Whatever Netflix is doing on mobile, it's working. The company's in-app revenue from iOS devices has been growing exponentially over the last few quarters, hitting nearly $120 million in this last quarter alone, according to data from mobile analytics company SensorTower. In late 2015, when it first began to offer in-app subscription purchases, Netflix brought in a mere $11.4 million from iOS devices.

Meanwhile, competitors Hulu and HBO Go have lagged behind. Hulu has seen modest growth every quarter, but it only made $19.4 million in this last quarter from iOS in-app subscriptions. HBO Go, which was raking in the most money in late 2015, has seen its quarterly iOS revenue decline over the past year.

All about the content: It's clear that the original content produced by these companies drives their mobile revenue, which comes from customers purchasing monthly subscriptions. HBO Go, for example, saw a bump in the second quarter of 2016 before a steady decrease, which coincided with the airing of the sixth season of Game of Thrones, its popular TV series. Netflix, meanwhile, has been adding new show after new show to its roster over the last couple of years, including Orange is the New Black, Stranger Things, the Gilmore Girls' revival, Making a Murderer, Master of None, and numerous comedy specials.