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.

baur.de achieves the best ad optimization: its app-ads.txt has no errors and matches what its 5 ad networks expect (100% of 7 lines).

Checked 19 Oct 2026. 558 lines, 479 unique records, 78 duplicates, 0 invalid lines, 5 ad networks detected.

PubMatic — accounts 156439, 154037: 2 lines in the file
Magnite (Rubicon) — account 16114: 1 line in the file
OpenX — accounts 537149888, 539401148: 2 lines in the file
Xandr (Microsoft) — account 3703: 1 line in the file
Google AdMob — accounts pub-1575911585432548, pub-2593767602602158, pub-1117059752672954 and 1 more: 4 lines in the file

Yes — https://baur.de/app-ads.txt has 558 lines (checked 19 Oct 2026).

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

baur.de achieves the best ad optimization: its app-ads.txt has no errors and matches what its 5 ad networks expect (100% of 7 lines).