An IAB Tech Lab standard that lets app publishers declare which ad networks are authorized to sell their inventory.

Where do I put the app-ads.txt file?

At the root of the developer website listed in your App Store / Google Play page, e.g. https://studio.com/app-ads.txt.

What is a Certification Authority ID?

An optional TAG-ID of the ad system, the 4th field of an app-ads.txt record.

chessfriends.com achieves the best ad optimization: its app-ads.txt has no errors and matches what its ad network expects (100% of 1 line).

Checked 21 Oct 2026. 2 lines, 2 unique records, 0 duplicates, 0 invalid lines, 1 ad network detected.

Google AdMob — accounts pub-5240105857279678, pub-3940256099942544: 2 lines in the file

Yes — https://chessfriends.com/app-ads.txt has 2 lines (checked 21 Oct 2026).

Its app-ads.txt lists Google AdMob.

chessfriends.com achieves the best ad optimization: its app-ads.txt has no errors and matches what its ad network expects (100% of 1 line).