> Plain-language guides to app-ads.txt, sellers.json, DIRECT vs RESELLER, and how to fix the issues the index finds.

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

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# Learn

Plain-language guides to the files behind mobile ad supply chains, with numbers from this index.

## Basics

- [What is app-ads.txt?](https://appsupplyindex.com/learn/what-is-app-ads-txt)
- [What is sellers.json?](https://appsupplyindex.com/learn/sellers-json)
- [DIRECT vs RESELLER](https://appsupplyindex.com/learn/direct-vs-reseller)
- [OWNERDOMAIN and MANAGERDOMAIN](https://appsupplyindex.com/learn/ownerdomain-managerdomain)

## How to fix issues

- [Why can't some app-ads.txt lines be verified against sellers.json?](https://appsupplyindex.com/fix/sellers-json-not-available)
  · 683 apps in the index
- [Why isn't my seller ID found in the ad system's sellers.json?](https://appsupplyindex.com/fix/seller-id-not-in-sellers-json)
  · 639 apps in the index
- [Why is my app-ads.txt DIRECT line flagged as inconsistent?](https://appsupplyindex.com/fix/inconsistent-direct)
  · 533 apps in the index
- [Why does the same line appear more than once in app-ads.txt?](https://appsupplyindex.com/fix/duplicate-app-ads-txt-lines)
  · 520 apps in the index
- [Should app-ads.txt include OWNERDOMAIN?](https://appsupplyindex.com/fix/missing-ownerdomain)
  · 466 apps in the index
- [What does it mean when an ad system domain in app-ads.txt doesn't resolve?](https://appsupplyindex.com/fix/ad-system-domain-does-not-resolve)
  · 434 apps in the index
- [Why is a DIRECT account registered to another company's domain?](https://appsupplyindex.com/fix/direct-account-other-domain)
  · 428 apps in the index
- [What is a confidential seller in sellers.json?](https://appsupplyindex.com/fix/confidential-seller)
  · 331 apps in the index
- [Malformed app-ads.txt lines: what crawlers ignore](https://appsupplyindex.com/fix/malformed-app-ads-txt-lines)
  · 291 apps in the index
- [app-ads.txt not found: how to fix it](https://appsupplyindex.com/fix/app-ads-txt-not-found)
  · 64 apps in the index
- [app-ads.txt exists but has no valid lines](https://appsupplyindex.com/fix/empty-app-ads-txt)
  · 9 apps in the index
- [Why does app-ads.txt need a developer website in the store listing?](https://appsupplyindex.com/fix/no-developer-website)
- [app-ads.txt can't be fetched by crawlers: common causes](https://appsupplyindex.com/fix/app-ads-txt-unreachable)
- [app-ads.txt with an invalid HTTPS certificate or HTTP only](https://appsupplyindex.com/fix/app-ads-txt-https-certificate)