Advertising transparency gaps affect one third of declared sellers
Declared but Unaccountable: Measuring the Seller-Identity Gap in Advertising Supply-Chain Transparency
Computers and SocietyCryptography and SecurityNetworking and Internet Architecture
Summary
Advertising platforms are supposed to list their authorized sellers in public registries to ensure accountability. The authors found that about one-third of these seller identities are missing from the public records, even though they are declared elsewhere. This missing link, which they call the seller-identity gap, breaks the ability to verify who is truly authorized to sell ad space. Their measurements show that this gap is larger for publishers with many copyright removal requests, suggesting less transparency in those areas.
What this means in practice
- •For advertising platform operators: Identify gaps in seller identity data to improve supply-chain accountability and public verification.
- •For digital ad fraud investigators: Prioritize investigation targets by focusing on publishers with higher seller-identity gaps and related removal requests.
Authors
Tommaso Grotto, Alessandro Cantelli-Forti, Alessio Merlo
Abstract
Public advertising transparency relies on a minimum accountability condition: an account authorized by a publisher in ads.txt or app-ads.txt should appear in the applicable sellers.json registry. When an available registry omits the declared seller ID, the authorization remains visible and machine-readable, but its public verification path breaks. We call this failure the seller-identity gap. We measure the gap using 233.4 million normalized advertising-transparency records and an absent-only, coverage-aware evidence rule. A declaration enters the numerator only when the applicable registry is available and omits its seller ID; unavailable, malformed, confidential, and other non-evaluable states remain separate. The resulting row-level floor is 24.25% in a high-popularity, low-removal reference population and 30.71% among publishers associated with at least 100 copyright-removal requests, a 6.45 percentage-point increase. The gap then remains near one third at stricter cumulative thresholds. Standardizing the populations to common weights over 1,469 shared ad systems reduces the primary contrast to 4.65 points: about 72% remains within systems, while 28% forms a composition-associated residual. We connect these population estimates to recurring seller-account coordinates, byte-identical declaration configurations, and provenance-bearing case packets. We frame this declaration-centered investigative use of public advertising records as Ad Transparency Intelligence: it reconstructs declared supply-chain relationships, identifies where public verification stops, and prioritizes evidence for corroboration without equating correlation with attribution. Advertising transparency supports accountability and investigation only when visible authorizations remain publicly verifiable.