• by Mark Walsh  @markfwal, April 22, 2013

Tumblr on Monday rolled out advertising in its mobile app after announcing plans to do so in March. The blog network launched advertising on the desktop almost a year ago.

Tumblr told Ad Age people using its iOS and Android apps will see up to four ads a day in their streams, with a "sponsored" label and dollar-sign icon in the right corner to set them apart from other posts. However, people can like "like" or reblog ads as they can with any other post.

The company plans to extend the in-stream ads to the desktop version but gave no timetable for the rollout. It currently shows ads in the Radar and Spotlight sections of the site, which hosts more than 100 million blogs and adds more than 90 million posts a day.