YouTube rolled out HDR support back in 2016, but it was only limited to pre-recorded content. Now the company has expanded HDR support to livestreams as well, enabling "vibrant experiences in real-time". HDR, or High Dynamic Range, offers a wider range for your content and lets screens that support it display darker shadows and brighter highlights. If you are a creator and want to stream live in HDR, you'll need to use the encoders listed here. SDR (left) vs. HDR (right) Viewers, on the other hand, will need compatible devices to watch live streams in HDR, like the YouTube app...
Source: https://www.gsmarena.com/youtube_hdr_live_stream-news-46656.php
