Definition of Media Metrix

Internet audience measurement firm that tells advertisers which web sites a sample audience is accessing and the characteristics of the audience, much as ACNielsen Company measures television audiences; also called web rating service. Media Metrix uses a sample consumer panel to track their Internet activity and project it out to the total Internet user population. Media Metrix is currently the only ratings service that includes workplace users, but very few are represented in their sample. Unlike other advertising media, the Internet makes immediate response measurement possible as well as immediate revisions to a campaign. Other web rating services include the Nielsen NetRatings joint venture.