Web for 3840x2160 - What's in the future, what course?

Hello. What will in HTML5 for 3840x2160 in PC and laptops?

You should probably be more specific.

That’s up to the operating system, I think. I would expect that a 4K screen is used in such a way that the effective resolution is 1080p. The scaling is then exposed as a device pixel ratio of 2.