The YouTube app now supports HDR video streaming on the iPhone 8, iPhone 8 Plus, and iPhone X. The feature kicks in automatically, so no app update is necessary. From that point you will have the ability to pick from different HDR resolutions. YouTube's HDR support so far has been available to handful of devices such as LG V30, Google Pixel 2 and Sony's latest Xperia XZ.
HDR video support on YouTube has always been limited to select smartphones, mostly flagships.
While YouTube began rolling HDR content in back in 2016, Apple, on the other hand, debuted support for HDR content with its "Super Retina" display in iPhone X past year. While we are talking about FaceID, it is worth mentioning that all three rumoured iPhone devices that are expected to arrive later this year, are said to feature FaceID and the "notch" on the display.
The iTunes Movies Store on Apple TV 4K also supports 4K, HDR10, and Dolby Vision for a handful of movies when plugged with a 4K compatible TV. However, it should be paired with 4K-enabled TV sets. HDR stands for High Dynamic Range and it provides a wide range of enhanced color options in videos. However, the maximum resolution offered by these videos is 1920x1080 pixels and the service is yet to roll out true 4K quality video which have a resolution of 3840x2160 pixels.