AppNexus Support for Ads.txt and App-Ads.txt
The information in this document is based on the latest Ads.txt specification for the IAB as of January 22, 2018, and App-Ads.txt specification as of March 2019. 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 txt and app-ads.txt are some tools among a range of strategies we employ to ensure the quality of inventory and the validity of impressions.
Ads.txt and App-Ads.txt (also known as Authorized Digital Sellers) is or Application Authorized Digital Sellers) are 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 and app-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.
Ads.txt files are used to declare authorized sellers of display inventory on domains. app-ads.txt files are used to declare authorized sellers of application inventory.
For 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 and App-Ads.txt initiatives, and is working with publishers, resellers, buyers, and bidders on implementation.
Seller Impact: AppNexus DSP will begin has been enforcing adsAds.txt compliance starting since January 24, 2018 whenever ads.txt files are detected, and will begin enforcing app-ads.These
txt compliance in August of 2019.
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 additional questions regarding how ads.text txt adoption may impact AppNexus clients, please contact AppNexus Support.
In practice, ads.txt is and app-ads.txt files are the name of a file files 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, 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.
- Web Publishers place the ads.txt file on their domains at a URL following the
- format `
- App publishers place the app-ads.txt file, per IAB recommendations, on the root of the developer website URL associated with their application in the relevant app store where the application is hosted.
Within the ads.txt / app-ads.txt file is a list showing each approved partner, along with each partner's tech platform (AppNexus, Google, Rubicon, etc.), account ID, and relationship to the publisher. 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 / app-ads.txt files must have the following format:
For example, let’s say a publisher worked with four AppNexus accounts. The ads.txt /app-ads.txt file on their domain would look like this:
The member-IDs shown in the example file above must be replaced by actual member IDs.
Certification ID (optional)
appnexus.com, 958, DIRECT, f5ab79cb980f11d1
Ads.txt / App-Ads.txt for AppNexus Sellers
Here are some simple steps sellers can take to start using Ads.txt and App-Ads.txt.
Anywhere in this document you see a reference to the member ID, AppNexus is referencing your AppNexus member ID, not your publisher ID. The ads.txt team at IAB has approved the use of the AppNexus member ID in publishers' ads.txt / app-ads.txt files, similar to how Google is planning to use network ID.
Publishers on the AppNexus platform should follow these steps to create and implement ads.txt files that contains their AppNexus seller information.
- Start by gathering up the list of all partners - ad networks, exchanges, and SSPs - where publisher inventory is sold.
- For each partner, collect the ad serving domain (appnexus.com), the AppNexus member ID, and your relationship with the member (DIRECT or RESELLER).
- Use any text editor to create a plain text file.
For publisher direct seats, add a line to the file that looks like this:
appnexus.com, <publisher member ID>, DIRECT
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:
Be sure to note that you need your member ID, not your publisher ID. For further questions, please reach out to AppNexus Client Support.
For publishers working with partners who have AppNexus seats, create lines that look like this, with one partner per line:
appnexus.com, <partner member ID>, RESELLER
Partners should be able to provide their member IDs.
- Save the file with the name ads.txt , and or app-ads.txt - depending on the type of inventory you are declaring the file for - and upload it to the root folder for the publisher domain, such as or app developer url declared in the relevant app store. (ie./ example.com/ads.txt or appdeveloper.com/app-ads.txt)
- Validate your ads.txt file using the AppNexus Ads.txt Validator. This tool will help you / app-ads.txt file using one of many free online resources for this purpose. This will help ensure that your ads.txt / app-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
Resellers working with publishers should make sure publishers include them in their ads.txt / app-ads.txt files to show that the reseller has permission to sell their inventory. This can be done by sending publishers the instructions in the "Publishers" section above (or simply directing them to this page) and a request to be added to their ads.txt files.
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 / App-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 / App-Ads.txt information to strengthen our existing inventory quality programs. Buyers working with sellers who have not yet implemented ads.txt / app-ads.txt should please direct them to this wiki page to get started.
For external bidders and DSPs planning to crawl publisher domains to gather seller information from ads.txt / app-ads.txt files, there are two key pieces of information required in order to correctly map inventory from AppNexus sellers: domain and member ID. AppNexus sellers will have a domain of appnexus.com. 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
- AppNexus Ads.txt Validator
- An AppNexus Update on Ads.txt Implementation - The AppNexus Impressionist
- WTF is Ads.txt? - Digiday Article
- IAB 1.01 Spec Ads.txt / App-Ads.txt Spec - IAB Techlab