> app-ads.txt lists the companies authorized to sell an app's ad inventory. How the file works, where it lives, and what buyers check.

Source: https://appsupplyindex.com/learn/what-is-app-ads-txt · Updated: 2026-10-07 · License: CC BY 4.0 (App Supply Index)

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[Learn](https://appsupplyindex.com/learn/) · Basics

# What is app-ads.txt?

Updated Oct 7, 2026 · data from 12 App Store genres · top free + top grossing charts · US · iOS + Android

**Short answer:** app-ads.txt is a public text file in which an app developer lists the companies authorized to sell
the app's ad inventory. Buyers read it to check that an ad request for an app comes from an authorized seller. It's
the mobile version of ads.txt, defined by IAB Tech Lab.

## Where it lives

Buyers find it through the developer website in the app's store listing (App Store or Google Play): the file is
served at `https://<developer domain>/app-ads.txt`. One file covers every app that lists that
developer website.

## What a line looks like

```
pubmatic.com, 156xxx, RESELLER, 5d62403b186f2ace
```

1. **Ad system domain**: the exchange or SSP the account is on.
2. **Seller ID**: the account at that ad system.
3. **Relationship**: `DIRECT` if the publisher controls the account, `RESELLER` if another
   company does (see [DIRECT vs RESELLER](https://appsupplyindex.com/learn/direct-vs-reseller)).
4. **Certification authority ID** (optional): the ad system's ID with a certification body such as TAG.

Files can also declare variables such as `OWNERDOMAIN` and `MANAGERDOMAIN`
([explained here](https://appsupplyindex.com/learn/ownerdomain-managerdomain)) and `CONTACT`.

## How buyers use it

A buyer receives an ad request saying "app X, sold by account Y at exchange Z". It checks that the app's
app-ads.txt lists exchange Z with account Y. Then it can look up account Y in exchange Z's
[sellers.json](https://appsupplyindex.com/learn/sellers-json) to see who operates it.

## What we see in practice

Across 883 ad-monetized top US apps in this index, 16.0% of seller lines
point to accounts that the ad system's own sellers.json doesn't list, and in the typical app
21% of DIRECT lines are [inconsistent with
public data](https://appsupplyindex.com/fix/inconsistent-direct). Large files often grow by pasting partners' blocks without removing old ones.

## Related

- [app-ads.txt not found: how to fix it](https://appsupplyindex.com/fix/app-ads-txt-not-found)
- [What is sellers.json?](https://appsupplyindex.com/learn/sellers-json)
- [How the index checks files](https://appsupplyindex.com/methodology)

Based on the [IAB Tech Lab
ads.txt/app-ads.txt](https://iabtechlab.com/ads-txt/) and [sellers.json](https://iabtechlab.com/sellers-json/)
specifications. Numbers are automated observations of public files on the date above.