4K Ultra HD, 4K Blu-ray and High Dynamic Range support
This is arguably the most important feature of the Xbox One S. Not only does the Xbox One S support 4K video playback from streaming services like Netflix and Amazon, it also has a 4K Ultra HD Blu-ray built-in.
Plus, it can upscale games to 4K
When the Xbox One S was first announced, Microsoft neglected to mention that the new console is also capable of upscaling games to 4K.
The upscaling capabilities were revealed by Jeff Henshaw, Group Program Manager at Xbox at an E3 session (via TechRadar).
Henshaw said: "It's not native 4K, but the Xbox One S can upscale games from 1080p to 4K."
Read more at
http://trustedreviews.com/opinions/xbox-one-s-vs-xbox-one#E9xGAm6qvP4gXXSc.99
Project Scorpio, tentative release December 2017, will have native full 4k 60Hz game capability.
Xbox One has hdmi 1.4a so technically capable of 4k playback at 30Hz, which is useless for games but adequate for media content. Xbox One S has hdmi 2.0 so is capable of 60Hz