Ads.txt Validation Test
The ads.txt Validator fetches /ads.txt at the root of any domain and validates that publishers have properly declared the ad-tech vendors authorised to sell their inventory programmatically. ads.txt (and its mobile equivalent app-ads.txt) is the IAB standard that lets advertisers and DSPs verify they are buying real publisher inventory rather than spoofed traffic resold through unauthorised intermediaries. Missing or incorrect ads.txt costs publishers measurable ad revenue.
What This Tool Checks
- /ads.txt exists at the root of the domain
- app-ads.txt for mobile apps
- Syntactically valid lines (domain, account ID, relationship, cert)
- DIRECT vs RESELLER relationship designation
- Duplicate or conflicting entries
- Outdated entries for relationships no longer active
Why It Matters for SEO
Programmatic ad buyers increasingly require ads.txt to verify the publisher legitimately owns the inventory. Without it, your impressions may be filtered out by major DSPs, costing real CPM. The file is text, takes minutes to set up, and is updated whenever you add or remove an ad partner. There is no SEO downside; the only cost of a missing ads.txt is lost ad revenue.
How to Fix It
Publish an ads.txt file at the root of your domain listing every advertising partner you use. Keep it up to date — remove partners you no longer use, add new ones promptly. For mobile apps, also publish app-ads.txt at the developer's domain referenced in the app store listing.
How It Works
We fetch /ads.txt and /app-ads.txt at the root of the domain, parse each line against the IAB specification, and flag syntax errors, duplicates and outdated entries. Each authorised seller is reported with the relationship type (DIRECT or RESELLER).
Common Mistakes to Avoid
- No ads.txt at all (DSPs filter you out)
- Outdated entries for partners you no longer use
- Syntax errors that invalidate the file entirely
- Missing app-ads.txt for mobile app inventory
- Treating ads.txt as one-time setup instead of maintaining it
Quick Checklist
- /ads.txt exists and returns 200
- Every active ad partner listed
- No outdated or unused entries
- app-ads.txt published if you have mobile apps
- Reviewed quarterly