Wiki · Concept · Last reviewed June 25, 2026

Sellers.json

Sellers.json is an IAB Tech Lab standard that lets advertising systems publish machine-readable information about the sellers and intermediaries in the programmatic advertising supply chain.

Category: Concept / Ad Tech Published: June 25, 2026 Modified: June 25, 2026 Last reviewed: June 25, 2026 Tags: sellers.json, adtech, real-time bidding, supply chain, privacy, platform governance

Definition

Sellers.json is a supply-chain transparency standard for programmatic advertising. IAB Tech Lab finalized the specification on July 31, 2019 and describes it as a way to increase trust on the supply side of real-time bidding and programmatic buying. The file is a JSON document, normally hosted at a public /sellers.json location by an advertising system, that identifies entities involved in selling or reselling digital advertising inventory.

The standard belongs beside Real-Time Bidding, Data Brokers, and Surveillance Capitalism because it exposes part of the market plumbing behind a page view. A user sees a page or app. An advertiser sees an impression opportunity. The supply chain may include publishers, exchanges, supply-side platforms, resellers, and intermediaries. Sellers.json tries to make some of those roles inspectable.

It is not a privacy guarantee, consent record, audit, or regulator approval. It names seller identities and relationships in a standard format. It does not prove that bidstream data was minimized, that every recipient had a lawful basis, or that the person whose attention was auctioned understood the chain.

Mechanism

A sellers.json file includes a required sellers array and a required version string. Each seller object can include a seller identifier, seller name, domain, seller type, confidentiality status, and related metadata. The specification defines seller types such as publisher, intermediary, or both. It also says the seller identifier should map to one entity and should be consistent with other adtech identifiers where applicable.

Sellers.json is meant to work with two adjacent standards. ads.txt lets a publisher publicly list authorized digital sellers for its inventory. The OpenRTB SupplyChain Object lets a bid request carry a chain of nodes describing entities involved in selling or reselling an impression. Sellers.json gives buyers a place to resolve the opaque identifiers in those chains into named business entities.

The result is a cross-check, not a full map of reality. If an exchange receives a bid request with a SupplyChain Object, a buyer can inspect the relevant advertising-system domains and seller identifiers, then compare the chain against sellers.json and ads.txt evidence. Missing files, confidential entries, stale records, unusual reseller paths, and unexplained intermediaries can become review signals.

Agent Context

For AI governance, sellers.json is useful because agents and automated buying systems need evidence about who is asking for money, data, or attention. A media-buying agent, brand-safety agent, compliance crawler, or publisher audit tool can use sellers.json as one input when deciding whether an ad path looks authorized, unusually indirect, or hard to explain.

The same pattern applies beyond advertising. Machine-readable supply-chain disclosures are increasingly used to decide whether software packages, model components, data providers, and infrastructure vendors can be trusted. Sellers.json is an adtech example of that wider discipline: publish the parties, make the identifiers resolvable, and keep the record open enough for outsiders to test.

Governance Use

A governed advertising or AI-assisted marketing program should record the sellers.json URL, retrieval time, file hash, advertising-system domain, seller IDs, seller types, confidentiality flags, SupplyChain Object nodes, ads.txt entries, and any discrepancy review. If a buyer excludes unknown sellers, reseller-heavy paths, confidential entries, or missing domains, those policy rules should be explicit and versioned.

Controls should also connect supply-path transparency to privacy review. A clean seller chain does not answer whether a bid request contained precise location, sensitive page context, identifiers, or inferred audience segments. The governance record should therefore pair seller-path evidence with field-level bidstream review, retention limits, contractual use restrictions, and deletion pathways.

Limits

Sellers.json can expose the business chain without exposing the data chain. It may tell a buyer which companies were in the path, but not what each company received, retained, enriched, brokered, modeled, or deleted. A legitimate-looking chain can still carry excessive data. A valid seller entry can still participate in manipulative targeting, discriminatory steering, or weak consent flows.

The standard also depends on publication quality. Files can be stale, incomplete, misconfigured, or intentionally opaque through confidential seller entries. Buyers may not check them. Intermediaries may change faster than review processes. Smaller publishers may rely on complex reseller paths they do not fully understand. Transparency infrastructure only works if someone reads it, logs it, and treats anomalies as operational events.

Source Discipline

Claims about sellers.json should cite IAB Tech Lab materials and identify whether the claim concerns the sellers.json file, the OpenRTB SupplyChain Object, or ads.txt. Those are related standards with different jobs. Claims about privacy, consent, competition, or data protection require separate legal and empirical sources; sellers.json itself is not evidence that the auction was lawful or fair.

Spiralist Reading

Spiralism reads sellers.json as a ledger at the edge of attention. It admits that the ad market is not a simple meeting between publisher and advertiser, but a chain of institutions around a moment of perception. The useful ritual is not "trust the standard." It is "follow the chain, name the parties, and refuse to let invisible intermediaries become normal."

Sources

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