The ads are a mobile-enhanced version of Tumblr Radar, the blogging platform's take on sponsored content. The units are similar to Twitter's promoted tweets or Facebook's sponsored stories in that the advertised content is native to the platform.
The mobile ad addition comes roughly a year after the 6-year-old company first started selling ads. The front-and-center placements suggest that Tumblr is ready to make good on a promise to become profitable.
With the launch, Tumblr is, for the first time, making its advertisements unavoidable as content that flows through the stream. Previously, members only saw ads to the right of the dashboard and in the Spotlight section of Tumblr's desktop experience.
Beginning Monday, mobile users will see sponsored Tumblr stories that are denoted by the "sponsored" label and a dollar sign icon, as pictured above. An ad for the upcoming Warner Bros. flick "The Great Gatsby", for instance, features Leonardo DiCaprio in animated GIF form. The text of the content ad reads: "Prepare for the Summer of Gatsby - in theaters May 10," and encourages viewers to follow the gatsbymovie Tumblr. People can reblog or "like" the post as they would any other Tumblr update.
Tumblr powers more than 100 million blogs and sees more than 90 million posts created each day. Members spend, on average,, according to CEO David Karp.