Most likely you're watching in 720p. In Chrome, Firefox and Opera you're getting 720p max. To get 1080p you need to be watching in Internet Explorer, Safari or on a Chromebook. To get 4k you need to be watching in Edge and have a 7xxx or 8xxx Intel CPU and HDCP 2.2 enabled display. Source: https://help.netflix.com/en/node/23742