Ad Server

A technological platform responsible for deciding which ads to display on a website, serving those ads, and collecting and reporting performance data such as impressions and clicks.

Ad servers were among the first pieces of advertising technology introduced to the online advertising industry and remain in widespread use by both publishers and advertisers today.

Publisher ad servers (also called first-party ad servers) handle the supply side: they fill a website's ad slots by matching available ads from direct campaigns, real-time bidding (RTB) auctions, and other media-buying processes.

Advertiser ad servers (also called third-party ad servers) operate on the demand side: they track campaign performance — impressions, clicks, conversions, and more — across all publishers in a single system, measure overall campaign reach while accounting for co-viewership across multiple publishers, and independently verify the reports that publishers provide.