The reason most websites won't be optimized for 4K resolution is that very few people will be running 4K at 100%; that'd be incredibly tiny on a ~27" monitor. A

The reason most websites won't be optimized for 4K resolution is that very few people will be running 4K at 100%; that'd be incredibly tiny on a ~27" monitor. And even if people were running at that resolution, they'd only actually be using 4K if the app was fullscreened, which seems overkill on a resolution that high. As an example, I myself am running 4K monitors scaled as 2560x1440, so there's no need for apps to optimize for 4K resolution, for me. Just high DPI. If you're talking about optimising a web app you're developing, then you could use a bigger media query that targets 4K resolutions specifically, and handles it specifically. But I'd be surprised if you ever get anyone actually benefitting from that.