Mac Studio won't detect working hdmi monitor

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Level 1

49 points

Mac Studio won't detect working hdmi monitor

I have a Mac Studio where I have successfully been using 3 monitors. However, at some point recently, I changed the resolution of one of my monitors, and from that point on, after rebooting, I cannot connect that HDMI monitor successfully to my computer. It's a very strange set of circumstances.

Some facts:

During cold boot, the monitor that seemingly doesn't work, shows the Apple logo, but will never be detected by the computer for use.
In safe mode, if I UNPLUG the offending monitor, Mac pretends to detect it, but as soon as I plug it back in, it acts like it's no longer there.
Yes, I have plugged the monitor directly into the HDMI port on the Mac Studio with multiple working cables with no luck.
Yes, another monitor works fine plugged into that same HDMI port.
Yes, I have erased the com.windoserver.* files in all preferences directories, no luck
Yes, the monitor works fine on another computer, with the same cables

As you can see, I've tried many different troubleshooting steps. I theorize that the Mac Studio has some sort of setting that is preventing it from recognizing or at least accepting a handshake with the monitor.

Mac Studio, macOS 26.0

Posted on Oct 12, 2025 2:37 PM

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Answer 1

Mike Safar Author

Level 1

49 points

Oct 12, 2025 3:39 PM in response to Mike Safar

Well, I fixed it with a more thorough deletion of preferences files. There were a few com.apple.windowserver files in other directories I didn't know about. Google Gemini created a script that did the trick.

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Answer 2

Oct 12, 2025 4:18 PM in response to Mike Safar

For MacOS 12 Monetary and some later versions, some users got relief by deleting some preferences files, then Restarting:

Library/Preferences/com.apple.windowserver

-AND-

~/Library/Preferences/com.apple.windowserver.<UUID>.plist -OR-

~/Library/Preferences/ByHost/com.apple.windowserver.<UUID>.plist

-- where [~] tilde is an active abbreviation for "current user"

-- and <UUID> is a string of hexadecimal numbers unique to your system, grouped as 8-4-4-4-8 hexadecimal digits

Restart REQUIRED after these deletions.

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Answer 3

Oct 12, 2025 2:47 PM in response to Mike Safar

<< [tried] multiple working cables >>

That is a hedge against BROKEN cables.

HDMI cabling is like black magic. Finding a solution that actually works can be very difficult.

The Mac is very fussy about its connection to displays, and insists the there be NO transmit errors whatsoever.

HDMI cables you want for HDMI-only Displays (higher resolutions than 720p TV sets) are marked as Certified with an anti-counterfeiting tag and are labeled:

"PREMIUM High Speed HDMI cable" or that + "with Ethernet" (up to 4K at 30Hz) --OR--

“ULTRA High Speed HDMI cable" or that + "48G" (supports higher resolutions and backward-compatible)

Cables with No Certification tags are good for your standard 720p TV set, and not much more.

HDMI was invented for HD TV sets. it works great at its original resolution of 720i or 720p. At higher resolutions, it quickly develops issues that are complex to solve, and the cables and adapters required to solve are NOT intuitive.

--------

there are two important additional issues:

¿what model year Mac Studio?

¿what make&model display?

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