Sellers.json is one of the latest initiatives launched by the IAB Tech Lab in an effort to bring greater trust and transparency to programmatic advertising. It works as a json file hosted by exchanges and SSPs that lists that exchange’s sellers, their information (name, domain), and if the seller is directly or indirectly selling inventory for a publisher’s site. This JSON file can be accessed publicly and will enable buyers to review all the sellers and find information about the final seller of an impression opportunity.