Cross-checking sellers.json removed paths carrying 6% invalid traffic

Cross-checking sellers.json removed paths carrying 6% invalid traffic

sellers.json (a public file where each SSP lists the seller accounts authorized to sell its inventory). One buyer used it to audit supply quality, not just spend.

1. They mapped every winning path's seller ID against the SSP's sellers.json and the publisher's ads.txt.
2. They flagged paths where the seller was listed as 'intermediary' but the chain length in the SupplyChain object exceeded two hops.
— 11% of spend ran through chains of three or more intermediaries.
3. They overlaid invalid-traffic rates from their measurement vendor onto those paths.

Evidence: the long-chain paths carried a 6.1% invalid-traffic rate versus 1.2% on direct and single-hop paths. Blocklisting them cut measured invalid traffic on the line nearly in half and shifted that budget to cleaner supply at a comparable CPM.

Why it matters: chain length in the SupplyChain object correlates with fraud exposure. Each undeclared intermediary is a place provenance breaks. Auditing seller IDs against sellers.json turns an opaque path into a traceable one, and untraceable paths are where invalid traffic hides.