M5 Pro MacBook Pro: Third display not detected

I ran into the same third-display limitation on an M5 Max and found a workaround that gives me three Studio Display XDRs (2026) at once, so I'm posting it here in case it helps anyone in this thread.

My setup: MacBook Pro 16" M5 Max (128GB), macOS Tahoe 26.6.2, 3x Studio Display XDR. Same symptom as described above — only two XDRs would come up, the third got no signal, and lowering the refresh rate to 60Hz in System Settings made no difference. This matches what you observed: macOS seems to allocate display resources at link training time based on the display's EDID-declared maximum (5K@120Hz), not the mode you actually select.

What worked:

1. Plug a 4K UHD 60Hz HDMI dummy plug into the HDMI port FIRST, before any display is connected. (Critical.)
2. Connect the three XDRs, leaving a short pause between each. Both topologies worked for me: all three directly to the Thunderbolt ports, or all three daisy-chained with a single cable to the MacBook.
3. At this point only one or two of the three will be on. NOW remove the dummy plug. (Just as critical as step 1 — all three will not come up while the dummy is still attached.)
4. The moment the dummy is removed, the remaining display(s) come up.

Result: one XDR at 120Hz, the other two at 60Hz. This survives reboot and sleep/wake, and works both in clamshell mode and with the lid open. My daily setup is now all three daisy-chained with one cable.

My understanding of why it works: with the dummy taking up part of the display budget, the XDRs negotiate at 60Hz during link training instead of demanding a 120Hz-class pipe. Removing the dummy then frees that budget so the remaining display can come up, while the already-negotiated links stay as they are.

For anyone else trying this, these did NOT work for me: setting 60Hz in System Settings and reconnecting, Thunderbolt 5 docks (they don't raise the maximum display count), and changing connection order without the dummy plug.

Title: Fixed: Mac mini M5 Pro detects only two of three displays — dual ASUS XG27JCG + BenQ 4K

I finally got all three monitors working together after hours of troubleshooting. Sharing what worked in case it helps someone with a similar setup.

My setup

• Mac mini M5 Pro, macOS 27.0
• Two ASUS XG27JCG monitors, connected directly by USB-C
• BenQ EW2880U, connected by HDMI

Any two monitors worked. Connecting all three left one showing “No signal.” Disconnecting a working monitor would let the other one activate.

Changing ports, restarting, and setting both ASUS monitors to 60Hz in macOS did not solve it.

What the diagnostics showed

Both ASUS monitors still advertised their high-refresh 5K capabilities, even when I selected 60Hz. The Mac’s low-level connection report showed two display pipes allocated to each ASUS, with no assignment for the BenQ.

An Apple Developer Forums discussion describes a related issue: display resources can be allocated according to the monitor’s advertised capabilities at connection time. Simply lowering the refresh rate afterward may not release those resources. That discussion involves different ASUS monitors, so it isn’t proof that every similar symptom has the same cause.

What worked

We exported each ASUS monitor’s EDID—the data describing its identity and supported display modes—and created a separate modified profile for each one.

The profiles:

• Preserved each monitor’s identity.
• Retained its existing supported 5120 × 2880 at approximately 60Hz timing.
• Removed higher-refresh modes and, for this workaround, HDR/VRR/audio capability advertisements.

After applying those profiles, the Mac allocated one display pipe per ASUS. I then disconnected and reconnected only the BenQ’s video cable, leaving both ASUS monitors connected.

All three started working:

MonitorWorking resolutionASUS XG27JCG #15120 × 2880 at 60HzASUS XG27JCG #25120 × 2880 at 60HzBenQ EW2880U3840 × 2160 at 60Hz

Keeping the fix active

We initially saved and automatically reapplied the profiles using BetterDisplay’s custom EDID feature. Later, we replaced that with a small custom utility that reapplies the same profiles at login and when needed. BetterDisplay is now closed, and the setup works independently of it.

I restarted afterward and the setup is working. One ASUS did go black during earlier testing; turning that monitor off for 10 seconds and back on restored the picture.

Important limitations

This is a workaround tested on my specific monitors, not an official Apple fix. It limits my ASUS monitors to 60Hz and disables their HDR/VRR capabilities. The custom utility uses an undocumented macOS API, so future updates could affect it.

