A bid request can now name everyone who touched it

The revenue mechanism

Ads.txt let a buyer confirm which companies a publisher had authorized to sell its inventory, but it stopped there: a bid request could still pass through several resellers between the publisher and the final buyer without naming any of them. The sellers.json specification page records that the OpenRTB Working Group "finalized the specifications for industry adoption on July 31, 2019" for two companion documents: sellers.json, a file each advertising system publishes listing the entities it works with, and the SupplyChain object, a field added to each bid request that lists every intermediary node that touched it. Together they let a buyer trace a bid back through the chain of resellers to the domain that originally sold it, which is the mechanism that determines how much of an advertiser's spend a publisher actually keeps versus how much is absorbed by intermediaries along the way.

What the documents show

The same page states plainly what the earlier standard could not do: the ads.txt specification "does not however make any attempt at revealing the identities of the publisher account IDs" inside an advertising platform. Sellers.json closes that gap by publishing, for each seller ID, whether it belongs to a publisher directly or an intermediary, cached so it need not be repeated on every bid request. The supply chain standards listing, current as retrieved on 16 September 2026, shows the SupplyChain object was still being revised three years later, reaching version 1.1 in August 2022, confirming this is a maintained standard rather than a document frozen at its 2019 release.

The assumptions exposed

These specifications assume that every intermediary in a chain actually publishes an accurate sellers.json file and correctly populates the SupplyChain object on each request; neither document can force a non-compliant company to comply. Visibility into who touched a bid request is not the same as a guarantee that each of those companies is trustworthy or fairly priced. A publisher can also over-read "SupplyChain compliant" as meaning a short, cheap path to the buyer, when a technically compliant chain can still include several resellers each taking a margin before the money reaches the publisher.

What to check before you rely on it

This is an editorial checklist, not IAB guidance. A publisher weighing a demand partner's claims about a "direct" or "short" supply path should ask for the actual chain, not just a compliance statement.

• How many nodes typically appear in the SupplyChain object for your inventory, and who are they?
• Does your sellers.json entry correctly mark your account as belonging to you rather than a reseller?
• Is a partner's "supply path optimization" claim backed by chain data, or only by their own description?

The specifications make the supply chain visible in principle; whether a publisher's actual partners populate that visibility honestly is a separate, ongoing question the documents themselves cannot answer.