Today blog network Tumblr announced the rollout of mobile advertisements in its iOS and Android apps. The spots come from six partners: ABC Entertainment and ABC Family, GE, Pepsi and Warner Bros. Tumblr users on mobile will see up to four ads per day, which are distinguished from normal posts using an animated dollar sign ($) icon above each post. The ads launch today, but may not reach every mobile user until the end of May, Tumblr says.

Tumblr hopes that its new ads will feel like the average fare you might see reblogged by friends

Tumblr hopes that its new ads will feel like the average fare you might see reblogged by friends, though they will be inherently more obtrusive than the company's current "Radar" ads on desktop. GE's first ad, for example, features an animated GIF of a jet engine. "The content our brand partners have created is more than just advertising — it is thoughtful, beautiful, and diverse content that fits seamlessly alongside the best work on our network," says Tumblr founder and CEO David Karp. The company plans to bring big "feed" ads to desktop at some point in the future. It's unclear if the feed ads will replace Radar ads, which currently inhabit a small box in Tumblr's right rail.

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Tumblr's new ads launch amidst increasing pressure for the New York startup to show strong revenue growth, and apparently this is just the beginning. Tumblr recently poached Lee Brown from Groupon, where he oversaw a period of massive revenue growth, to be its Global Head of Sales. Brown said, regarding today's news: "This is the first of many exciting planned Tumblr ad launches in 2013." He also said last month that he expects Tumblr to reach profitability some time in 2013. Another possible avenue for growth is letting users promote posts, which the company says it has experimented with. It's tough to tell if promoted user posts have been a successful route for Facebook, but in the ever-changing world of advertising, Tumblr won't rule anything out.