What is sellers.json?

sellers.json is a JSON file that an advertising system, such as an SSP or exchange, publishes on its root domain to list its sellers, identifying each by seller ID, seller type and, unless confidential, name and domain.

Also known as: sellers json

How it works

ads.txt tells buyers which seller accounts a publisher has authorized, but an account ID on its own says nothing about who is behind it. The IAB Tech Lab notes that ads.txt does not try to reveal the identities of those account IDs, and sellers.json fills that gap (IAB Tech Lab).

An advertising system hosts the file at /sellers.json on its root domain, ideally over HTTPS. The file has a version field and a sellers array, plus optional contact details and identifiers such as a TAG-ID or DUNS number. Each seller entry includes (sellers.json specification):

  • seller_id (required): the same ID that appears in ads.txt and in the sid of a SupplyChain object node.
  • seller_type (required): PUBLISHER, INTERMEDIARY or BOTH.
  • name: the legal entity paid for the inventory, required unless the seller is confidential.
  • domain: the seller's root domain, required where the seller has a web presence and is not confidential.
  • is_confidential and is_passthrough (optional): flags for confidential sellers and for certain account-control relationships.

An illustrative entry, using placeholder values, looks like this:

{
  "seller_id": "10001",
  "seller_type": "PUBLISHER",
  "name": "Example News Media Ltd",
  "domain": "examplenews.example"
}

How does it fit with ads.txt and the SupplyChain object?

The three standards answer different questions. ads.txt, published by the publisher, says who is allowed to sell. sellers.json, published by the advertising system, says who each seller account belongs to. The SupplyChain object, carried in each bid request, says which accounts handled this particular impression. With all three, a buyer can identify the final seller of a request and every node in its chain. Because buyers can look identities up and cache them offline, bid requests do not need to carry the same details every time (IAB Tech Lab).

Why it matters

For buyers, sellers.json turns an anonymous ID into a named company, which supports supply path optimization and makes it easier to spot unexpected intermediaries. For publishers, it is worth checking how they appear in their partners' files. A wrong seller type or a mismatched domain can make a direct relationship look like a resold one.

Example

Example (illustrative)

A buyer sees a bid request whose ads.txt check passes for account 10001 on an exchange. It looks that ID up in the exchange's sellers.json and finds a PUBLISHER entry with the same domain as the site in the request. That match gives the buyer more confidence it is buying directly from the owner.

IncrementX perspective

Transparency is part of representing inventory well, because buyers increasingly favour routes they can verify. For publishers working with a representation partner, the practical step is to make sure that their ads.txt lines, the partner's sellers.json entries and the bid requests all tell the same story. Read more about how this fits into media representation.