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The information in this document is based on the latest Ads.txt specification for the IAB as of October 24January 22, 20172018. This This information is subject to change based on IAB updates to the specification.

In the online advertising ecosystem, many buyers are concerned that fraudulent impressions will negatively impact their advertising, resulting in campaign unreliability and lost revenue. AppNexus takes these concerns very seriously, and ads.text is one tool among a range of strategies we employ to ensure the quality of inventory and the validity of impressions. 

Ads.txt is an initiative (also known as Authorized Digital Sellers)  is an initiative 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 of ads.txt is to give publishers more control over who sells their inventory and help prevent counterfeiting, while giving buyers confidence that they're purchasing approved inventory. 




additional details about the IAB's work on this initiative, 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.

titleAds.txt Adoption and Support

Seller Impact: AppNexus DSP will begin enforcing ads.txt compliance starting January 24, 2018 whenever ads.txt files are detected.

  • These checks are performed daily. If ads.txt files are present, AppNexus will disable buying from parties that are not directly identified through publishers' ads.txt files as authorized resellers.
  • Deals, Managed, and external Bidder demand will not be impacted by ads.txt enforcement. If ads.txt file is present (checked daily), we disable buying from parties that are not directly identified through the publisher’s ads.txt files as authorized resellers.

Buyer impact: AppNexus SSP is encouraging all sellers to ensure they are listed in the ads.txt files of the inventory they are selling on AppNexus.

  • For more information about this process, see the IAB's How To Ads.txt.
  • There is no buyer opt-in process as this is default buying behavior.

For additional questions regarding how ads.text adoption may impact AppNexus clients, please contact AppNexus Support.

titleOn This Page

Table of Contents

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 a file that 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 Publishers place 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 on their domains at a URL following the format Within the ads.txt file is a list showing each approved partner, along with each partner's tech platform (AppNexus, Google, Rubicon, etc.), account ID, and the publisher’s relationship with to the accountpublisher. The The file gives publishers a way to list all of their approved SSP, ad network, and exchange partners (both direct and resellers). DSPs can then choose to leverage the information in the ads.txt file in order to ensure authorized resale compliance. 

All ads.txt files must have the following format:


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

Code Block, 958123, DIRECT, 882456, RESELLER

The first line of this example specifies that the publisher is using AppNexus ( directly with a member ID of 958123. The second line specifies that the domain can also be resold through a reselling partner with AppNexus member ID 882456. 


The member-ids 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 on structuring files and other processes relating to ads.txt. 

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 a fourth, optional field known as a a certification authority identifier that sellers may choose to include in ads.txt files. Sellers add this unique ID as an additional measure to demonstrate validity and trustworthiness of the advertising systemplatform being used. AppNexus has an identifier issued by the Trustworthy Accountability Group (TAG).


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


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


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

  1. Start by gathering up the list of all partners - ad networks, exchanges, and SSPs - where you sell your publisher inventory is sold.
  2. For each partner, you need collect 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 seatseats, add a line to the file that looks like this:

    Code Block, <member-id><publisher member ID>, DIRECT

    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:

    Image Removed

    You can also check with your AppNexus representative. Image Added

    Be sure to note that you need your member ID, not your publisher ID.

    If you work with any

    For further questions, please reach out to AppNexus Client Support.

  5. For publishers working with partners who have AppNexus seats, create lines that look like this, with one partner per line:

    Code Block, <member-id><partner member ID>, RESELLER

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

  6. Save the file with the name ads.txt, and upload it to the root folder of your for the publisher 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 correctly. 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 Resellers working with publishers , you'll need to should make sure the publishers include you them in their ads.txt file to ensure you have files to show that the reseller has permission to sell their inventory. Send the publisher the This can be done by sending publishers the instructions in the "Publishers" section above (or simply direct directing them to this page) along with your member ID so they can add you to and a request to be added to their ads.txt filefiles. 


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


To be correctly listed, resellers must work with publishers to ensure that their reseller member ID is included in the ads.txt file.

Ads.txt for Buyers

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


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 Buyers working with sellers who have not yet implemented ads.txt , should please direct them to this page to get started.


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 required 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.

Additional Client Tools and Resources

Related Topics