Yahoo has roughly 800 million monthly active users across its core sites, Mayer said Tuesday, and about 400 million of them are active on mobile devices.
If Yahoo can get more daily users on mobile, it could help it to expand its advertising revenue.
Mayer talked at length Tuesday about Yahoo's efforts around "native advertising," in which advertisers provide content that looks like editorial content. She also talked about its programmatic ad-buying technologies, which can target ads based on user data.
Getting more data from mobile apps could help Yahoo in both these areas, she suggested.
"If you're a brand advertiser, the notion to get your brand on a two-by-three inch screen and see the interaction with that brand on a daily basis ... the opportunity is huge," Mayer said.
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