Following multiple cases of fraud involving improper maintenance of ads.txt, IAB Tech Lab has taken a step forward to streamline regular validation of publishers’ (app)ads.txt files – using the automated Supply Chain Validation.

Four Years of Ads.txt: There’s Still Room for Improvement

Back in 2017 when IAB initially introduced the ads.txt initiative, it primarily aimed to provide buyers with more confidence in publishers’ inventory, and that it achieved, at least to some extent.

However, even in spite of the subsequent release of sellers.json and buyers.json specifications, the overall transparency across the programmatic supply chain hasn’t reached the desirable threshold until today. 

More importantly, the ads.txt specification turned out to have significant vulnerabilities, often exploited by fraudsters. Add it to frequent issues with incorrect maintenance of ads.txt files, and the success story of ads.txt no longer looks cloudless.

On the bright side, however, over the past few years IAB Tech Lab has been continuously working on ways to streamline the implementation of ads.txt and mitigate fraud risks. 

Namely, one of the initiatives is the deprecation of support of empty ads.txt files in March 2020. That is, it’s currently required to add at least one properly formatted line to declare that the file adheres to the specification guidelines, in case no ad system is authorized to sell a publisher’s inventory:, placeholder, DIRECT, placeholder.

And another one is known as the automated Supply Chain Validation service.

What is Automated Supply Chain Validation?

Introduced in May 2021, Supply Chain Validation by IAB Tech Lab implies regular automatic checks of publishers’ (app)ads.txt files for possible errors and their validation against existing sellers.json files. 

The service also implies sending email notifications in case any inconsistencies and/or errors are found, and publishing of the validation results for buyers’ ongoing review. 

The validation process includes a number of standard test cases, run automatically (without any prior notice to a publisher) for each seller’s entry in their ads.txt. In particular, the scope of test cases includes, among other things:

  • accessibility of ads.txt (e.g.request timeouts, internal and external domain redirects); 
  • file formatting (e.g. file content type, check for syntax errors);
  • ad system domain validation;
  • validation against direct sellers’ and resellers’ sellers.json files.

Why & How to Apply for Automated Supply Chain Validation

One of the key benefits of the automated supply chain validation for publishers is its ability to help them streamline ongoing checks of ads.txt files, hence minimizing formatting errors and mitigating risks of the potential unauthorized sale of their inventory. 

More importantly, it also enables publishers to keep their representation in partners’ sellers.json files under control, hence sustain their reputation in the marketplace.

Meanwhile, one of the possible downsides of the newly-introduced service is its price. According to IAB Tech Lab, the current minimal fee per one domain is $99/year, with possible discounts (however, unspecified ones).

As for the application process, it’s fairly straightforward and implies a publisher’s subscription to the service via the IAB Tech Lab portal at