At a conference in San Francisco Wednesday, Yahoo CEO Marissa Mayer announced that the Web-media company’s audience has passed 800 million monthly active users. These numbers don’t include traffic from Tumblr, a blogging network which Yahoo acquired earlier this year. Mayer said that 350 million of those users use Yahoo on mobile, and that the growth came primarily from increased usage of its homepage, news, email, and search tools. 

These numbers reflect 20 percent growth since July 2012, when Mayer took over as CEO.

Mobile Priorities

While the core growth seems promising, Mayer told interviewer Michael Arrington at the TechCrunch Disrupt conference that she’s focused on the company’s mobile services. 

“In terms of brand need, a big piece is mobile,” Mayer said. “What Yahoo has always been strong in, mail, news, and finance … that’s what people do on their phones.”

Headcount on Yahoo’s mobile team has grown by a factor of 10 since Mayer’s arrival.

The company also revamped its email services, including redistributing inactive email addresses.

Mayer, who previously worked as an executive at Google, talked about her own experience using Yahoo Mail, describing the product as fast and efficient. 

She noted that it doesn’t have video chat or other services that competitors like Gmail provide, and it might not in the future, either.

“We may experiment with it, but might get in the way of using mail everyday, and we want it to be efficient,” she said.

Spending To Make Money

Yahoo’s market capitalization has grown by $14 billion over Mayer’s tenure, an increase she attributed to the increased value of Yahoo’s investments in Yahoo Japan and Alibaba, a Chinese Internet company.

Yahoo’s booming stock price and cash from selling some of its holdings in Alibaba have helped Mayer make a host of acquisitions, from the $1.1 billion Tumblr deal to a number of smaller startups.

Since most of Yahoo’s growth seems to have come from its core products, not new ones, it’s hard to quantify the payoff from those deals.

But Mayer said she’s trying to create a “chain reaction” to turn around Yahoo that starts with “people”—the talent she’s brought in through these deals and through hiring—and then leads to better products. Better products result in better traffic, and ultimately revenues, she argued.

So her turnaround remains a work in progress. But with its latest growth numbers, there are signs that it’s working.