The Programmatic Glossary
A practical glossary designed to help marketers, advertisers and ad-tech professionals understand the terminology that powers programmatic advertising
Supply Chain Transparency
Ads.txt (Authorised Digital Sellers)
A simple text file that publishers place on their website to publicly declare which companies are officially allowed to sell their advertising inventory. It is a transparency tool that helps buyers verify they are purchasing legitimate inventory and not fake or misrepresented supply.
HOW IT WORKS
A publisher creates a file called ads.txt and hosts it on their domain (e.g. publisher.com/ads.txt). Inside the file, they list every supply-side platform (SSP), ad network, or exchange authorised to sell their ads. Before buying, demand-side platforms (DSPs) and buyers can check this file to confirm the inventory is legitimate.
EXAMPLE
The Guardian publishes an ads.txt file listing authorised partners including Google, Xandr and Magnite. If a fraudster tries to sell fake 'Guardian' inventory through an unlisted exchange, any buyer who checks ads.txt will see the fraud and reject the bid.
RELATED TERMS
sellers.json | Supply path optimisation (SPO) | Domain laundering | Supply-side platform (SSP)
★ LIMELIGHT INSIGHT: Limelight requires all publisher partners to implement ads.txt as part of its supply quality standards, ensuring buyers can verify every impression in the platform.
