Setup
From download to second screen.
About five minutes, most of it spent walking to the other Mac. Do every step on both machines unless it says otherwise.
Before you start
- Two Macs, both running macOS 13 Ventura or later.
- A Thunderbolt 3 or Thunderbolt 4 cable, or a USB-C cable rated for USB4 at 40 Gb/s. A charging cable will not do — many USB-C cables carry power and almost no data, and they look identical.
- Both Macs awake. A sleeping Mac drops off the link like any other computer.
For the full 5120 × 2880 at 60 Hz, the receiving Mac needs to be a Retina 5K iMac (2017), iMac Pro, iMac (2019) or iMac (2020). For 120 Hz, it needs to be a ProMotion MacBook Pro — the 14-inch or 16-inch models from 2021 onward. Any supported Mac works as a display; those are just the ones whose panels can do those numbers.
1. Install it on both Macs
Download DisplayBridge and drag it to Applications. Then do the same on the other Mac — copy the app across, or download it there too.
It is one app, 6 MB. There is no separate sender download and no separate receiver download, and the Mac that only acts as a screen never needs a license.
2. Open it on both Macs
The first time you open it, macOS asks for Local Network permission. Allow it on both Macs — this is what lets the two find each other over the cable. If you dismiss it, the receiver list stays empty and nothing else will make sense.
If you already clicked "Don't Allow": System Settings › Privacy & Security › Local Network, and switch DisplayBridge on.
3. Allow Screen Recording — on the sending Mac only
The Mac whose screen you want to see on the other one needs Screen Recording permission. macOS classes reading the pixels of a desktop as privileged, whatever you do with them afterwards.
The app shows a card with a button that takes you straight there. By hand: System Settings › Privacy & Security › Screen & System Audio Recording, switch DisplayBridge on, then reopen the app — macOS only hands the permission to a freshly started app.
The Mac that only shows the picture does not need this and will never ask for it.
4. Connect the cable
Plug the Thunderbolt cable into both Macs. Nothing to configure: macOS builds the Thunderbolt Bridge between them on its own.
Give it up to about twenty seconds. After a cable is plugged in, macOS spends a moment sorting out addresses on the new link before the two Macs can see each other. This is normal and it happens on both ends.
5. Click Connect
On the sending Mac, the other machine appears in the list by name. Click Connect. The other screen goes dark for a moment and then shows your second desktop.
From here the session card shows the frame rate and latency, and lets you drive the other Mac's brightness and volume. To end the session, click Stop — or press Esc on the receiving Mac.
6. Arrange the display
On the sending Mac, open System Settings › Displays. The new screen is there like any monitor. Drag it to where the other Mac physically stands, so your pointer crosses at the right edge, and set the resolution if you want something other than native.
macOS remembers the arrangement, so you only do this once.
When something does not work
The other Mac is not in the list
- Wait twenty seconds after plugging the cable in. This is by far the most common cause.
- Check Local Network permission on both Macs (System Settings › Privacy & Security › Local Network). One machine with it switched off is enough to make the list stay empty.
- Check the cable. Try a different one, ideally the one that came with a Mac or a display. A power-only USB-C cable shows no symptom other than this.
- Make sure the other Mac is awake and has DisplayBridge open.
- Still nothing? Use Connect to address… under the list and type the other Mac's address from System Settings › Network › Thunderbolt Bridge. This bypasses the discovery step entirely.
It says the host is down
Almost always a receiving Mac that went to sleep, or a cable that was unplugged. Wake it, or replug and wait the twenty seconds.
Connect does nothing, or the screen stays black
Screen Recording permission on the sending Mac, nine times out of ten — and specifically, the app not having been reopened after the permission was granted. Quit DisplayBridge completely and open it again.
The frame rate looks low
An idle desktop produces almost no new frames to send, so a low number on a still screen is correct behaviour, not a fault. Move a window or play a video and watch it climb.
The receiving Mac keeps falling asleep
It will not while a session is running — the app holds its display awake for as long as it is showing something. Before you connect, though, it sleeps like any Mac.
Updating
The app checks for updates by itself and installs them in place; there is nothing to re-download. Every 1.x update is included in the price. Update both Macs when one prompts you — running different versions on the two ends is the single most confusing thing you can do to yourself.
Uninstalling
Drag it to the Trash. There is no installer, no kernel extension, no login item and no background service, so there is nothing left behind. If you want to be thorough, remove it from the Screen Recording and Local Network lists in System Settings › Privacy & Security afterwards.
Still stuck?
Write to [email protected]. Tell us which two Macs, which macOS versions, and where in the list above it stopped working — that is usually enough to answer in one reply.