“Today we are adding support for High Dynamic Range (HDR) videos on YouTube.” – YouTube.com,  November 7, 2016

Youtube.com has added HDR support for new videos.   Any YouTube creator can now upload videos that use HDR format.  Some currently supported devices include the new ChromeCast Ultra and YouTube capable streaming devices such and some smart TV’s.  Additional device support is expected in the near future for game consoles and other devices.  All HDR videos are backward compatible with legacy devices.  The number of devices that support HDR video playback is expected to grow rapidly.    Here are Instructions for uploading HDR video to   YouTube.com/HDR.  Current support for HDR encoded videos include 10 bit H.264  MOV, MP4, and MKV.

There are several content producers that have begun uploading videos that use the high quality HDR option.

HDR Supported Video Example

More YouTube.com HDR video samples

More details @ youtube.googleblog.com