ads.txt authorized sellers file

A file at /ads.txt naming the exchanges allowed to sell this site advertising. It only concerns sites that sell ads; on those it is what stops the domain being spoofed in a bid request.

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ads.txt ("Authorized Digital Sellers", an IAB Tech Lab specification) is a public list of the ad exchanges and resellers allowed to sell advertising space on your site. Buyers check it before bidding: an impression offered for your domain by a seller not on the list is treated as fraudulent. That is what stops someone else from selling fake inventory under your name and drawing down the price of the real thing.

It only matters for sites that sell programmatic advertising. A site without ads does not need one, and the report never marks its absence as a fault.

How SiteScan checks

The scan requests /ads.txt without following redirects and counts it as published only when the answer is a 200, not HTML, and contains at least one line in the defined format: exchange domain, publisher account ID, and DIRECT or RESELLER, separated by commas. A file with no valid line — or an HTML page served at that address — reads as not published.

How to publish one

Your ad network or exchange provides the exact lines; a typical entry looks like google.com, pub-0000000000000000, DIRECT, f08c47fec0942fa0. List every partner, keep the file in the root of the domain, serve it as text/plain, and update it whenever you add or drop a seller. Remember that ad scripts also affect speed and privacy — see third-party scripts.