macOS Tahoe external monitor issue high GPU usage WindowServer Task

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Level 1

4 points

macOS Tahoe external monitor issue high GPU usage WindowServer Task

Hi everyone,

since updating to macOS Tahoe 26.1, I’ve been seeing very high GPU usage (50–80%) from the WindowServerprocess whenever my MacBook is connected to my Dell U2025QW (5K2K) monitor. This happens even when the system is idle. As a result, the MacBook heats up quickly and the fans ramp up during simple tasks.

If I disconnect the monitor, everything returns to normal. Before the update, the whole setup worked without any issues.

I tested this on two different machines:

MacBook Pro 16” (M1 Pro)
MacBook Pro 16” (M4 Pro)

Both show the exact same problem, so I can rule out a hardware defect.

Setup:

Monitor: Dell U2025QW
Resolution: 5K2K (“Looks like 3840 × 1620”)
OS: macOS Tahoe 26.1

Is anyone else experiencing this?

Are there any known fixes or workarounds?

Thanks in advance for any help!

MacBook Pro (M4 Pro, 2024)

Posted on Nov 18, 2025 1:45 AM

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Answer 1

Nov 18, 2025 10:04 AM in response to Jonaldoou

Jonaldoou wrote:

• MacBook Pro 16” (M1 Pro)

• MacBook Pro 16” (M4 Pro)

• Resolution: 5K2K (“Looks like 3840 × 1620”)

Unrelated question regarding the above, are you able to set the display resolution to 3840 x 1620 on the M4 Pro MBP? This has been a long-standing issue since the M4 came out, affecting ultra wide displays with both MBPs and Minis where the 3840x1620 option disappeared (I can dig out the thread, but the gist was that M1-M3 chips were fine while M4 chips lost the option).

Here's my M1 Pro MBP resolution list for the 5K:2K (after Option-click on the graphical representations):

And here it is from my M4 Pro MBP:

Can you confirm that you do see the 3840x1620 option on your M4 Mac?

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Answer 2

Nemo972

Level 1

8 points

Nov 18, 2025 9:39 AM in response to Jonaldoou

I have no solution, but the same problem with a MacBook Pro 16" (i7 2019). With Tahoe it has become practically impossible to use a video projector: after one or two minutes of HDMI connexion the computer gets so hot that the fans can no longer cope and the system slows down dramatically, projecting PowerPoints is agonisingly slow, projecting video is more or less impossible.

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Answer 3

Nov 18, 2025 9:52 AM in response to Jonaldoou

I also have a 16" M4 Pro MBP running 26.1 and a 5K:2K display (LG, not Dell), and I'm not seeing anything concerning about CPU or GPU usage of the WindowServer process:

Coincidentally, I also have a 16" M1 Pro MBP but that's still on Sequoia so not useful for comparison.

See if the problem is present when you boot in safe mode, which disables 3rd party extensions and performs some system cleanup.

Start up your Mac in safe mode - Apple Support

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