YouTube is currently testing an enhanced version of 1080p resolution.
Improved 1080p resolution; Image: 9to5Google
YouTube has been testing an enhanced 1080p resolution to a few YouTube Premium subscribers since yesterday. The bitrate increases from 8 Mbps to 13 Mbps in this feature. YouTube is enabling this option for premium users because otherwise it would be expensive to run the video at full bitrate and needs a lot of bandwidth.
The 1080p resolution will still be available for all users, YouTube said. The 1080p premium resolution is a small perk for premium users. Last year, YouTube ran tests that made 4K videos available only to premium users. Currently, 4K is available to everyone again, but it's not known what will happen next.