[GRiMe2D]

MacBook Pro can “display” HDR content on SDR displays.

macOS puts a slightly higher brightness than it required and artificially (in software) changes absolute white (0xFFFFFF) to greyish color (0xEEEEEE). So when a HDR content is required it will remove mask around that content. Safari ideally, probably that’s on Firefox why tone mapping doesn’t work well

[badc0ffee]

There's a HDR video on that page, and on my built-in MBP display, it's much brighter/has noticeably more range than the rest of the UI. Moving the window to my non-HDR external 4k monitor, it looks like a regular YouTube video.

The video looks the same in both Safari and Firefox, whereas the images are dim in Firefox on both my MBP display and external monitor.