A technological platform responsible for making decisions about what ads to show on a website, serving them, and collecting and reporting data (impressions, clicks, etc).
Ad servers were one of the first pieces of advertising technology introduced to the online advertising industry and are still used extensively by advertisers and publishers.
A publisher’s ad server (first-party ad server) is tasked with filling the ad slots on a website by matching ads from direct campaigns, real-time bidding (RTB) auctions, and other media-buying processes.
An advertiser’s ad server (third-party ad server) tracks the performance (impressions, clicks, conversions, etc.) of the whole campaign across all publishers in a single system, measures the reach of a campaign while taking into account the co-viewership across publishers, and verifies the reports provided by the publishers.