"The streamers [Hulu, Amazon, Netflix] don't share their ratings, but a new measurement looked at streams, viewers, engagement and more to determine which series have the biggest audiences," per Hollywood Reporter:

"Of the premium content offered by the Big Three streamers, the most popular shows in September from each were The Handmaid's Tale (Hulu), The Man in the High Castle (Amazon) and Narcos (Netflix), according to Parrot Analytics."