App-ads.txt release from IAB Tech Lab: what's in for you?

The Interactive Advertising Bureau Technology Laboratory (IAB Tech Lab) has released the app-ads.txt standard. We break down what this means for you.

What is the IAB Technology Laboratory?

The Interactive Advertising Bureau (IAB) is an advertising organization that develops industry standards, conducts research, and provides legal support for the online advertising industry. Its tech branch, the IAB Technology Laboratory, helps companies implementing those technical standards by reducing the friction with the interpretation of technical protocols, tests their platforms and evaluates compliance to IAB standards. IAB Tech Lab founding members includes companies like AppNexus, Google, PubMatic, and Yahoo.

What's the big news?

So far, the “ads.txt“ has been a standard only available on the web. “Ads.txt” stands for Authorized Digital Sellers that allows publishers (i.e. owner of a website) to publicly declare the companies they authorize to sell their digital inventory (i.e. sell ads on their websites).

Why this? When an advertiser buys media programmatically, he expects the URLs he purchased were legitimately sold by those publishers or their distributors (as we have seen, the owner(s) of a website). However, a buyer cannot easily check who is responsible for selling those impressions across exchanges! While every impression already includes publisher information from the OpenRTB protocol, there is no way to confirm the validity of the information sent in the RTB bid request itself, leaving the door open to counterfeit inventory.

With “ads.txt” a buyer receiving a bid request claiming to be a certain website, let’s say “”, can verify if the exchange and SellerAccountID (also part of the bid request) are matching the authorized sellers listed in “” file (which is controlled by the owner of the website) by simply crawling it (note: better crawl it offline than in real-time!).

So, this tiny file increases transparency in the programmatic ad-ecosystem. And now it is finally available for mobile apps as “app-ads.txt”, hopefully reducing all those ad-frauds happening on mobile ads!

App-ads.txt & 42matters, what it means for our customers

The “app-ads.txt” works in a very similar way to “ads.txt”, but it relies on the app store’s web-page of a given app to find the legitimate publisher’s website/domain.

In a nutshell, programmatic bid requests will involve these steps:

  1. An exchange receives a bid request from a certain app (e.g. a user is generating an ad-impression) and notifies media buyers.
  2. In the bid request (as per OpenRTB standard) the app will be identified by its “Bundle ID” (usually as it is seen by the mobile operating system) and the mobile OS by the “Store ID”. For example for “The Weather Channel” on Android the “Bundle ID” would be:
  3. The buyer can now easily find the app store page of that app, in our example:
  4. In the meta-data or content of the page, the buyer can now read the legitimate website/domain of the app (as entered by its owner). In this example:
  5. Buyer can now crawl the “app-ads.txt” to look for the authorized media sellers for the app. In our example the tiny file will be located at: 

Unfortunately, this approach requires an additional step on the programmatic buyer side (i.e. step 3), but also requires a programmatic buyer to keep the data consistent and up-to-date for millions and millions of apps across multiple app stores. Not that easy…

At 42matters, we manage all above steps for you, we aggregate “app-ads.txt” files for all apps, and we keep this data up-to-date on a weekly basis as per IAB guidelines. Our aggregation service can be accessed via a volume-based API, or in bulk via File Dumps (also as an Excel .csv file).

Are you interested in saving time and resources while accessing the highest-quality “app-ads.txt” data? If yes, then feel free to contact us, we already support hundreds of companies working in ad-tech and we will be glad to help you as well!

‍References and useful links: