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AppNexus Support for Ads.txt

The information in this document is based on the latest Ads.txt specification for the IAB as of October 24, 2017. This information is subject to change based on IAB updates to the specification.

Ads.txt is an initiative (also known as Authorized Digital Sellers) put forth by the IAB Technology Laboratory as a way to help publishers ensure inventory is sold only through authorized dealers and partners. The goal is to give publishers more control over who sells their inventory and help prevent counterfeiting, while giving buyers confidence they're purchasing approved inventory. For more details, see About Ads.txt on the IAB website.

AppNexus supports the Ads.txt initiative and is working with publishers, resellers, buyers, and bidders on implementation.

On This Page


The Ads.txt File

So what exactly is Ads.txt? In practice, ads.txt is the name of a file that publishers can create and add to their websites. This file is a plain text file that lists names and information about authorized ad networks, SSPs, and exchanges that have permission to sell the publisher's inventory.

This idea is similar to robots.txt, which is used by website owners to give instructions about their site to web robots (such as search engine crawlers) about which parts of their website can be crawled and which should be off-limits.

Within the ads.txt file, the publisher will specify the domain of the advertising system used by your exchange, network, or SSP partner, along with the seller account ID, and the publisher’s relationship with the account.

The ads.txt file must have the following format:

For example, let’s say a publisher worked with two AppNexus accounts. The ads.txt file on their domain would read: 

The first line of this example specifies that the publisher is using AppNexus ( directly with a member ID of 958. The second line specifies that the domain can also be resold through a reselling partner with AppNexus member ID 882.

The member-ids shown in the example file above must be replaced by actual member IDs.

See How To Ads.txt on the IAB website for more information.

Certification ID (optional)

There is one optional field that you can add to each line of your ads.txt file: a certification authority identifier. You can add this unique ID as an additional measure to demonstrate validity and trustworthiness of the advertising system. AppNexus has an identifier issued by the Trustworthy Accountability Group (TAG).

To include the AppNexus TAG-ID, add the ID f5ab79cb980f11d1 to the end of each AppNexus line in your ads.txt file:

Ads.txt for AppNexus Sellers

Here are some simple steps you can take to start using Ads.txt.

Anywhere in this document you see a reference to the member ID, we're talking about your AppNexus member ID, not your publisher ID. The Ads.txt IAB team has approved the use of the AppNexus member ID in publishers' ads.txt files, similar to the way Google is planning to use network ID.


As a publisher on the AppNexus platform, follow these steps to create and implement an ads.txt file that contains your AppNexus seller information.

  1. Start by gathering up the list of all partners - ad networks, exchanges, and SSPs - where you sell your inventory.
  2. For each partner, you need the ad serving domain (, the AppNexus member ID, and your relationship with the member (DIRECT or RESELLER).
  3. Use any text editor to create a plain text file.
  4. For your publisher direct seat, add a line to the file that looks like this:

    Replace member-id with the member ID of your AppNexus account.

    Sellers can find their member ID in Console by navigating to the Monetization Dashboard and looking for the ID at the bottom of the screen:

    You can also check with your AppNexus representative. Be sure to note that you need your member ID, not your publisher ID.

  5. If you work with any partners who have AppNexus seats, create lines that look like this, one partner per line:

    Replace member-id with the AppNexus member ID of the partner you work with. Your partner should be able to provide you with this ID.

  6. Save the file with the name ads.txt, and upload it to the root folder of your domain, such as
  7. Validate your ads.txt file using the AppNexus Ads.txt Validator. This tool will help you ensure that your ads.txt file has been configured correclty. You can either enter the URL to your ads.txt file or upload your file, and the validator will will let you know if it identifies any issues. 

Publisher Reselling Partners

If you're a reseller working with publishers, you'll need to make sure the publishers include you in their ads.txt file to ensure you have permission to sell their inventory. Send the publisher the instructions in the "Publishers" section above (or simply direct them to this page) along with your member ID so they can add you to their ads.txt file.

If you have multiple member IDs, be sure to give all relevant IDs to the publisher and ask them to include each ID on a separate line of the ads.txt file.

Ads.txt for Buyers

The following sections describe how AppNexus works with Ads.txt for Console buyers and external bidders.

AppNexus Console Buyers

As a benefit to AppNexus Console buyers, AppNexus will begin to use Ads.txt information to strengthen our existing inventory quality programs. If you work with a seller who hasn’t implemented ads.txt, please direct them to this page to get started.

External Bidders

For external bidders and DSPs planning to crawl publisher domains to gather seller information from ads.txt files, there are two key pieces of information you need in order to correctly map inventory from AppNexus sellers: domain and member ID. AppNexus sellers will have a domain of The IDs of publishers, exchanges and SSPs will be sent in the seller_member_id field in the OpenRTB request.

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