Manage ads.txt for subdomains

Understanding ads.txt for subdomains

When a subdomain has a different ads.txt file from the root (top-level) domain, specific steps must be followed to ensure proper ad authorization:

Step-by-step process

1. Identify the different ads.txt File:
   • Determine if the subdomain has a different ads.txt file than the root domain.
2. Adding a line in the root domain’s ads.txt:
   • In the root domain’s ads.txt file, add a line indicating the subdomain’s presence.
   • For example, if your subdomain is sub.example.com and the root domain is example.com, the line in example.com/ads.txt should read: subdomain=sub.example.com.
3. Handling multiple subdomains:
   • Repeat this process for each subdomain with a different ads.txt file.
   • Example: subdomain=news.example.com in example.com/ads.txt.

Importance of accurate ads.txt

• Without this indication, DSPs (Demand-Side Platforms) and SSPs (Supply-Side Platforms) may not recognize the ads.txt of the subdomain, leading to authorization issues and potentially impacting ad delivery.

Additional resources

• For more detailed guidance, refer to the IAB ads.txt implementation guide, particularly pages 12 & 14 - IAB OpenRTB Ads.txt Public Spec (reference screenshots below)