ads.txt

ads.txt (Authorized Digital Sellers) is a plain-text file a publisher hosts at /ads.txt on its domain listing the advertising systems and seller account IDs authorized to sell its inventory, each marked DIRECT or RESELLER, so that buyers can reject bid requests from unauthorised sellers.

IAB Tech Lab's current version is ads.txt 1.1, released August 2022, which added the OWNERDOMAIN and MANAGERDOMAIN variables; the specification is maintained on GitHub, and app-ads.txt 1.0 extends the mechanism to apps and CTV (IAB Tech Lab, ads.txt; ads.txt v1.1 specification). Each data line has four fields: the advertising system's domain, the publisher's account ID in that system, the relationship (DIRECT or RESELLER) and an optional certification authority ID. Variables such as OWNERDOMAIN, MANAGERDOMAIN, INVENTORYDOMAIN, SUBDOMAIN and CONTACT carry metadata.

ads.txt is read with sellers.json and the SupplyChain object. A buyer checks that the asi and sid of the first schain node appear in the publisher's ads.txt, then looks the sid up in that system's sellers.json. Our validator at ads.txt and sellers.json validator performs those checks.

Example:

# news.example ads.txt
ssp-a.example, pub-1001, DIRECT, f08c47fec0942fa0
reseller-b.example, 55521, RESELLER
OWNERDOMAIN=newsgroup.example
MANAGERDOMAIN=salesagent.example, US
CONTACT=adops@news.example

Related: sellers.json, SupplyChain object, SPO, SSP.

Source: IAB Tech Lab, ads.txt 1.1 specification (August 2022) and app-ads.txt 1.0.

1. IAB Tech Lab, ads.txt
2. ads.txt v1.1 specification