Do not blindly import someone else’s EDID file. Back up your own monitor’s EDID and preserve its identity and supported timings. Even my two identical ASUS monitors needed individually matched profiles.

The useful finding is that selecting 60Hz in macOS and limiting the capabilities advertised by the monitor are different things. In my case, changing the advertised capabilities was what finally allowed all three displays to work.

nullvoid324 wrote:

• ASUS XG32UCG

Asus – ROG Strix XG32UCG ROG Strix XG32UCG Gaming Monitor – 32-inch (31.5 inch viewable) 3840x2160, dual mode (4K 160Hz/ FHD 320Hz)

This monitor has DisplayPort v1.4, USB-C (DIsplayPort) and HDMI v2.1 inputs.

• ASUS VG27AQ

• ASUS VG27AQ3A

Asus – TUF Gaming VG27AQ HDR Gaming Monitor – 27 inch QHD (2560x1440), IPS, 165Hz

Asus – TUF Gaming VG27AQ3A Gaming Monitor – 27-inch, QHD(2560x1440), 180Hz,

These monitors each have a DisplayPort v1.2 input, and two HDMI v2.0 inputs.

I can get 2 monitors working, but the 3rd is never detected, even when I try connecting it directly to the MacBook Pro using either HDMI or USB-C to DisplayPort.

All three of your displays have maximum refresh rates in excess of 144 Hz. The specifications for the M5 Pro MBP indicate that when you use displays with very high resolutions (e.g., 8K) or refresh rates, you reduce the maximum number of external displays that you can have from three to two.

--------------------

M5 Pro

Supports up to three external displays over any combination of Thunderbolt and HDMI ports:

• Three displays up to a native resolution of 6K at 60Hz or 4K at 144Hz or
• One display up to a native resolution of 8K at 60Hz or 5K at 120Hz or 4K at 240Hz plus a second display up to a native resolution of 5K at 120Hz or 4K at 200Hz

--------------------

If I disconnect the dock and connect only a single display directly to the Mac with an HDMI cable or USB-C to DisplayPort cable, that display works fine.

If I connect the dock and with two displays connected to the dock, both displays work fine.

Either of those configurations would appear to fall within the limits mentioned in Technical Specifications.

Any attempt to have 3 displays connected simultaneously in any configuration results in only 2 displays being detected.

Plug in that third display, now you are outside the limits. Quite possibly, the MBP, having learned the capabilities of the other displays, has set up resources for the high-refresh-rate, two-display-maximum case.

I also had the same issue with the same model of MacBook (m5 pro). I was able to resolve this by editing the UI Settings on the monitors themselves. In order to make the Thunderbolt 5 dock recognize all three displays when plugging it into the MacBook, I had to turn off DSC on each of the monitors I have. Once I did this, all of the displays were recognized every time I plugged them in. Hopefully this helps you as much as it did me.

I’m seeing a consistent display-detection issue with both my M5 Max and M5 pro MacBook Pro when using two Studio Display XDRs plus a third 4K monitor.

My setup:

• MacBook Pro with M5 Max and M5 pro
• Two Apple Studio Display XDRs, connected via Thunderbolt 5
• Third 4K display: tested with both Dell U2725QE and an EIZO 4K monitor
• Third display tested via both HDMI and USB-C/Thunderbolt

The issue appears to depend heavily on connection order.

What works:

If I connect the 4K display first, then connect the two Studio Display XDRs in a Thunderbolt daisy chain, all three displays can work.

What does not work:

If I connect the two Studio Display XDRs first, then connect the third 4K display, the 4K display gets no signal.

This happens whether the third 4K display is connected via HDMI or USB-C/Thunderbolt.

Additional observations:

• If all three displays are connected and the 4K display has no signal, unplugging either one of the Studio Display XDRs immediately restores signal to the 4K display.
• Lowering the Studio Display XDRs to 60 Hz does not fix the issue.
• Using three separate ports instead of daisy chaining shows similar connection-order behavior.
• The same behavior occurs with both the Dell U2725QE and an EIZO 4K display, so it does not seem specific to one monitor model.
• Since the same hardware and cables can work when connected in a different order, this does not seem like a simple GPU capability issue or a single bad cable.

My impression is that this may be a macOS / Apple Silicon / Thunderbolt display-allocation or hot-plug negotiation issue. It seems that when the two Studio Display XDRs are connected first, macOS allocates display resources in a way that prevents the third 4K display from being activated. However, when the 4K display is connected first, macOS appears to choose a different allocation that allows all three displays to work.

