PayPal Inc. today said it has acquired Honey Science Corp., a web browser extension and coupon site, for $4 billion in a mostly cash deal.

Founded in 2012, Honey pitches itself as a site that helps people make smarter choices when they shop online. The company primarily offers a browser extension that helps shoppers by finding them deals and applying coupon codes. Honey makes its money through affiliate links and has more than 10 million users.

It’s the largest acquisition in PayPal’s history, at least after its independence from eBay Inc. It’s also somewhat strange. PayPal is best known as an online payment provider and, though it powers countless millions of e-commerce sites, it has never been a player in the coupon and affiliate business before.

PayPal is pitching the acquisition as both a technology and pro-consumer buy.

“Honey is amongst the most transformative acquisitions in PayPal’s history,” Dan Schulman, president and chief executive officer of PayPal, said in a statement. “It provides a broad portfolio of services to simplify the consumer shopping experience, while at the same time making it more affordable and rewarding. The combination of Honey’s complementary consumer products with our platform will significantly enhance our ability to drive engagement and play a more meaningful role in the daily lives of our consumers.”

Schulman added that it’s another way to help businesses that use PayPal “build and strengthen their customer relationships, provide personalized offers, and drive incremental sales.” Honey will be pitched to PayPal’s network of merchants as a way to allow them to offer targeted and personalized promotions.

The most obvious concern will be whether PayPal favors Honey’s 30,000 clients over other users. Honey will continue to operate as a semi-independent company, maintaining its Los Angeles headquarters with its co-founders staying on post PayPal acquisition. That said, competitors to Honey, many of which use PayPal payment services, will be deeply concerned.

Honey had raised $31.8 million in venture capital funding. Investors include Athos Capital, Ludlow Ventures, Mucker Capital, Cendana Capital, Wonder Ventures, Bam Ventures, Plug and Play and SXE Ventures.

Image: Honey