sellers.json provides a mechanism to enable buyers to discover who the entities are that are either direct sellers of or intermediaries in the selling of digital advertising.
A published and accessible sellers.json file allows the identity of the final seller of a bid request to be discovered (assuming that they are ads.txt authorized). It also allows the identities of all nodes (entities that participated in the bid request) in the SupplyChain object to also be discovered. Currently, it is possible for the final seller to be identified via the Publisher.name and Publisher.domain attributes, but in practice, these properties are inconsistently populated by various selling systems. sellers.json enables smaller bid request object sizes by allowing this information to be looked up and cached “offline” rather than supplied with every bid request. sellers.json also allows the identification of any and all intermediaries that participated in the selling of a bid request.