Glossary/Adtech & Programmatic/ads.txt
Adtech & Programmatic
ads.txt
A publicly posted file listing companies authorized to sell a publisher's inventory.
By Brandon Mina·CEO, BrandPilot AI·Updated November 2026
Appears in Lesson 7 of Programmatic 101
Short answer
ads.txt (Authorized Digital Sellers) is a public text file a publisher hosts on its domain listing the companies authorized to sell its ad inventory. Created by IAB Tech Lab, it lets buyers verify that a seller is legitimate before bidding. It helps combat domain spoofing and unauthorized reselling of inventory.