What Is ads.txt? How Does It Work?

ads.txt (Authorized Digital Sellers) is an Interactive Advertising Bureau initiative that uses a file (in the root directory of the domain) to list all the companies authorized to sell online advertising on that website. This is designed to allow online shoppers to check the validity of online advertising sellers to prevent Internet fraud.

Google AdSense Support | What Is ads.txt? How does it work?
Google AdSense Support | What Is ads.txt? How does it work?

Which is the objective?

The mission of the ads.txt project is simple: Increase transparency in the programmatic advertising ecosystem. It is a simple, flexible and secure method that publishers and distributors can use to publicly declare the companies they authorize to sell their digital inventory.

When a brand advertiser buys media programmatically, it is based on the fact that the URLs have been legitimately sold by those publishers. The problem is that until now there was no way for a buyer to confirm who is responsible for selling those impressions. There are many different scenarios in which the past URL may not be an accurate representation of what the impression really is or who is selling it.

Where should I put the ads.txt file?

Similar to a robots.txt file, an ads.txt file is also hosted on the root domain of a website. Yet unlike the robots.txt file, the purpose of it is entirely different.

For example, the file would be accessible through domain.com/ads.txt

How does it work?

Currently, the file must include the following information as outlined by the IAB:

  • Domain name of the advertising system or ad exchange
  • Publisher account ID
  • Type of relationship (DIRECT, RESELLER)
  • Type of inventory (optional)

An example of a line in an ads.txt file would look like the following:

google.com, pub-123456789, DIRECT, f08c47fec0942fa0
aps.amazon.com, 37138964, DIRECT
aolcloud.net, 4687, RESELLER

More examples

A lot of major websites have started using it to protect themselves from online ad fraud. It is only a matter of time before every website that publishes ads will use it.

Adoption of ads.txt | What Is ads.txt? How does it work?
Adoption of ads.txt | What Is ads.txt? How does it work?

See also

IAB Tech Lab / Ads.txt Specification Version 1.0.1 (September 2017)

IAB Tech Lab / Ads.txt Specification Version 1.0.2 (March 2019)


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