The Walking Dead has sold 8.5 million episodes across its five episodes, according to TellTale CEO Dan Connors.
Speaking to the Wall Street Journal, Connors said the figure was based on the first seven months of the series' availability.
"November and December were our biggest months," he said. "It was the culmination of the product, the game of the year awards, the retail push and it still has a ton of head room in it."
He continued: "The episodic model has allowed us to create an economy that works on mobile. As far as size, at this point it's probably about 25% of the revenue of the product and it is on the largest upswing of all platforms as well."
On why TellTale decided to offer the first episode free for a limited time, Connor said it was a way of attracting new users. "That opens the funnel and gets it out to more people who can then convert into the game."
In other news, Connors told Red Bull UK last week the studio is looking at ways user choices made in the first season can be implemented in a forthcoming second season. "We are definitely figuring out how to carry the saves over," he said.