sellers.json

Foundational IAB Tech Lab open standard for programmatic supply chain transparency, widely adopted across the global AdTech ecosystem

sellers.json is an open technical standard developed and maintained by the IAB Tech Lab, published in 2019 as part of a broader suite of supply chain transparency initiatives in programmatic advertising. The standard requires ad systems — including SSPs, exchanges, and ad networks — to publish a publicly accessible JSON file at a standardized URL path that lists all sellers (publishers, intermediaries, and resellers) they represent. Each entry includes a seller ID, seller name, domain, and seller type, enabling buyers to verify the legitimacy of inventory sources. The sellers.json standard works in concert with ads.txt (Authorized Digital Sellers) and the SupplyChain object (OpenRTB extension) to create an end-to-end verifiable chain of custody for programmatic ad impressions. While ads.txt allows publishers to declare which platforms are authorized to sell their inventory, sellers.json provides the complementary view from the supply-side platform's perspective, and the SupplyChain object ties individual bid requests to the full chain of entities involved in a transaction. Together, these tools significantly reduce ad fraud, domain spoofing, and unauthorized reselling. As an IAB Tech Lab standard rather than a commercial company, sellers.json has no revenue model, employees, or headquarters in the traditional sense. Its significance in the AdTech ecosystem is profound: it has been widely adopted by major SSPs, exchanges, and ad networks globally, and is considered an industry baseline for supply chain transparency and brand safety compliance. Adoption is monitored and encouraged by buy-side platforms, DSPs, and agency trading desks as a prerequisite for trusted inventory sourcing.