What is sellers.json & SupplyChain Object?

Also known as: schain

Quick definition

sellers.json is a file published by an SSP or exchange that discloses the identity of each seller account it represents, while the SupplyChain object in the bid request records every hop the impression passed through; together with ads.txt they let buyers verify the full path from publisher to DSP.

Key points

Seller types: PUBLISHER, INTERMEDIARY or BOTH, with optional confidential flag.
Completeness: schain.complete = 1 means every node up to the originating seller is listed.

Benefits

Exposes hidden intermediaries
Enables data-driven SPO

Trade-offs

Confidential entries limit transparency
Inconsistent IDs across files

FAQ

What is the difference between ads.txt and sellers.json?

ads.txt is published by the publisher and lists who may sell; sellers.json is published by the ad system and states who the sellers are. Buyers cross-check both.

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Official sources

IAB Tech Lab – sellers.json

Last reviewed 2026-10-27. Explanations are written by AdTech Radar; consult the official specification for implementation.

Related terms

ads.txt & app-ads.txt

ads.txt (for websites) and app-ads.txt (for apps and CTV) are public text files hosted by a publisher that list every ad system and account ID authorized to sell its inventory, letting buyers reject unauthorized resellers and domain spoofing.

OpenRTB

OpenRTB is the IAB Tech Lab specification that standardizes how an exchange or SSP sends a bid request describing an impression to DSPs and how DSPs answer with a bid response, so thousands of buyers and sellers can trade in real time through one common JSON message format.

Supply Path Optimization (SPO)

Supply path optimization is the practice of buyers choosing the fewest, cheapest and most transparent routes to the same publisher inventory, cutting redundant resellers so more of the media budget reaches the publisher.