Supply chain · also called DemandChain object
buyers.json
buyers.json is an IAB Tech Lab standard in which DSPs and buying platforms publish a file identifying the buyer accounts ("seats") on their platform, helping sellers see who is really bidding.
buyers.json is the demand-side mirror of sellers.json. A DSP or buying platform publishes a file listing its buyer IDs and the companies behind them. The companion DemandChain object in the bid response records which buying entities passed the bid along, much as the supplyChain object records sellers.
The IAB Tech Lab introduced buyers.json and the DemandChain object around 2021. The goal was to help publishers and SSPs identify the advertiser or intermediary behind a bid, block bad actors, and understand which buying paths bring real demand, supporting demand path optimization and malvertising defence.
Adoption has been far lower than for ads.txt and sellers.json, partly because buyers are wary of revealing client and seat details. Where it is available, it gives sellers another cross-check on who they are dealing with.
Think of it like this
buyers.json is like an auction house asking bidders to register their real names, rather than only showing paddle numbers.
An example
An SSP sees a bid from DSP seat 3021. The DSP's buyers.json maps 3021 to a named agency trading desk, so the SSP can apply that agency's deal terms.
Related terms
sellers.json
sellers.json is a public file in which SSPs and exchanges list their seller accounts, naming who owns each one and whether it is a publisher or an intermediary.
Demand path optimization
Demand path optimization (DPO) is a publisher's or SSP's practice of prioritising the buyers and routes that deliver the most value, and cutting those that add cost without adding demand.
DSP (demand-side platform)
A DSP (demand-side platform) is software that advertisers and agencies use to buy ad impressions automatically across many exchanges and publishers, deciding which impressions to bid on and how much.
SupplyChain object (schain)
The SupplyChain object (schain) is a field in OpenRTB bid requests that lists, in order, every seller or intermediary that handled the impression on its way from the publisher to the buyer.
IAB Tech Lab
IAB Tech Lab is the non-profit standards body for digital advertising technology, founded in 2014, which develops specifications such as OpenRTB, VAST, ads.txt, sellers.json and the Open Measurement SDK.