app-ads.txt: A quick guide to authorizing mobile ad inventory

Overview

app-ads.txt is the mobile app counterpart to ads.txt, designed to prevent unauthorized ad selling by listing the ad networks that are authorized to serve ads for your app. It is part of a broader effort led by the IAB Tech Lab to bring transparency to programmatic advertising in mobile apps.

What is app-ads.txt

An app-ads.txt file is a plain text document hosted on your publisher domain that enumerates networks and publisher IDs permitted to sell or resell your app's ad space. The exact fields and syntax follow the IAB Tech Lab's app-ads.txt specification, which may include network domain, publisher/app identifiers, and optional attributes. Always refer to the official spec for the precise format.

Why it matters

Publishing app-ads.txt helps reduce ad fraud, protects your app's revenue, and improves transparency for advertisers and buyers. It makes it harder for bad actors to impersonate your app's inventory and directs buyers to legitimate sources.

How app-ads.txt works

Hosting and access

The app-ads.txt file is hosted at the root of your publisher domain, typically at a path like https://yourdomain.com/app-ads.txt. The file should be publicly accessible so advertisers, ad exchanges, and networks can verify the authorized sellers for your app.

Entry content and matching

Each line in the file represents an authorized ad network or marketplace and includes the identifiers needed to verify authorization. Fields and exact syntax are defined by the IAB Tech Lab's app-ads.txt specification. Some networks require an app identifier to tie the entry to a specific app. Keep entries up to date whenever you add or remove networks.

How to implement

Steps

1. Identify the domain you want to publish the file under and the app(s) you monetize.
2. Create app-ads.txt with the required entries for each authorized network, following the official spec.
3. Place the file at the root of the publisher domain (for example, https://yourdomain.com/app-ads.txt).
4. Ensure the file is publicly accessible and caching considerations are managed.
5. Update entries promptly if networks change and coordinate with your monetization partners.

Validation and testing

After publishing, verify that your file is reachable in a browser and that networks that should be listed are appearing in your partner dashboards. Some ad networks provide tooling to check app-ads.txt compliance.

Best practices

Maintenance

Treat app-ads.txt as a live document: update it whenever ad partners change, and keep a versioned record.

Monitoring

Periodically audit the file against your active networks and use partner dashboards to confirm that impressions are routed through authorized networks.

Common pitfalls

Common errors to avoid

• Not publishing the file at the root of your publisher domain.
• Listing wrong or outdated network identifiers.
• Forgetting to update the file after adding or removing networks.
• Relying on ads.txt alone for app inventory; align both web and app strategies.

Frequently asked questions

How is app-ads.txt different from ads.txt?

Ads.txt was designed for web inventory, while app-ads.txt extends the transparency concept to mobile apps, helping ensure only authorized networks serve your app’s ads.

Do I need to publish app-ads.txt for all apps on a domain?

If you monetize multiple apps under a single publisher domain, you generally publish entries that cover the relevant apps, as required by the spec and your networks. Check with your ad partners for exact requirements.