Multiple iPhone users running the first developer beta of iOS 14 are reporting that they are now seeing their YouTube video resolution going all the way up to 2160p or 4K. YouTube resolution has been limited to all iOS and iPadOS devices due to a codec compatibility issue. YouTube encodes its videos in two codecs, AVC1 (h.264) or Google's own VP9. However, while VP9 encoded videos are available in all resolutions and frame rate options, AVC1 encoded videos are only available up to 1080p60 resolution. First: MKBHD video, maxed out at 1080p, AVC1Second: 4K60 HDR video, maxed out at...
Source: https://www.gsmarena.com/ios_14_beta_users_report_seeing_4k_option_in_the_youtube_app-news-43941.php
