Microsoft has acquired ad inventory management firm Rapt.

Rapt enables publishers to analyze the performance of real estate on their sites, then decide how best to monetize them. Rapt also gives recommendations on whether to sell spots in-house or use a third-party ad network, based on past performance.

The Rapt acquisition is one in a constellation of actions Microsoft has taken to broaden the reach of its ad sales. It recently debuted its own brand engagement tool on Atlas, which — incidentally — will absorb Rapt's software in the Microsoft family.

Last week Google announced Ad Manager, a free online ad inventory management system built on DoubleClick technology. It performs similar services as Rapt, with less of a track record. Rapt's professional relationships include pairings with Publicis and NYTimes.com.