macOS 27 lets third-party HDR monitors keep HDR at scaled resolutions such as 2560 x 1440macOS 27 lets third-party HDR monitors keep HDR at scaled resolutions such as 2560 x 1440

macOS 27 Golden Gate lets a third-party HDR monitor run in HDR at a scaled resolution such as 2560 x 1440, which macOS Tahoe did not allow.

9to5Mac's Jeff Benjamin reported the change on 5 October while testing Dell's 32-inch UltraSharp U3226Q, a 4K OLED monitor. On macOS Tahoe, he wrote, the High Dynamic Range switch in System Settings, Displays was available when the monitor ran at 1920 x 1080, exactly half its native 3840 x 2160 in each direction. Choosing a scaled setting such as 2560 x 1440 removed the switch and dropped the display back to standard dynamic range. On macOS 27 both can be selected at once, without third-party software.

There is a hardware condition. The combination worked on Benjamin's M4 MacBook Pro. On an M1 Max MacBook Pro, also running macOS 27, he could not select both settings, which suggests the fix depends on the chip.

What Apple says

Apple has not mentioned the change. Its support document on HDR video, read by APPDOOK on 5 October, lists the Mac models that support HDR on external HDR10 displays, from 2018 MacBook Pro and Mac mini models onwards, and says the High Dynamic Range setting appears only for third-party displays that support HDR10. It says nothing about scaled resolutions, refresh rates or which chips can combine them, either for Tahoe or for macOS 27.

The restriction itself is not new. In a February 2024 thread, the maintainer of BetterDisplay, a widely used display utility, said the limit depended on refresh rate and framebuffer size, and dated it to macOS Sonoma 14.0. In that account Apple later relaxed it for M2 Macs while M1 Macs stayed limited, which matches what 9to5Mac found on the M1 Max this week.

Why did scaled resolutions turn HDR off?

Our reading is that it comes down to how macOS scales. A 4K monitor set to look like 2560 x 1440 is not driven at 2560 x 1440. macOS draws the desktop at twice that, 5120 x 2880, and shrinks the result to fit the panel, which is why text stays sharp. That is a much larger image to compose every frame than the 3840 x 2160 the panel actually shows, and HDR adds to the work. A limit that depends on framebuffer size, as BetterDisplay's maintainer described, would bite exactly there and nowhere else.

On that reading, macOS 27 has raised the limit on chips that can carry the load and left it in place on those that cannot. That is our inference from two first-hand accounts, not something Apple has said.

Our take

For anyone who bought an HDR monitor for a Mac, this is a bigger fix than it sounds. On a 27-inch or 32-inch 4K screen, 1920 x 1080 makes everything look oversized, so most owners chose a scaled setting and quietly lost HDR. They were paying for a feature macOS disabled whenever the desktop was set up the way they wanted it.

APPDOOK's caution is about how far the finding reaches. It rests on one reviewer, one monitor and two Macs. Nobody has yet published which chips get the combination, whether the refresh rate has to drop to make it fit, or whether 5K and 6K monitors behave the same way. The M1 Max result matters because M1 Macs are still in wide use, and it is a reminder that a macOS feature can depend on the hardware without Apple's documentation saying so.

What to do is simple. After upgrading to macOS 27, open System Settings, Displays, choose the scaled resolution you prefer and see whether the High Dynamic Range switch stays. If it disappears on an older Mac, the monitor is not faulty: the Mac is applying the same limit Tahoe did. We would like Apple to document the condition, because owners of M1 Macs deciding whether to buy an HDR monitor currently have to learn it by trying.