I feel bit sorry for Netflix, for the lengths they have gone to get their high performance/reliable architecture but the clients are still at the mercy of the OS, browsers, CPU (decoding codecs) of-course assuming high speed Internet.

From their website - https://help.netflix.com/en/node/23742

Resolution:

Google Chrome Up to 720p on Windows, Mac, and Linux. Up to 1080p on Chrome OS. Internet Explorer up to 1080p. Microsoft Edge up to 4K. Mozilla Firefox up to 720p. Opera up to 720p. Safari up to 1080p on Mac OS X 10.10.3 or later. Streaming in 4K requires an HDCP 2.2 compliant connection to a 4K capable display, Intel's 7th generation Core CPU, and the latest Windows updates.

P.S Interesting to note that Chrome OS plays 1080p, I assume because it has HW acceleration enabled by default (in browser alone, not in android apps though).