ads.txt (Authorized Digital Sellers) is an IAB Tech Lab standard that lets publishers publicly list which companies are authorized to sell their ad inventory. It's a plain text file hosted at the root of your domain, and it's the backbone of the anti-fraud system that Google AdX, OpenX, Rubicon, and every major SSP uses to verify inventory authenticity.
Every demand partner crawls your ads.txt regularly. If they can't find themselves in your file, or if the file has syntax errors they can't parse, they stop bidding on your inventory. That's a silent revenue leak most publishers never catch.
Every non-comment line in ads.txt is a record with this structure:
DOMAIN, PUBLISHER_ACCOUNT_ID, DIRECT or RESELLER, CERTIFICATION_AUTHORITY_ID
Example records:
google.com, pub-1234567890123456, DIRECT, f08c47fec0942fa0 rubiconproject.com, 54321, RESELLER, 0bfd66d529a55807 openx.com, 540123456, DIRECT # Comments start with a hash
Fields:
google.com, not adsense.google.com).DIRECT if you have a direct contract; RESELLER if a reseller authorized you.DIRCT or Resler)Exactly at the root of your domain: https://yoursite.com/ads.txt. Not /ads.txt.html, not /public/ads.txt, not /wp-content/ads.txt. Crawlers only check the root URL. The file must be served with Content-Type: text/plain and return HTTP 200.
For subdomains (e.g. blog.yoursite.com), you have two options: host a separate ads.txt at each subdomain root, or use a SUBDOMAIN= redirect directive to delegate to your main domain's file.
Demand partners that can't parse your file (or can't find themselves in it) stop bidding on your inventory. You'll see lower CPMs, lower fill rates, and potentially disabled demand sources — all silently. No error message, just revenue loss.
Yes. AdSense specifically warns about ads.txt issues in its dashboard, and a missing or malformed ads.txt can reduce your AdSense revenue by 10-30%. Google's crawlers flag unauthorized inventory.
Every time you add or remove a demand partner. For publishers on header bidding platforms, this can be weekly. WeForAds auto-generates and updates your ads.txt whenever our partner list changes — no manual edits needed.
ads.txt is published by publishers (listing who can sell their inventory). sellers.json is published by ad systems (listing which publishers they represent). Together they form the "authorized seller chain" that buyers use to verify inventory authenticity. Both are IAB Tech Lab standards.
Yes. app-ads.txt is the mobile app equivalent of ads.txt. If you're a web publisher, you only need ads.txt. Apps use app-ads.txt hosted at their developer website.
Due to browser CORS restrictions, direct fetches from other domains may be blocked. If the URL mode doesn't work for your site, use the Paste Contents tab — simply view the file in your browser (visit yoursite.com/ads.txt), copy all the text, and paste it in.