An ad exchange is a technology platform that facilitate the bidded buying and selling of online media advertising inventory from multiple ad networks. The approach is technology-driven as opposed to the historical approach of negotiating price on media inventory. This represents a field beyond ad networks as defined by the Interactive Advertising Bureau (IAB), and by advertising trade publications such as Advertising Age.
The major ad exchanges include:
- AdECN, which is owned and was purchased by Microsoft in August, 2007 (Microsoft officially switched from AdECN to AppNexus for its real-time bidding needs- three years after it acquired it) This change finally retired the AdECN platform.
- Right Media, which is owned and was purchased by Yahoo! in April 2007;
- DoubleClick Ad Exchange, which is owned by DoubleClick, a Google subsidiary purchased in May 2007;
Ad exchanges can be useful to both buyers (advertisers and agencies) and sellers (online publishers) because of the efficiencies they provide.