https://www.theverge.com/2017/9/8/16273408/galaxy-s8-note-8-hdr-youtube-app-update-first-phones

The Samsung Galaxy S8, S8 Plus, and Note 8 are the first phones to support HDR videos in the mobile YouTube app. The Verge has been able to confirm that the update is live and offers support for HDR playback at up to 1080p resolution and 60 fps when manually changing video quality. The software update seems to have quietly rolled out yesterday, according to reports on Reddit and SamMobile, which first spotted the update.

YouTube added support for HDR video back in November 2016, but until now the company hasn’t rolled it out to any of the various smartphones that offer HDR screens, like the LG G6 or the Sony Xperia XZ Premium. The update for HDR support seems to only be available on Samsung’s latest smartphones for now, but it’s easy to imagine that Google will continue to build out support for the higher-quality video format on other devices in the near future.