Starbucks has processed more than 42 million mobile transactions in the U.S. since launching its “mobile pay” app for Android and iPhone, according to VentureBeat.

Released in January 2011, mobile pay enables customers to load money onto a digital Starbuck’s card stored on their phone. At checkout, the customer opens the app on their phone and presents a 2D bar code to the cashier, which is then scanned to complete the transaction.

Available also in the U.K. and Canada, mobile pay has proved wildly successful with customers since its launch. In December 2011, Starbucks reported that it had processed 26 million mobile transactions. Not even half a year later that number has jumped to 42 million, indicating a nearly exponential increase in consumer use.

According to VentureBeat, this rapid adoption is prompting Starbucks to continue exploring opportunities in the mobile payments space.

“You’re going to see us as a company that will push the envelope around mobile pay,” chief digital officer Adam Brotman told VB. “We want to innovate in that area before others catch up.”

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