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.

metservice.com achieves the best ad optimization: its app-ads.txt has no errors and matches what its 7 ad networks expect (100% of 12 lines).

Checked 19 Oct 2026. 49 lines, 17 unique records, 3 duplicates, 0 invalid lines, 7 ad networks detected.

Google AdMob — accounts pub-5527346396361189, pub-3779956271662848: 2 lines in the file
Magnite (Rubicon) — accounts 13178, 17658: 2 lines in the file
OpenX — account 541153842: 1 line in the file
Index Exchange — accounts 187268, 214631: 2 lines in the file
TripleLift — accounts 9136, 9136-EB: 2 lines in the file
PubMatic — accounts 157262, 156927, 167211: 3 lines in the file
Xandr (Microsoft) — account 17843: 1 line in the file

Yes — https://metservice.com/app-ads.txt has 49 lines (checked 19 Oct 2026).

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

metservice.com achieves the best ad optimization: its app-ads.txt has no errors and matches what its 7 ad networks expect (100% of 12 lines).