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Implementing app-ads.txt for Safer CTV and OTT Transactions

Supporting the healthy growth of connected TV (CTV) is top of mind at the IAB Tech Lab. With the events of 2020, adoption and usage of CTV has rapidly accelerated. This means tackling timely opportunities and challenges is essential to creating safe and transparent standards in this nascent space, which is why we devoted attention to the topic through our multi-part series of CTV advertising standards and guidance

The IAB Tech Lab has been working on enhancing CTV standards via the specification v1.0.3 of app-ads.txt, which offers improvements for inventory sharing. This post provides an overview of this initiative and what CTV media owners can expect from the updated specification. 


The public comment period was extended until February 12, 2021 so that you can provide your feedback on the IAB Tech Lab’s ads.txt and app-adds.txt guidance for inventory sharing in Connected TV (CTV) and Over-the-Top (OTT) environments. While the finalized specification is geeky reading, here’s what you need to know to prepare for adoption. 

What is ads.txt and app-ads.txt?

Ads.txt is a simple, flexible, and secure framework that allows media owners to create a public record of Authorized Digital Sellers and declare who is authorized to sell their inventory within web-based transactions. This public record improves transparency for programmatic buyers while making it harder for bad actors to profit from selling counterfeit inventory across the ecosystem. 

App-ads.txt is an extension of the original ads.txt standard and was released in 2019 to combat the same issues within in-application ad inventory, such as in mobile in-application or CTV environments. App-ads.txt allows mobile and CTV application publishers to list the various vendors that are authorized to sell their ad inventory within applications. 

What is inventory sharing and why are changes needed from the current ads.txt and app-ads.txt specifications?  

The growing CTV market introduces a much higher occurrence of complex monetization relationships that make it challenging for the current ads.txt and app-ads.txt specifications to be fully supported in CTV and OTT environments at scale. Within CTV and OTT environments, greater complexity is introduced through the concept of inventory sharing. 

Inventory sharing is when multiple entities may have ownership rights over ad space. For example, a Virtual Multichannel Video Programming Distributor (vMVPD) such as SlingTV, a device manufacturer such as Roku, and programmers (broadcasters or cable networks), such as ESPN, all have a share of the monetization rights since they are all crucial in delivering the content to the end consumer.   

What will change with these updated specifications? 

Prior to these additional guidelines, declaring a relationship in which multiple parties had ownership over ad inventory was difficult and required the content distributor to authorize the content owner in their app-ads.txt file directly, along with the content owner’s authorized sellers. The end result was both the content distributor and the content owner would need to authorize the other party, along with the other party’s full list of partners in their ads.txt and app-ads.txt files, and vice versa. Because those files are always changing, it means more maintenance is required, which is not only expensive but also less secure as the list of authorized sellers grows and is ever-evolving as partnerships come and go. 

With these updates, a programmer will now be able to point to another domain (in our example above, the domain of the content distributor) within their app-ads.txt file so a programmatic media buyer is able to validate the publisher ID contained in the bid request to determine if it’s originating from an authorized seller of the programmer or distributor, simplifying and streamlining the process.

Why is this change important for CTV? 

It’s well understood that bad actors follow the money. That’s why we believe it’s critical to place anti-fraud and enhanced transparency measures at the forefront of programmatic transactions, especially as we see the consumption of CTV/OTT continue to rise. Many industry experts firmly believe that major fraud schemes in 2020 (such as ICEBUCKET or StreamScam) could have been drastically reduced in size and impact if these standards and their best practices were widely adopted and media was only bought from entries within those files. Without their adoption, bad actors in the industry are taking market share away from legitimate media owners by fraudulently using their name and representing that name programmatically. The app-ads.txt inventory sharing initiative returns control to the media owner, allowing them to determine who can and cannot represent their brand programmatically.

What can I do to prepare for adoption? 

During the comment period, we encourage all stakeholders in CTV advertising to review the specs and provide feedback — especially on any gaps that we should consider. 

Once the final specifications are published (usually a few weeks after public comment), media owners, CTV platforms, device manufacturers, and content apps all have some steps to take; please refer to the Explainer for details and use cases.

In the meantime, media owners can familiarize themselves with the following best practices: 

  1. If you are the creator or curator of an ads.txt file, the primary best practice is to only list platforms and seller IDs within that file that you can directly attribute revenue to
  2. Do not list any unknown or unrecognized entries, as it opens up the opportunity for bad actors to misrepresent your name and divert market share that would otherwise go to you.

The final version of the standard (IAB Tech Lab’s ads.txt and app-adds.txt guidance for inventory sharing in CTV and OTT environments) will be available soon, so make sure to comment now if you have any input and to account for adoption in your roadmap. 


Neal Richter
Chief Scientist