Just a day after laying off groups of employees from its content business, Yahoo CEO Marissa Mayer shifted her focus to mobile, underscoring the company's commitment to continue growing its mobile business going forward.

During her keynote speech at Yahoo's Mobile Developers Conference on Thursday, Mayer touted some of the growth numbers the company's mobile business saw last year, and asked developers to keep working on Yahoo's platform.

Yahoo now has over 600 million monthly users on mobile, more than half of its 1 billion total users, helping generate a little over $1 billion in mobile alone, Mayer said. The Yahoo App Publishing platform, which launched last year, is already on a $200 million revenue run rate, while Flurry, its mobile-app monetization and analytics platform, now has more than 800,000 apps working on top of it.

"From growing the Flurry community to turning apps into real businesses, it's been an incredible year. We're proud to be partners with you and excited to grow this together," Mayer said.

Mobile has been a big focus area for Mayer since she joined Yahoo in 2012. She spent hundreds of millions of dollars to acquire ad companies like Flurry and Brightroll, and retooled some of the old apps like Yahoo Weather with Flickr integration to attract more users. Mobile revenue went from $768 million in 2014 to $1.1 billion last year, representing over 20% of Yahoo's total annual revenue.

Today's event comes at a tough time for Yahoo. On Wednesday, Yahoo announced that it would close nearly half of its content verticals, representing a shift away from Mayer's earlier plan to create online "magazines" to grow its users. Some of its top editors, such as Yahoo Tech's Dan Tynan and Yahoo Beauty's Bobbi Brown, left the company as part of the change.

The layoffs are part of Yahoo's cost-cutting plan to cut 15% of its workforce, or roughly 1,600 employees, and close a number of different businesses by the end of the year. One employee who was laid off told The New York Times that the office was like a "blood bath" with all the job cuts announced on Wednesday.

Despite Yahoo's focus on mobile, some reports indicate that its user growth may not be as fast as it's expected to be. According to The Information, mobile daily active users for its three core products — Yahoo Mail, Yahoo Search, and Yahoo.com — have mostly gone down, although individual apps like Tumblr and Yahoo Sports saw big growths.