What is ads.txt?

Ads.txt is a Standard by the IAB and stands for "Authorized Digital Sellers". It is a simple text file which contains information about companies that are allowed to sell traffic from the website where the ads.txt is placed on (e.g. www.website.com/ads.txt tells which companies are allowed to sell traffic of www.website.com). With ads.txt a potential buyer can validate if the offered traffic is valid - or with other words: The buyer can verify if the seller is allowed to sell the traffic.

How does an ads.txt file look like?

The ads.txt file is very simple. Each line is one record. Each record consists of 3 to 4 fields separated by comma and an optional extension field separated by semikolon. Here is an example:


The four fields are:

  1. Domain name of the seller (SSP/Exchange)
  2. ID of the partner in the sellers system
  3. the word "DIRECT" or "RESELLER" depending on if its a direct connection between seller and website or if the seller is re-selling the traffic indirectly
  4. (optional) TAG ID

If a website works with 3 companies, the file contains 3 (or more) records. If the website works with more companies or has multiple accounts with some companies, the ads.txt file will obviously contain more rows.

An ads.txt file can also contain empty lines and comments. A comment is marked by a hastag (#): Everything that stands behind that # in the current line is a comment and will be ignored by parsers. Example:

#this is my ads.txt file
myssp.com,123,DIRECT,e72bc5a;extensionblabla #this is my ssp

How does it work with resellers?

Here is a bit more complex scenario:

In this case the website uses two SSP and these are (re-)selling to three exchanges. One of the exchanges also (re-)sells the traffic to a fourth exchange. At the end the traffic is offered to several DSP.
In this scenario it is not enough to include only the two SSP in the ads.txt because the DSP will get the traffic from exchanges (indirect). There the DSP will not be able to verify if the (exchanges) partner ID matches the ID in the ads.txt file. Hence it is necessary to include all parties in the ads.txt file:


In short: The website needs to ask both SSP if they are selling the traffic to a reseller. If that is the case, the website needs to add the reseller's info in its ads.txt file (in this case exchanges A, B and C). If one of the resellers sells the traffic to another reseller (exchange A to exchange D), then even this info needs to be included too.
At the end the ads.txt file needs to contain each party which is sending the traffic to a next party, so that the next party can verify it.

Hint: Use our managed ads.txt service in order to automate changes in your resellers ads.txt files!

Where do i get more info?

More info on ads.txt can be found on the pages of the IAB and the ads.txt spec itself:

What's ads.txt?

Ads.txt stands for "Authorized Digital Sellers". It is a mechanism on how a publisher/website owner can tell potential buyers that the traffic they are buying is valid. It also tells the buyer that the SSP/DSP from which they are receiving the traffic is wanted/allowed by the publisher. This prevents third parties ("ad-frauders") to send traffic to buyers and claim that the traffic originates from your website (by falsifying the referrer domain in the bid-request). Read more

What's ads.cert?

Ads.cert is a standard which is designed to sign and verify messages send via OpenRTB (RTB-Requests), allowing a seller to prove that the sold inventory is valid. A message is signed using private keys and can be verified using public keys. This way a buyer can ensure that the offered inventory is valid and adfraud can be reduced. Read more

What's app-ads.txt?

App-ads.txt is the ads.txt standard for mobile apps. It allows buyers to verify that a seller is really allowed to sell inventory for this certain app. It combines the logic from ads.txt with meta information from App stores.