Sellers.json is method for inventory sellers to list which resellers they rely on to increase the demand for their publishers' inventory.
Sellers.json was designed to overcome the weakness of Ads.txt that did not achieve the goal helping buyers understand if a seller was spoofing a publisher domain.
Sellers place a JSON file containing a list of sell-side partners in a well-known location hosted on their domain. Sellers also include in the bid request object a SupplyChain object (i.e. schain) containing the vendor partners they received the bid request from.
The Sellers.json file contains a minimum of four pieces of information:
- Seller ID
- Seller Type (e.g., intermediary)
The Sellers.json file can optionally include a plain text comment
- Comment (e.g., "Reseller Exchange via Exchange Bidding")
The seller type can be "publisher," "intermediary" or "both". The same seller can thus designate whether it is selling its own and operated inventory using the "publisher" label or whether it selling some other publisher's inventory using the "intermediary" label. The publisher can use the "both" label when not disclosing this information. Thus a given organization may thus use multiple seller ids. However, a given Seller ID must be unique to that organization.
The Interactive Advertising Bureau (IAB) Tech Lab launched sellers.json in 2019.
Despite its laudable goal, Sellers.json relies on a centralized licensing scheme for publishers to signal the buyers which organizations are authorized sellers and resellers. The organizational identifiers are managed by a central authority, which often requires a fee to issue the identifier. Current authorities include Trustworthy Accountability Group (TAG) and Dun & Bradstreet. An alternate decentralized approach would be to rely on the public/privacy key each organization already relies on to validate HTTPs, which would eliminate the unnecessary overhead and cost incurred by relying on a central authority to license organizational identifiers.
Given these issues the ecosystem is looking into better forms of signaling throughout the distributed advertising supply chain that supports publishers' businesses.