We already have ads.txt to authenticate sellers of web-based ad inventory. But what about the app-based inventory? On March 13th, IAB released the final version of app-ads.txt for mobile apps and OTT services.

The idea of implementing app-ads.txt is the same as ads.txt—listing down the names of authorized inventory sellers. However, the technicalities are different which may confuse publishers, sellers, and buyers during implementation.

What is App-ads.txt?

app-ads.txt (Authorized Sellers for Apps) is an IAB-initiative through which mobile app publishers can declare vendors they have authorized to re-sell their inventories. By referring to app-ads.txt, buyers can check whether or not the vendors offering inventory are authentic.

Adding an open list like app-ads.txt contributes to a more transparent supply chain and minimizes the risk of ad fraud practices such as app spoofing. This technology is an effort to save app publishers from ad fraud by listing authorized sellers.

app-ads.txt is a publically available file that can be accessed by DSPs and advertisers. Just like ads.txt, app-ads.txt is not mandatory (yet), but a recommended practice.

Why Not Just Use Ads.txt?

Websites and applications are considered to have different inventories. Web-based ad inventory sellers typically don’t deal with an app-based inventory. Keeping that in mind, both types of inventories needed separate files declaring their respective authorized sellers.

In short, just like for web inventory, mobile app inventory requires its own spec to authorize sellers and prevent fraud. Hence, app-ads.txt offers the same to app and OTT publishers.

What Does The App-ads.txt File Contain?

Similar to ads.txt, app-ads.txt can also be created using a text editor; remember to save the file with ‘.txt’ extension. Here are the details you need to create a list of authorized sellers for app:

  • Seller’s domain name: As the name suggests, this is the domain name of the seller. For instance, if you use MoPub to monetize your app inventory, then the source domain would be mopub.com.
  • Publisher/Seller ID: If the publisher is a direct seller of his own inventory, then the publisher ID will have to be added to the list. In the case of resellers, their seller ID would be needed.
  • Type of relationship: The publisher-seller relation needs to be defined. Sellers having direct contact with publishers would be direct sellers. Whereas, sellers getting inventory from SSPs or ad exchanges would be considered resellers. In some cases, a seller can be both, a direct seller and reseller.
  • Ad source ID: This refers to the TAG ID of the seller stating the seller or his company is compliant with the best (fraud-free) practices of ad tech.

These details must be written in CSV (Comma Separated Values) format. Here’s how it should look like:

mopub.com, [Publishers/Seller ID], DIRECT, 74b46c0ea83967ca

How Does app-ads.txt Work?

Along with a mobile application, app publishers also usually have a developer website. The app-ads.txt file is uploaded to this website. Here, buyers will find the list of authorized sellers at ‘domain.com/app-ads.txt’.

app-ads.txt is published and hosted in the same way as ads.txt. The app publisher will create a text file with the details of all the authorized sellers and host it on his/her developer site. Make sure the developer website is the same as the one mentioned on the App Store and Play Store.

How does app-ads.txt Benefit Publishers?

Prevent ad fraud: Fraudsters often clone the original applications and lead advertisers to spend their budget on illegitimate inventory. As a result, publishers lose revenue that is rightfully theirs. In most cases, publishers aren’t able to calculate the losses caused by spoofing.

Promotes buyer trust: Even though app-ads.txt is not mandatory, some buyers may reject inventory without an authorized sellers file. DSPs also don’t want their spend to go to waste. Hence, for publishers, app-ads.txt can help create more trust with buyers.

How Does IAB Plan to Maximise the Use of App-ads.txt?

Just like app.txt, the benefits of the app-ads.txt should self-evidently encourage adoption. 

The buyers don’t want their investment to go to waste. Hence, app-ads.txt is likely to see an adoption push from the demand-side as well. While constantly updating app-ads.txt can be a tedious affair, it’s worth the effort considering the benefits of implementing it.


Shubham is a digital marketer with rich experience working in the advertisement technology industry. He has vast experience in the programmatic industry, driving business strategy and scaling functions including but not limited to growth and marketing, Operations, process optimization, and Sales.

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