sellers.json

sellers.json is the SSP-side companion to ads.txt. It's a JSON file served at the SSP's root domain (e.g. ssp.example.com/sellers.json) that declares every account ID the SSP knows about and links each one to a seller — either a publisher (DIRECT) or another SSP (INTERMEDIARY). A DSP combines the two files to verify that the bid request's claimed supply path is real end-to-end.

The IAB Tech Lab released sellers.json in 2019, two years after ads.txt, to close the symmetric gap. Without sellers.json, a buyer could verify that publisher X authorized SSP Y, but couldn't verify that SSP Y in turn was authorized to relay through SSP Z. The full chain is reconstructable from the SupplyChain Object (schain) in the bid request, with each hop verifiable against the upstream party's sellers.json.

In practice, most fraud-prevention happens at the schain check. A DSP that sees a 5-hop schain where hop 3 isn't in hop 2's sellers.json knows the chain is forged or stale, and won't bid. Sites and networks that don't expose sellers.json get downweighted.

Trillboards exposes its sellers.json at trillboards.com/sellers.json. The SSP side of our platform is named "Adipolo" in our public declarations to protect partner relationships — see the variant-code mapping in the partner SDK docs.