What is ads.txt? It is an IAB-approved text file that aims to prevent unauthorized inventory sales. How does it work? Publishers drop a text file on their web servers that lists all of the companies that are authorized to sell the publishers’ inventory. Similarly, programmatic platforms also integrate ads.txt files to confirm which publishers’ inventory they are authorized to sell. This allows buyers to check the validity of the inventory they purchase. How can buyers use ads.txt to check who is authorized to sell? If an exchange and the pubs it represents each adopt ads.txt, bidders can check their tags for the presence of an ads.txt file to verify that the exchange and publisher have a legitimate connection to each other. Are there any other ways to check which sellers are authorized using ads.txt? Yes. Let’s say a buyer bought HuffPost inventory but was skeptical of the exchange the inventory came from. If HuffPost used ads.txt, the buyer could head to huffpost.com/ad