South Korean ad technology Buzzvil closed its acquisition of Slidejoy, maker of an app that lets users earn money by viewing ads on a phone’s lock screen.

“The combined company will be the global market leader in lockscreen advertising with a geographic footprint in over twenty countries and over 4 billion impressions per month,” Buzzvil said.

Slidejoy pays users in cash or gift cards to view trending news and ads on their lock screen. Cash rewards can be redeemed to PayPal account or donated to charity.

“Slidejoy pioneered lockscreen advertising in the US and became the market leader with over a million users and dozens of advertisers,” Buzzvil said. The firm raised $1.2 million in 2015.

Robert Seo, CEO of Slidejoy, explained that the deal is “the natural next step” as it will accelerate the time to market for its new B2B product, which provides publishers with a lockscreen SDK that generates additional revenue and enhances engagement.

Buzzvil, founded in 2012, claims to be a market leader in lockscreen advertising in Asia with more than 11 million users from its app, HoneyScreen. In the past, it raised raised $16 million from investors.

According to CEO John Lee: “With our combined scale and geographic reach, we are now positioned to propel lockscreen advertising forward and shape the mobile advertising landscape worldwide.”

Slidejoy will retain its brand and Seo will become the CEO of Buzzvil’s US subsidiary.

The combined company will focus on its apps, Slidejoy and HoneyScreen, as well as expand its publisher base for its B2B offering, BuzzScreen.

As part of the announcement, the company said its first BuzzScreen publisher in the US is an MVNO and it expects to complete twelve more partnerships by the first half of 2017.

Terms of the cash and stock deal were not revealed.