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.

cna.com.tw achieves the best ad optimization: its app-ads.txt has no errors and matches what its 4 ad networks expect (100% of 4 lines).

Checked 21 Oct 2026. 12 lines, 9 unique records, 0 duplicates, 0 invalid lines, 4 ad networks detected.

PubMatic — account 159856: 1 line in the file
Magnite (Rubicon) — account 22884: 1 line in the file
Index Exchange — account 194511: 1 line in the file
Google AdMob — accounts pub-1937576406332709, pub-8371749267191729, pub-5446710434991921: 3 lines in the file

Yes — https://cna.com.tw/app-ads.txt has 12 lines (checked 21 Oct 2026).

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

cna.com.tw achieves the best ad optimization: its app-ads.txt has no errors and matches what its 4 ad networks expect (100% of 4 lines).