Mobile video viewing is huge, and keeps on growing: U.S. Americans spent some 12 billion hours in the top 10 video streaming apps on Android during the 12 months ending July 2017, according to new data from app analytics specialist App Annie. This number grew 45% year-over year.

The list of the most popular Android video streaming apps is led by YouTube, by a wide margin: 80% of those 12 billion hours were spent in the YouTube app alone, according to App Annie. YouTube’s install base on Android is also twice the size of that of Netflix, likely due to the fact that the app comes pre-installed on most Android phones.

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However, premium video services like Netflix are clearly starting to make a dent as well. Not only does Netflix rank second in terms of time spent, but consumers are also increasingly using mobile app stores to pay for their mobile video subscriptions. During the 12 months ending in July, U.S. iPhone and Android users spent a combined $570 million on video streaming apps, according to App Annie.

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As expected, the list of top-grossing apps is led by Netflix, followed by HBO Now. However, the good showing of YouTube is a bit of a surprise: YouTube got ranked third by peak revenue solely based on its YouTube Red subscription tier. The Google-owned video service recently started its own TV subscription offering as well, but YouTube TV is a separate app and thus not included in the revenue for YouTube’s main app.