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.

issuu.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 20 Oct 2026. 5 lines, 2 unique records, 0 duplicates, 0 invalid lines, 1 ad network detected.

Google AdMob — accounts pub-5290441401882090, pub-9685734445476814: 2 lines in the file

Yes — https://issuu.com/app-ads.txt has 5 lines (checked 20 Oct 2026).

Its app-ads.txt lists Google AdMob.

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