HBO’s standalone streaming service HBO Now, a $14.99 per month over-the-top option for accessing HBO’s premium content without the need for a cable or satellite TV subscription, is atop the iTunes App Store revenue rankings. According to analytics firm App Annie, the HBO iOS app was the highest grossing app on the market in May. While June’s figures have not yet been released, App Annie indicates HBO Now is still performing well. Since Apple has an exclusive launch agreement for HBO Now, this could be the best insight into the service’s traction thus far.

The HBO Now app requires a minimum three-month subscription, but the company has been offering one month free — a strategy that seems to be proving successful.

“Initially, HBO Now was an Apple exclusive — the company first introduced its app and accompanying Web service to those who have an Apple TV, or other iOS devices, including iPhone and iPad,” reports TechCrunch. “Cablevision then became the first pay TV provider to sell HBO Now access to its broadband customers, and streaming cable TV service Sling TV made HBO programming (though not the actual HBO Now standalone app) available to its customers.”

HBO Now will also eventually show up in the Google Play Store with support for Chromecast, but it will have to wait until Apple’s three-month exclusivity window concludes.

“HBO beat out other marginally less expensive streaming service apps like Hulu and Spotify (which cost $13 and $8, respectively) for the number one spot, and it may be that its popularity stems from its stand-alone availability for Apple devices,” notes Digital Trends. “To access HBO from other outlets like Optimum and Sling TV, viewers must bundle the service with another package, like Internet or additional channels.”

“HBO Now’s traction isn’t only indicative of consumers’ interest in ‘Game of Thrones’ and the other popular programming it offers, but instead is a bullet point in a larger trend around cord cutting,” suggests TechCrunch.