Ads.txt
From Just Solve the File Format Problem
Ads.txt is a special file promoted by the Interactive Advertising Bureau (IAB, not to be confused with the Internet Architecture Board) to let a site announce its officially endorsed ad networks and the associated account IDs in order to prevent fraud. It is placed in the root directory of a site similarly to robots.txt. The filename in actual use is all-lowercase, ads.txt, but the spec refers to the standard as the capitalized Ads.txt. There is also a related spec for an "Authorized Sellers for Apps" file, app-ads.txt.
