The hype around IAB /ads.txt initiative is on. And even though its adoption might still lag, the biggest digital ad market players have already declared their support. Since the ads.txt are to become mandatory for publishers in the nearest future, it’s time to get a grip.

Here’s what you need to know about ads.txt and how to implement it.

What is /ads.txt?

Ads.txt refers to the “Authorized Digital Sellers” project by IAB and is basically a list of all parties (direct advertisers or ad networks), authorized to sell publisher’s ad inventory, compiled in a simple text file.

Posted to the root folder on a publisher’s website, the /add.txt file is available for referencing by programmatic buyers while purchasing ad inventory.

Why publishers need /ads.txt

The core benefit of adopting /ads.txt for publishers is clear.

Declaring Authorized Digital Sellers increases transparency, thus boosts buyers’ trust and confidence in the publisher’s ad inventory and its authenticity.

How to create and publish an /ads.txt file

First and foremost, a publisher needs to gather all information from their accounts from ad networks, resellers and other parties that work with their ad inventory.

Secondly, all gathered information should be added to a text file (e.g. using Notepad), according to the IAB guidelines, then saved under the filename “ads.txt”.

This information for each ad partner should adhere to the following format:

<FIELD #1>, <FIELD #2>, <FIELD #3>, <FIELD #4>

  • FIELD #1: Domain name
  • FIELD #2: Publisher’s account ID
  • FIELD #3: Account type (DIRECT/RESELLER)
  • FIELD #4 (Optional): Сertification Authority ID, if available.

The final step is to publish the saved ads.txt file to the root folder* of one’s website properties, so that the path to it will look like this: Please note that this URL string is just an example, thus visiting the URL will yield no result.

*Crawling /ads.txt files on subdomains isn’t supported yet.

Check out to a real-world example from Business Insider or read the full IAB specification for more implementation details.