Supply chain
app-ads.txt
app-ads.txt is the version of ads.txt for mobile and CTV apps, a file on the app developer's website that lists which sellers are authorised to sell the app's ad inventory.
Apps do not have their own web domain, so the ads.txt trick needed an extension. With app-ads.txt, the developer hosts the file on the website listed for the app in its app store (Google Play, Apple App Store, Roku, Amazon and others). Buyers find that website through the store listing, fetch the file and check whether the seller in a bid request is authorised.
The IAB Tech Lab released app-ads.txt in 2019. It is especially important for in-app advertising and CTV, where app spoofing (faking a popular app's bundle ID) and SSAI spoofing have been widespread. The file format is the same as ads.txt: ad system, account ID, DIRECT or RESELLER, and an optional certification ID.
Limitations mirror ads.txt: it proves authorisation, not traffic quality. It also relies on the app store listing being accurate and on buyers correctly mapping bundle IDs across stores. Some CTV platforms and smaller stores have been slower to support it, leaving gaps fraudsters target.
Think of it like this
app-ads.txt is like a restaurant posting its list of approved delivery partners on its own website, because the food court it trades in has no noticeboard.
An example
A game on Google Play lists game-studio.example as its website; game-studio.example/app-ads.txt authorises three SSPs, so bids for the game's bundle via a fourth SSP are rejected.
Related terms
ads.txt
ads.txt (Authorized Digital Sellers) is a public text file on a website's domain listing which ad sellers and accounts are authorised to sell that website's ad inventory.
App spoofing
App spoofing is misrepresenting which mobile or CTV app an ad slot belongs to, typically by faking the app's bundle ID, so cheap or fake inventory is sold as a popular app.
In-app advertising
In-app advertising is ads shown inside mobile apps, such as games, utilities and social apps, as opposed to ads on websites viewed in a mobile browser.
sellers.json
sellers.json is a public file in which SSPs and exchanges list their seller accounts, naming who owns each one and whether it is a publisher or an intermediary.
CTV fraud
CTV fraud is ad fraud targeting connected TV and streaming inventory, such as spoofed apps, fake devices, SSAI spoofing and infected streaming boxes, exploiting CTV's high prices and harder verification.