AppNexus Raises A Meaty $50 Million Series C For Realtime Ad Bidding Platform

Realtime ad bidding network AppNexus today announced that it raised $50 million in a Series C financing. Investors include Microsoft, Venrock, Kodiak Venture Partners and First Round Capital. The round brings the total capital raised by AppNexus since its founding to $65.5 million. The company first raised an angel round in 2007 from Ron Conway, Marc Andreesen, Ben Horowitz, Khosla Ventures, and First Round Capital.

AppNexus is based in New York City, and was founded by Brian O’Kelley, who was also a co-founder of Right Media. (Yahoo purchased Right Media in 2007 at an $850 million valuation).

AppNexus calls itself a realtime bidding platform for ad networks. It allows 120 ad networks to interface with the big online display advertising exchanges such as Google Ad Exchange (formerly DoubleClick Ad Exchange), Microsoft Media Network, Admeld, OpenX, and AdECN, helping the ad networks bid for display ad spots across the Internet. “We exist to drive demand to the ad exchanges,” says O’Kelley.

More than 4 billion ad impressions are served through AppNexus every day, up from zero two years ago. AppNexus is a software company that builds the interfaces and management tools for the ad networks to interface with the ad exchanges, ultimately allowing advertisers to better optimize for cost-per-clicks, cost-per-impressions, and other metrics.

While he won’t disclose specific details, CEO O’Kelley tells me, “We’ve gone crazy on the revenue side in the past year.” He’s also been hiring, going from 23 employees at the beginning of the year to about 65 today.