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.

buienradar.nl achieves the best ad optimization: its app-ads.txt has no errors and matches what its 7 ad networks expect (100% of 20 lines).

Checked 19 Oct 2026. 88 lines, 70 unique records, 8 duplicates, 0 invalid lines, 7 ad networks detected.

Google AdMob — accounts pub-8076754774830443, pub-2678732374147763, pub-5443109342713637 and 1 more: 4 lines in the file
Xandr (Microsoft) — accounts 7463, 9302, 9994: 3 lines in the file
Criteo — accounts B-060835, B-059589: 2 lines in the file
Index Exchange — accounts 184476, 188249, 189915: 3 lines in the file
OpenX — accounts 540995958, 540995960: 2 lines in the file
PubMatic — accounts 156353, 156946, 158056 and 2 more: 5 lines in the file
Magnite (Rubicon) — accounts 12108, 21576, 20118 and 1 more: 4 lines in the file

Yes — https://buienradar.nl/app-ads.txt has 88 lines (checked 19 Oct 2026).

Its app-ads.txt lists Google AdMob, Xandr (Microsoft), Criteo, Index Exchange, OpenX, PubMatic, Magnite (Rubicon).

buienradar.nl achieves the best ad optimization: its app-ads.txt has no errors and matches what its 7 ad networks expect (100% of 20 lines).