According to the Audience Network Policy
Publishers that maintain an ads.txt or app-ads.txt file must include Audience Network listed appropriately and accurately.
How can facebook crawl the app-ads.txt file from the domain?
If i don't add app-ads.txt file, is it violating policy?
How can facebook crawl the app-ads.txt file from the domain?
See the app-ads.txt specifications here: https://iabtechlab.com/wp-content/uploads/2019/03/app-ads.txt-v1.0-final-.pdf
which says:
Provide developer website URL in app store listings
This specification relies on the presence of a developer website URL within the app’s store listing metadata in all app stores distributing the app. Many app stores currently collect the developer's website URL to display as developer contact information within the store. Publishing a website and providing its URL is required for the app’s ad inventory to participate in the authorized seller scheme. Using this website URL, interested crawlers will derive a path and attempt to crawl an app- ads.txt file on the corresponding domain.
