Luna Display Mac‑to‑Mac USB Connection Guide

Quick answer: In Luna Display, you can connect two Macs over USB. Just use a direct USB 3.1‑capable cable, run macOS 10.15+ on both machines, plug in, and Luna will auto‑connect.

Table of Contents

USB Mac-to-Mac requirements
Compatible USB cables
How to connect using USB
Troubleshooting USB connection issues

USB Mac-to-Mac requirements

USB Mac-to-Mac mode is only available in Luna Display version 5.3 or later. You’ll need:

macOS 10.15 or later on both your Primary and Secondary Mac
A compatible USB cable (see next section)

Compatible USB cables

You’ll need either a USB-C to USB-C cable or a USB-C to USB-A cable, depending on the ports available on your devices.

Important:

Apple USB-C charging cables (included with iPads and Macs) ARE NOT compatible with Mac-to-Mac mode – they are USB v2 cables while we require USB v3.1 or later.
USB hubs, adapters, or docks are not compatible for Mac-to-Mac USB. Plug the cable directly into the Mac’s port.
USB-A to USB-A cables are not supported.
The USB-A side of the USB-C to USB-A cable must be plugged into the secondary Mac. The primary Mac will not support the USB-A side of the cable.

USB-C to USB-C cables

Use this cable type if both Macs support USB-C. Look for cables labeled USB 3.1 or 3.2 with 20Gbps or higher and 4K @ 60Hz support.

Cables from Amazon we've tested and liked:

IMPORTANT: While we have tested these cables, due to differences in hardware between Mac models, even recommended cables may not work in all setups. Please use discretion when selecting a cable

UseBean USB-C to USB-C v3.2 - 6.6ft

USB-C 3.2 Gen2x2 Cable v3.2 - 6.6ft

USB-C to USB-A cables

Use a cable similar to this type if your Primary Mac supports USB-C but your Secondary only supports USB-A.

Tested cables from Amazon:

Amazon Basics USB-C to USB-A 2.0 - 6ft

Truntau USB-C to USB-A 2.0 Cable - 3.3ft

How to connect using USB

Plug the USB cable directly into both Macs (no hubs or adapters).
Plug the Luna unit into your Primary Mac.
Launch the Luna Display app on your Primary Mac and the Luna Secondary app on the Secondary Mac.
If everything is compatible, Luna will connect automatically over USB.

How to confirm it’s using USB

On your Primary Mac, open the Luna Display app. Look in the upper right corner of the Luna Settings window — if USB is active, you’ll see a cable icon with the word "USB" next to it, as shown in the image below.
USB Connection Troubleshooting

USB isn’t connecting

Check that both Macs are running macOS 10.15 or later
Use a tested USB 3.1 or 3.2 cable — not an Apple charging cable
Make sure your cable is capable of data transfer and is not labeled charging only
Don’t use adapters or hubs — plug the cable directly into the computer’s USB port

Then try this:

Quit both Luna apps on both Macs
Plug in the USB cable
Relaunch the Luna apps
If it doesn’t connect, restart both Macs and repeat the steps above
If it still won’t connect, the cable may not be compatible

Tip: Plug the USB cable in before launching the apps — this improves detection.

"Cannot Use Thunderbolt Accessory" message

This means your cable is not compatible. See our article: Thunderbolt Accessory Error

USB disconnects after sleep

After waking from sleep, Luna may reconnect over Wi-Fi instead of USB. Quit and relaunch the Luna Secondary app to restore USB. This is a known issue we’re working to resolve in an upcoming update.