How to use an iMac as a monitor for a Mac mini

In this guide, Mac mini means the Mac running DispMiniSender, and iMac means the Mac running DispMiniReceiver. If you use a MacBook or Mac Studio as the Sender, the same steps apply.

What you need

• Sender: Mac mini or MacBook with Apple silicon, macOS 14 or later
• Receiver: iMac from 2017 or later, macOS 13 or later
• Cable: Thunderbolt 3 or later, or USB4 data cable

A USB-C charging cable can look identical but won't work, because it doesn't support Thunderbolt or USB4 data links. Look for a Thunderbolt symbol or a 40Gbps USB4 marking on the cable.

If your Mac mini has no screen attached, connect one temporarily or use remote desktop for the first setup. macOS permission prompts must be clicked by hand.

1. Connect the Macs

Plug the cable directly into a Thunderbolt or USB4 port on both Macs. On a Mac mini with M4 or M4 Pro, use the ports on the back, because the front USB-C ports aren't Thunderbolt. You don't need to change any network settings.

2. Install the apps

Download both apps from Releases, then move each one to the Applications folder:

• DispMiniSender goes on the Mac mini or MacBook.
• DispMiniReceiver goes on the iMac.

If macOS says it can't verify the developer, go to System Settings → Privacy & Security and click Open Anyway.

3. Set up the iMac

Open DispMiniReceiver. On macOS 15 or later, allow Local Network access when asked. It then waits for a connection.

4. Set up the Mac mini

Open DispMiniSender. It runs in the menu bar, so no window or Dock icon appears. Allow these permissions:

• Local Network lets it find the iMac. macOS only asks for this on macOS 15 or later.
• Screen Recording lets it send the picture. Newer versions of macOS call this Screen & System Audio Recording.

If nothing happens after you allow Screen Recording, quit DispMiniSender and open it again.

The Sender finds the iMac and connects, and the iMac switches to fullscreen showing your Mac mini's desktop.

5. Start both apps automatically

Neither app starts automatically until you set this up:

• On the Mac mini: turn on Launch at login in DispMiniSender's settings.
• On the iMac: DispMiniReceiver has no setting for this. Go to System Settings → General → Login Items (Login Items & Extensions on macOS 15 or later), click + under Open at Login, and choose DispMiniReceiver.

Apps only start after you log in. If your Mac mini has no screen, turn on automatic login in System Settings → Users & Groups, which lets anyone with physical access use that Mac. Automatic login isn't available while FileVault is on, and a Mac with FileVault on must be unlocked with a directly connected keyboard after each restart (remote desktop and DispMini cannot run before FileVault unlock).

Everyday use

Once both apps start automatically, turn on both Macs and they reconnect by themselves.

Use the iMac's keyboard and mouse

Keyboard and mouse sharing is off by default.

1. On the iMac, turn on Allow controlling the sender with this Mac's mouse and keyboard in DispMiniReceiver's settings.
2. On the Mac mini, allow Accessibility access when asked.

Input is only sent while the DispMini picture is fullscreen and on screen. Swipe to another desktop and your keyboard and mouse control the iMac again.

Check your connection

Click the DispMini icon in the Mac mini's menu bar. The dot next to each device shows its status:

Optional: turn the dot green

With the cable plugged in, on both Macs:

1. Go to System Settings → Network → Thunderbolt Bridge → Details → Hardware.
2. Set Configure to Manually and MTU to Jumbo (9000).
3. Reconnect DispMini.

To undo this, set Configure back to Automatically.

Optional: shorten the wait with fixed IP addresses

By default, each Mac assigns itself an IP address when you plug in the cable, so you wait longer before DispMini connects. Setting a fixed IP address on both Macs shortens the wait:

1. On each Mac, go to System Settings → Network → Thunderbolt Bridge → Details → TCP/IP.
2. Set Configure IPv4 to Manually.
3. Set IP Address to 10.0.10.1 on the Mac mini and 10.0.10.2 on the iMac.
4. Set Subnet Mask to 255.255.255.0 on both, and leave Router empty.

Change both Macs. If only one has a fixed address, they can't connect over the cable. If your network already uses 10.0.10.x, pick a different range for both Macs.

To undo this, set Configure IPv4 back to Using DHCP on both Macs.

Using Wi-Fi instead

By default, DispMini connects automatically when a cable is plugged in, and not otherwise. Without a cable, click the iMac in the Sender's menu bar panel to connect by hand. Put both Macs on the same 5 GHz network.

To maximize streaming performance and eliminate latency, DispMini does not add application-level encryption on top of the stream. While your Wi-Fi router provides link-layer encryption (WPA2/WPA3), others on the same network may be able to see or interfere with the stream—including keyboard input if keyboard and mouse sharing is on. Only use Wi-Fi on a trusted private home or office network, never on public or shared guest Wi-Fi.

If you only use Wi-Fi, set Auto-connect to Thunderbolt or Wi-Fi in the Sender's settings, then check the receivers that should connect over Wi-Fi.

Update DispMini

• Sender: from version 0.9.0 RC3, you can install updates in one click. When a new version is available, open the About tab in the Sender's settings and click Install and Relaunch. DispMiniSender must be directly in the Applications folder. The picture is interrupted for a few seconds while the app relaunches.
• Receiver: install updates by hand. Quit DispMiniReceiver, then download the new version from Releases and move it to the Applications folder.
• Updating the Sender from RC1 to RC3: this is also a manual install, because RC1 doesn't have the button. Follow the same steps as for the Receiver.

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