I recently updated my MacBook Pro 14” (M2) to macOS Tahoe. Since the update, my external display is not being detected when connected via HDMI. However, if I connect my iPad as an external display, both the iPad and the external monitor work. Once the iPad is disconnected, the external display also stops working.
[Re-Titled by Moderator]
Original Title: Tahoe external display not detected
MacBook Pro 14″, macOS 26.0
Hi everyone,
Just spent 2 hours on this and found a fix that doesn't involve buying a USB-C adapter, so I figured I'd share since every thread I read ends with "just get a dongle".
My setup: MacBook Pro 14" M2 Pro, macOS Tahoe 26.5, Samsung monitor over HDMI plugged directly into the Mac's built-in HDMI port. Classic symptom, the monitor powers on but stays black, and the Mac doesn't see it at all. Nothing in System Settings, nothing in system_profiler SPDisplaysDataType, nothing in IORegistry. The same HDMI cable works fine on my TV, and the monitor used to work with this Mac before the Tahoe upgrade.
I tried everything you usually find on forums: multiple HDMI cables, rebooting with the monitor already plugged in, updating macOS (26.4.1 then 26.5), disabling VRR on the monitor, Option+Detect Displays in System Settings. Nothing changed.
What ended up working is one command in Terminal, no sudo needed:
mv ~/Library/Preferences/ByHost/com.apple.windowserver.displays.*.plist ~/Desktop/
Then plug the HDMI cable in, restart via the Apple menu, and on boot the monitor is detected right away.
Why it works. macOS keeps a cache of every display it has ever seen in this file. On my Mac there were 11 configurations stacked up across 8 different displays (old TVs, meeting room projectors, previous office monitors, you name it), and several of them were in a clearly broken state: dimensions of 1x1 pixels, origin coordinates at -3200, a mix of Sequoia and Tahoe formats in the same file. Tahoe became way stricter about validating this file, where Sequoia would just silently ignore invalid entries. So the entire display detection pipeline gets stuck on the first malformed entry it hits, and the HDMI handshake never even starts with a new monitor.
The mv sends the file to the Desktop instead of deleting it, so you have an automatic backup. If anything goes weird you can put it back:
mv ~/Desktop/com.apple.windowserver.displays.*.plist ~/Library/Preferences/ByHost/
Hope this helps someone.
I 100% agree with this sentiment. I'm using the cable that came with my Apple studio display. ***
So now I need to Amazon a new cable??? Really????
We need an official statement from Apple and a po to charge the new cables to.
[Edited by Moderator]
jimmmyjimmyjimmy wrote:
Apple screwed the dog by not alerting users that their upgrade was going to break the external display functionality.
Yet somehow, my two Macs running 26.3.1 (16” M4 Pro MBP and 16” M1 Pro MBP) continue working just fine with my LG 5K:2K display (via a Stone Pro dock) that I’ve used for years. Same high-quality, short TB3 cables the whole time.
This works! I went through several other recommendations (ex: New cables, resetting monitor settings, & rebotting Mac) and non worked. This is the correction needed to restore connectivity to an external monitor after the MacOS Tahoe upgrade. Thanks!
May/2026, had this issue after updating to Tahoe 26.5, and veronyka98's suggestion fixed on the first try.
This:
sudo rm -f /Library/Preferences/com.apple.windowserver*.plist
Didn't work, but the rest was fine and fixed.
Thank you!
Thank you. This was driving me crazy after the recent Tahoe update and this fixed me right up!
I have Time machine set for all of my Macs. Just never needed to use them before :D
Thank you so much! I was about to roll back to the previous version of the OS, that would’ve been a hassle.
Thank you for this!! Fixed for me too, finally, after these steps.
Apple just (November 3, 2025) released macOS Tahoe 26.1. We'll see soon enough if the update fixes the problem.
This worked for me. I only had to the first and third commands though.
Did the job for me (for now), thank you very much!
Many, many thanks for posting this - it worked perfectly!! So relieved it is working and so grateful you posted the fix. Have a great holiday!
Thankyou, this worked for me.
I have the same issue. I've used USB-C cables directly from Apple and LG, and this still does not resolve this problem.
Do you have an M chip macbook or 2020 or older
External display not detected after macOS Tahoe update via HDMI
