The implementation of ads.txt works like the robots.txt. It is a text file hosted in the main directory of the domain that informs the ad tech and programmatic buyers about the vendors authorized to sell advertisement on that domain. Here the example of the ads.txt of ppc.land:
This month, Appnexus created the ads.txt validator, where webmasters can validate the ads.txt after implementation, or before implementation, just uploading the txt file:
Here the result:
With this validation tool, webmasters can be assured that the ads.txt is correctly implemented.