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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 inventory.

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:

  • The ability to create and post a .txt file to your domain’s server. This means ads.txt is only available for:
    • Desktop and mobile web
    • Video players
  • Access to the domain name and seller account ID, or IDs, for each advertising system you wish to authenticate.

Ads.txt Fields

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

FieldIAB field nameDescription and exampleRequired?
Field 1Domain Name of the Advertising SystemThe domain name of the system to which bidders connect.

Field 2Seller Account IDThe publisher account ID in OpenX.

Note: OpenX provides you with OpenX-specific line(s) for your ads.txt file. If you have not received them, contact OpenX.

Example: 123456789
Field 3TYPE OF ACCOUNT/RELATIONSHIPThe 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.

Note: 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 4Certification Authority IDAn 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.

Note: 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.

Example: 6a698e2ec38604c6
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 an account 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 an account ID of 987654321.

Setting Up ads.txt

To set up ads.txt:

  1. If you have not received the OpenX-specific line(s) for your ads.txt file, 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.


    You can find your account Ads.txt in Administration > Accounts > Publisher Account > Details > Ads.txt.

  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.


Update your ads.txt file for each ad network who is authorized to sell or resell your inventory.