Yahoo's move to mobile and Tumblr acquisition are beginning to pay off, CEO Marissa Mayer said at the Goldman Sachs Technology Conference on Wednesday.

The company now has a user base of 575 million monthly mobile users and in the fourth quarter reported $1.26 billion worth of gross revenue and $768 million of pro forma GAAP revenue in mobile.

"We needed to reinvent ourselves to become a mobile application company to make money off advertising," she said. "So now it's a material part of our business, and we have worked hard to build that foundation."

Part of the company's transition to a mobile application company has included focusing on native advertising, which is one of Yahoo's fastest-growing businesses, across all of its products, Mayer said. The company is increasingly leveraging data it collects about users to woo advertisers and strengthen its native products, she said.

"We have some of the best data on our platform, as well as of across our network. We can help advertisers identify particular users and target messages to them," Mayer said.

Advertisers on Yahoo are also increasingly wanting to buy programmatic ads for targeting purposes, she added.

Mayer said she has also been pleased with the Tumblr acquisition. With Tumblr users and Yahoo users combined, Yahoo now has one billion users on its platform, she said.

Tumblr has also helped strengthen the company's mobile strategy, with more than half of its users accessing the platform via their mobile devices.

The company also saw a 10 percent growth in Tumblr's user base in the fourth quarter alone, which was faster than user growth on Facebook's Instagram platform, Mayer said.

Mayer also said that the blogging platform is forecast to drive $100 million to Yahoo's revenue this year.