ads.txt vs app-ads.txt: what's the difference?
For websites you use ads.txt; for mobile apps you use app-ads.txt in a different place.
ads.txt is for websites and must be hosted at your website root (/ads.txt).
app-ads.txt is for mobile apps and is hosted on the developer's website domain (also at /app-ads.txt).
Both files help ad systems verify who is authorized to sell inventory.
If you only run a website, focus on ads.txt.
If you also have an app, your ad partner will guide you to app-ads.txt requirements.