Last updated on July 11, 2018

Proposed by the Interactive Advertising Bureau (IAB), ads.txt, or Authorized Digital Sellers, is an initiative which aims to improve transparency for the world of programmatic advertising by enabling content owners to specify which advertising systems and resellers are authorized to sell their inventoryAd space available on a website or app. The basic unit of inventory for OpenX is an ad unit..

Adoption of ads.txt can help prevent domain spoofing and the sale of unauthorized inventory by providing a simple way for demand-side platforms (DSPs) to check if inventory from a particular source has been authorized for sale by the domain owner.

You can learn more by reading the following IAB topics:


  • Increased transparency.

  • Accurate representation of inventory.

  • Removes counterfeit inventory from the ecosystem, preserving CPMs and inventory scarcity.

  • Decreased revenue for fraudsters.


In order to take advantage of ads.txt, you must have the following:

Ads.txt fields

If you have not received the OpenX-specific line(s) for your ads.txt file, please contact OpenX. For your reference, each OpenX-specific line in the ads.txt file should include:


IAB Field Name




Field 1

Domain Name of the Advertising System

The domain name of the system to which bidders connect.


Field 2

Seller Account ID

The publisherAn account type that represents a business with ad space to sell. account ID in OpenX. In the OpenX UI, this is called the Legacy ID.

Important: Various account objects have Legacy IDs. Therefore, OpenX provides you with OpenX-specific line(s) for your ads.txt file. If you have not received them, please contact OpenX.



Field 3


The type of account, either:

  • DIRECT: The publisher directly controls the account in Field 2 on the system in Field 1.
  • RESELLER: The publisher has authorized another entity to control the account indicated in Field 2 and resell their ad space via the system in Field 1.
  • Tip: The IAB specifies that DSPs should treat this field as case insensitive when interpreting data. For simplicity and uniformity, OpenX recommends that the value in this field be typed in all capital letters.



Field 4

Certification Authority ID

An ID that uniquely identifies the system in Field 1 within a certification authority. OpenX has been thoroughly vetted and certified by the Trustworthy Accountability Group (TAG). The TAG ID for all OpenX lines in the ads.txt file is 6a698e2ec38604c6.

Tip: While this field is optional, OpenX highly recommends inserting the TAG ID in the OpenX lines of your ads.txt file. This field may become required in the future. Utilizing it now saves you from needing to revise it at a later time.


Optional, but highly recommended

Ads.txt format

Each line is formatted as follows:

 Domain Name of the Advertising System, OpenX Account ID, TYPE OF ACCOUNT/RELATIONSHIP, (Optional) Certification Authority ID

In this live example, the publisher has two OpenX accounts:

  • The first line of the example illustrates that the publisher is using OpenX directly, with a Legacy ID of 123456789.

  • The second line of the example shows the publisher authorized another entity as a reseller of the ad space. That entity has a Legacy ID of 987654321.

Setting up ads.txt

  1. If you have not received the OpenX-specific line(s) for your ads.txt file, please contact OpenX. Each line contains the fields described in the Ads.txt fields section.

  2. If you don't already have one, create a .txt file and name it ads.txt.

  3. Paste the information provided by OpenX into your ads.txt file.

  4. Post the ads.txt file to the root directory of your domain's server for the appropriate website.

    The file can be accessible via HTTP or HTTPS but must be located under a standard relative path: "ads.txt". The HTTP request header must contain "Content-Type: text/plain".

Tip: Update your ads.txt file for each ad networkAn OpenX account type, which represents a business that manages other businesses and typically contains and manages both publisher accounts and advertiser accounts. who is authorized to sell or resell your inventory.

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