any display, and its keyboard types into the windows there. Keyboard, mouse and sound
- Sound stays on the Mac mini. It isn’t sent to the iMac, so use the speakers or headphones the Mac mini already plays through.
- The iMac is an extra display. Second Display adds a display next to the one your Mac mini already has. Setup on the Mac mini asks you to allow Screen Recording, so you need its own screen for that. We haven’t tested a Mac mini with the iMac as its only display.
Connect them with a Thunderbolt cable
A Thunderbolt cable has room for the whole picture, uncompressed. Each frame of a 24‑inch iMac’s screen is about 17 MB, and 60 of them a second need about 8 Gbit/s: more than Wi‑Fi or an ordinary Ethernet network carries. Use a port with the ⚡︎ symbol on both Macs; not every USB‑C port has Thunderbolt. Thunderbolt: which cable and which port?
Over the cable you can choose Highest quality: lossless, 60 fps, full resolution. In our tests a MacBook Pro with M3 Pro sent Highest to an iMac 24‑inch with M1 at 60 frames per second over a Thunderbolt 4 cable, with a median delay of about 9 ms. We haven’t measured a Mac mini or older and Intel iMacs yet; the speed test recommends the quality your two Macs can keep up. How we measured the delay
No Thunderbolt cable? It still works
- Wi‑Fi or Ethernet. Put both Macs on the same network and Second Display compresses the picture to suit the connection. An Ethernet cable straight between the two Macs works the same way. Use Wi‑Fi or Ethernet
- A USB‑C cable without Thunderbolt. The picture continues over the cable’s USB link, compressed, and moves over to Thunderbolt by itself once the cable comes up as Thunderbolt. A USB‑C cable without Thunderbolt
The picture isn’t encrypted, so use Wi‑Fi and Ethernet on a network you trust, such as your home. How your screen travels
Set it up
Download Second Display and open it on both Macs.
On the iMac, choose Use this Mac as a display. On an iMac this role is already selected.
On the Mac mini, choose This is the Mac I work on, and allow Screen Recording, and on macOS 15 or later Local Network access.
Plug in the cable. The two Macs find each other on their own, and a speed test of about five seconds recommends the quality.
Sign in with your email, with Apple or with Google. This starts the 7-day free trial.
Then click Arrange Displays… in the Second Display menu and drag the iMac to where it stands next to your other display. Second Display remembers the position. Arrange your displays
Pick the size of the picture
In the display’s Resolution menu on the Mac mini, choose Larger Text, Default or More Space. Default matches the iMac’s own resolution, and Retina sharpness and the 60 Hz refresh rate follow the iMac by themselves. Resolution and text size
Which iMac do you have?
Any iMac that runs macOS 12.3 or later can be the display: the models from late 2015 on, up to iMac with Apple silicon. An iMac from 2009 to mid 2014 may still have Apple’s Target Display Mode, but only with a Mac from 2019 or earlier, so not with a Mac mini with Apple silicon. More in use an old iMac as a monitor, a 27‑inch iMac with Retina 5K as a monitor and an alternative to Target Display Mode.