Standards

Ads.txt — Definition & Explanation

Authorized Digital Sellers — an IAB Tech Lab standard that publishers implement as a text file on their domain (yourdomain.com/ads.txt) declaring which companies are authorized to sell their ad inventory. Helps prevent domain spoofing and unauthorized reselling.

How Ads.txt Works

Publishers place an ads.txt file at their root domain listing each authorized seller with their exchange domain, publisher ID, relationship type (DIRECT or RESELLER), and optional certification authority. Buyers and exchanges crawl ads.txt files to verify seller legitimacy.

Why Ads.txt Matters for Publishers

Implementing a complete, accurate ads.txt file is required to access premium demand. Missing or incomplete ads.txt can result in CPM discounts of 20-40% as buyers avoid unverified supply.

Frequently Asked Questions

How do I update my ads.txt for Stellor Media?

Stellor Media provides specific ads.txt lines to add when you onboard. Stellor's team validates your ads.txt as part of the setup process.

What happens if ads.txt is missing?

Most premium DSPs filter out domains without ads.txt, significantly reducing demand and CPMs.

How often should ads.txt be updated?

Review and update ads.txt whenever you add or remove demand partners — typically every 3-6 months or when your SSP partners change.

Related Terms

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