What Is app-ads.txt?

Exploring how app-ads.txt enables mobile and CTV advertising

IAB’s ads.txt initiative has become an industry standard for digital advertising around the world, providing an effective and simple solution for combatting ad fraud and arbitrage. But what is app-ads.txt, how does it differ, and why is it important?


If you’re unfamiliar with app-ads.txt but have any stakes in advertising on mobile or CTV/OTT applications, this breakdown is for you.


For a deeper dive into baseline ads.txt for the uninitiated, take a look into our in-depth writeup.

Put more simply, ads.txt stands for Authorised Digital Sellers and was released in 2017. It comes in the form of a text file (.txt) that’s added by publishers to their websites to prove that they are who they say they are and counter arbitrage. You can find a site’s ads.txt file yourself just by adding /ads.txt to the end of their url – so it’ll look like example.com/ads.txt!


The simple system, developed in 2017 by the Interactive Advertising Bureau (IAB), packs a deceptively serious punch against would-be fraudsters. Domain spoofing fraud happens when unauthorized sellers claim to have ad space in their inventory that they don’t have rights to. Ads.txt is a verified, public handshake between publisher and exchange, meaning that buyers who only buy from ads.txt verified sellers will avoid fraudulent exchanges.


Ad arbitrage, the act of buying publisher inventory and then sneakily selling it for a markup, is also countered as ads.txt keeps track of authorized sellers for any given publisher.


Released in 2019, app-ads.txt is IAB’s extension of the widely popular ads.txt solution for publishers hosting ad space on applications.


Uploaded to a developer’s website, it works much the same way as regular ads.txt does – before buying ad inventory, DSPs will scan for an app’s authorized sellers via their developer site.


It helps combat the problem of app forging, where fraudsters will create copycat apps to siphon ad spend from legitimate app developers.


That’s not just relevant for mobile application developers, as it’s become a valuable practice for CTV app developers as well.


It took some time for app-ads.txt to find its footing in the CTV space due to something particular to CTV and, more widely, OTT apps: inventory sharing.


Inventory sharing happens when multiple entities simultaneously hold rights over an app’s ad space. It’s particular to CTV and OTT as there are multiple players involved in delivering content to consumers, such as Virtual Multichannel Video Programming Distributors, networks, and even the device manufacturers.


The added complexity posed a problem for widespread app-ads.txt adoption for CTV, as inventory sharing makes it exponentially harder to keep track of authorizations. That roadblock to adoption arguably contributed to the preventable high-profile CTV scams of 2020, such as ICEBUCKET, which impersonated over two million people, and StreamScam, which spoofed over 28.8 million US households.


As a response, IAB updated app-ads.txt to v1.0.3 in 2021, which adapts app-ads.txt for CTV and OTT inventory sharing with a streamlined and simplified verification process.


Widespread app-ads.txt adoption for CTV advertising helps protect one of the world’s most attention-grabbing mediums from fraud.


App-ads.txt will continue to evolve and improve thanks to IAB’s feedback-powered development.

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