ads.txt File Checker
Check and analyze your ads.txt file to verify authorized ad sellers. Detect errors, prevent ad fraud, and ensure proper programmatic advertising setup.
ads.txt is required by Google AdSense, Google Ad Manager, and major ad exchanges to prevent ad fraud.
ads.txt Status Guide
Common ads.txt Mistakes
- Missing or incorrect relationship type (must be DIRECT or RESELLER)
- Duplicate entries with same domain and publisher ID
- Malformed lines with fewer than 3 required fields
- File served with wrong Content-Type (HTML instead of text/plain)
Example ads.txt Entry
pubads.g.doubleclick.net, pub-1234567890123456, DIRECT, f08c47fec0942fa0
domain, publisher_id, relationship, cert_authority_id
ads.txt Location
Your ads.txt file must be accessible at:
https://yourdomain.com/ads.txt
Place the file in your website's root directory. Ensure it's served with Content-Type: text/plain header.
What this ads.txt Checker analyzes
This tool checks and analyzes your website's ads.txt file to verify authorized digital sellers and help prevent ad fraud.
- Detects ads.txt file availability and HTTP status
- Parses and validates DIRECT and RESELLER entries
- Identifies formatting issues and duplicate entries
- Counts authorized sellers by type (DIRECT/RESELLER)
- Provides recommendations for corrections
ads.txt helps prevent ad fraud by declaring which ad systems are authorized to sell your inventory.
Tip: Enter a domain (example.com) to check its ads.txt file.
What is ads.txt?
ads.txt (Authorized Digital Sellers) is a text file that website publishers place in their site root to declare which advertising systems are authorized to sell their digital inventory. It helps prevent ad fraud by ensuring only authorized sellers can monetize your content.
The ads.txt file should be located at https://yourdomain.com/ads.txt and must be served with the Content-Type: text/plain header. Ad platforms like Google AdSense, Google Ad Manager, and major programmatic ad exchanges require this file to verify authorized sellers before displaying ads.
Common issues with ads.txt files:
- Missing file (404 error) – ads.txt not found at the site root
- Served as HTML – server returns a webpage instead of plain text
- Malformed lines – entries don't follow the IAB format (domain, publisher_id, relationship, cert_authority_id)
- Duplicate entries – same seller listed multiple times
- Invalid relationship type – must be DIRECT or RESELLER
Without a properly formatted ads.txt file, ad platforms may reject your inventory or allow unauthorized sellers to monetize your site, leading to revenue loss and potential ad fraud.
Frequently Asked Questions
Where should I place my ads.txt file?
Place your ads.txt file in your website's root directory so it's accessible at https://yourdomain.com/ads.txt. For example, if your site is hosted at /var/www/html/, place the file at /var/www/html/ads.txt.
What is the correct format for ads.txt entries?
Each line in ads.txt follows this format: domain, publisher_id, relationship, cert_authority_id. The first three fields are required. domain is the ad system's domain, publisher_id is your account ID, relationship must be DIRECT or RESELLER, and cert_authority_id is optional.
What's the difference between DIRECT and RESELLER?
DIRECT means you have a direct relationship with the ad system and they sell your inventory directly. RESELLER means a third party (like an ad network or SSP) is authorized to resell your inventory. You should list both if applicable.
Why is my ads.txt file showing as HTML instead of plain text?
This usually happens when your CMS or server is routing /ads.txt requests to a page template instead of serving the actual file. Ensure your server configuration serves ads.txt as a static file with Content-Type: text/plain, or disable routing for this specific path.
How often should I update my ads.txt file?
Update your ads.txt file whenever you add or remove ad partners, change publisher IDs, or modify relationships. Ad platforms typically crawl ads.txt files periodically (daily to weekly), so changes may take a few days to be recognized. Keep the file up to date to avoid authorization issues.