ads.txt Checker & Validator
Validate your ads.txt file for syntax errors, duplicate entries, missing authorized sellers, and unauthorized resellers. Our checker follows the IAB Tech Lab specification and cross-references your file against detected demand partners on your site.
ads.txt validation is included in every RevenueRx audit. No signup required.
What our ads.txt checker validates
Six automated checks based on the IAB Tech Lab ads.txt specification.
File exists and is accessible
Verifies your ads.txt file is reachable at your domain root with an HTTP 200 response. Follows redirects up to 3 hops.
Syntax validation
Parses every line per IAB specification: domain, publisher-id, relationship, certification-authority-id. Flags malformed entries.
Duplicate entry detection
Identifies duplicate entries (same domain + publisher ID + relationship) that bloat your file and mask issues.
Demand partner matching
Cross-references DIRECT entries against ad networks actually detected on your site. Flags gaps where active partners are missing.
Certification authority IDs
Checks coverage of TAG certification authority IDs. Higher coverage improves supply chain transparency and buyer trust.
Unauthorized reseller detection
Flags unrecognized seller domains by cross-referencing against 100+ known ad exchanges and SSPs. Helps identify unauthorized resellers.
Why ads.txt errors cost you money
43%
of publisher sites have ads.txt errors
15-30%
potential revenue lost from misconfigurations
100+
known SSP/exchange domains we validate against
When a buyer's DSP checks your ads.txt and can't find the seller, the bid is dropped. Syntax errors can cause entire files to be ignored. Missing entries for active partners mean their bids never reach you. Every error is a revenue leak.
Common ads.txt errors we find
Inline comments breaking relationship fields
Example: google.com, pub-1234, RESELLER #comment
Fix: Ensure comments after # are separated from the relationship field with proper parsing. Some DSPs read "RESELLER #comment" as an invalid relationship type.
Missing entries for active demand partners
Example: You have PubMatic bidding via Prebid.js but no pubmatic.com DIRECT entry
Fix: Cross-reference your header bidding partners with your ads.txt entries. Every SSP you work with directly needs a DIRECT entry.
Stale entries from discontinued partners
Example: Entries for ad networks that have been acquired, rebranded, or shut down
Fix: Review your ads.txt quarterly and remove entries for partners you no longer work with. Stale entries add noise and can mask real issues.
Frequently asked questions
What is an ads.txt file?
ads.txt (Authorized Digital Sellers) is a text file that publishers place at the root of their domain (e.g., example.com/ads.txt) to declare which companies are authorized to sell their ad inventory. It was created by the IAB Tech Lab to combat ad fraud and unauthorized inventory reselling.
Why do I need to validate my ads.txt file?
Syntax errors, missing entries, or unauthorized resellers in your ads.txt file can cause demand-side platforms (DSPs) to drop bids for your inventory, directly reducing your ad revenue. Regular validation ensures your file is clean and all your partners are properly declared.
How often should I check my ads.txt file?
Validate your ads.txt file whenever you add or remove a demand partner, and at minimum once per month. Changes in SSP domain names, ad tech company mergers, and accidental edits can introduce errors over time.
What's the difference between DIRECT and RESELLER?
DIRECT means your organization has a direct business relationship with the ad system (you control the account). RESELLER means another entity (like a reseller or intermediary) has the relationship, and you've authorized them to sell your inventory.
What errors does RevenueRx check for?
RevenueRx validates file accessibility, syntax per IAB specification, duplicate entries, DIRECT entries matching your detected demand partners, certification authority ID coverage, and flags unrecognized or unauthorized reseller domains against 100+ known exchanges.
Related resources
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