This fellow has a much more reasonable argument as to why this happens https://www.reddit.com/r/ios/comments/z2n4h5/why_does_youtube_on_safari_max_out_to_720p_

This fellow has a much more reasonable argument as to why this happens https://www.reddit.com/r/ios/comments/z2n4h5/why_does_youtube_on_safari_max_out_to_720p_i_have/ixhj65a/ https://www.reddit.com/r/ios/comments/z2n4h5/why_does_youtub... About iPhones not supporting Media Source Extensions, while the iPad does.