https://www.theverge.com/2018/9/26/17906234/youtube-hdr-apple-iphone-xs-max-ios-app

Apple might not be using the codecs that YouTube prefers, but that doesn’t mean you’ll be getting a second-rate viewing experience on the latest iPhones. YouTube has updated its iOS app and added HDR support for the iPhone XS and XS Max, as noticed by AppleInsider.

The phones were released on Friday, and in the few days since launch, users have noticed that they couldn’t play high dynamic range content from the service — whereas the iPhone X, 8 Plus, 8, and iPad Pro all can. YouTube didn’t have HDR ready in time for Friday, but thankfully the company didn’t take long to roll out compatibility for the wider color gamut and more vibrant, splashy video. It took YouTube until May to introduce HDR support for the 2017 iPhones after it debuted on Android last September. The highest resolution you’ll be able to get from YouTube on either new iPhone XS model is 1080p.