Starbucks is expected to be the most popular proximity-based mobile payments service operator in the US in 2018, topping anticipated frontrunners like Apple Pay, Google Pay and to a lesser degree, Samsung Pay.

A recent report from eMarketer forecasts 23.4 million people in the US will use the Starbucks app to make a point-of-sale purchase at the coffee chain at least once every six months. The firm estimates that 22.0 million people will use Apple Pay, 11.1 million will utilize Google Pay and 9.9 million will take advantage of Samsung Pay for at least one proximity mobile payment transaction.

eMarketer highlights Apple Pay's second-highest adoption rate despite the fact that it launched first and is accepted at more than half of US merchants. Google Pay isn't as widely accepted, the firm notes, but it does benefit from being pre-installed on Android phones. Samsung Pay may have the lowest adoption but eMarketer claims it is the most widely accepted by merchants.

Starbucks launched its mobile payments program in early 2011, allowing customers to use their smartphones to pay for purchases made at thousands of retail stores across the country.

eMarketer notes that while each of the top four apps will continue to gain users in the US, their share of mobile payment users will continue to drop as new payment apps enter the market. This is especially true of merchant-branded mobile apps like Starbucks.

For the first time ever, more than a quarter of US smartphone users 14 and older will make a proximity mobile payment in 2018.