Has anyone else seen similar behavior with multiple high-resolution Thunderbolt displays on Apple Silicon, especially with daisy-chained Studio Display XDRs or connection-order-dependent behavior?

All three of your displays have maximum refresh rates higher than 144 Hz. One is a 160 Hz monitor, another is a 165 Hz monitor, and the third is a 180 Hz monitor.

I do not know for certain whether it is a display's maximum refresh rate, or its current rate, that counts against the limits. That said, it seems reasonable that the maximum rate might count. Especially since that is consistent with the behavior that you observed.

This fixed my issue - I had 1 monitor which had the DSC setting, once I turned it off - I no longer have any issues.

This is a true gem of Display-connecting wisdom:

<< MacOS seems to allocate display resources at link training time based on the display's EDID-declared maximum (5K@120Hz), not the mode you actually select. >>

My Corollary:

MacOS is currently NOT factoring in whether the currently-connected cables and adapters are actually capable of supporting the top specs the display might be innately capable of achieving. If any transmission errors occur, the display often drops out with no apparent explanation.

Some users got relief by connecting their HDMI display first.

You should connect that ASUS XG32UCG using DIRECT HDMI port out of the Mac, because that is the highest speed interface the display supports.

Use extreme caution when connecting displays using USB-C to DisplayPort. If the supported port of the computer or Dock really is a USB port, it may be limited to 10 G bits/sec, and some adapters are also limited. Connecting that to a DisplayPort 2.1 input can NOT get you close to 40 G bits/sec operation, because the pinch point is USB-C at 10 G bits/sec.

I would mention in passing that there is a fairly new Thunderbolt5 to DisplayPort 2.1 adapter from CableMatters available. HOWEVER, your ASUS XG32UCG does not support that speed on its DisplayPort 1.4 input, which is limited to HBR3 at 25.92 G bits/sec PROVIDED you are driving it with a Thunderbolt output, not merely USB.

HBR3 is limited to 4K at 10 bits/color at 75 Hz without Display Stream Compression.

What we suspect is happening in cases like this is that the Mac sees it can not attain the highest speeds directly. This is often due to protocols limited to only certain speeds, and not using the maximum possible speeds the interface could theoretically support.

So it uses up TWO display generators and divides the display into Left and Right halves. In some cases, this composite data stream is faster. That reduces the Total number of displays that can be supported by one.

When it crashes, there is a very telling artifact, where you can see that the left and right halves are being treated separately:

I am facing the same issue as you.

MacBook Pro M5 MAX

2 x Apple Studio Display XDR

1 x LG 45GX950 45" 5K Monitor

I can connect 2 monitors but not the third. The third just wont detect.

Did you ever find another solution for this?

<< My daily setup is now all three daisy-chained with one cable. >>

The first XDR display at 120 Hz consumes about 75 percent of a nominal 80 G bits/sec DisplayPort channel, UHBR 77.37 G bits/sec.

When all are on one cable, the second and subsequent may be 'starved' for bandwidth on that one cable and may be forced to rely on Display Stream Compression rather strongly. That Display Stream Compression will eventually not be 'lossless'.

You might find you get better color results connecting fewer displays on the same ThunderBolt-5 cable.

Your M5 MacBook Pro with MAX processor has three ThunderBolt-5 ports.

that ASUS XG27JCG display appears to be a 5120 by 2880 5K display with refresh rates up to 180 Hz

However, it may be severely limited in its ability to support high (uncompressed) data rates when connecting DisplayPort over USB-C due to the display's limitation of USB-3.

interfaces limited to:

• USB-C 3.2 -- limited to USB-3 max of HBR2 at 17.28 G bits/sec (5K at 30 Hz before compression)

• DisplayPort 1.4. -- which could provide HBR3 at 25.92 G bits/sec if derived from a USB-4 or Thunderbolt source with an Advanced adapter (5K at 50 Hz before compression)

• HDMI 2.1 which supports up to 42.0 G bits/sec -- (5K at 60 Hz before compression)

For less compression and somewhat better color, I suggest you consider an advanced (USB-4 -capable) DisplayPort adapter, rather than relying on the display's (hobbled) direct USB-3 capabilities.