Abstract: Systems and methods for identifying competitors using content extensions in content items in content items associated with their content placement campaigns are described. A processor identifies one or more competing entities from auctions in which the first entity places a bid. The competing entities are associated with content items having a first type of content extension that received impressions in at least one identified auction. The processor computes an overlap rate based on a number of auctions in which both a content item having the first type of content extension of the identified competing entity and a content item of the first entity received impressions and a number of auctions in which a content item having the first type of content extension of the identified competing entity received an impression and the first entity competed. The processor ranks the competing entities based on the computed overlap rate.