Ads.txt FAQ

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Ads.txt Frequently Asked Questions and Best Practices

Living document August 2017 Guidance

Note to the reader: This information is compiled based on the Ads.txt specification version 1, and the current common best practices in place in the industry. The intention of this document is to provide additional clarity or examples of implementation strategies. The following information has not yet been standardized and should be evaluated by each implementing party before adhering to these best practices. For readers who would like to participate in the development of the standards for ads.txt - IAB Tech Lab members are invited to join the OpenRTB working group to collaborate on future directions.


Is ads.txt US only? This anti-fraud solution is globally available and globally impactful.

Real time processing

Is ads.txt used in real time bidding? Expectation is that buyers, ad tech vendors, or third parties will aggregate ads.txt files. The expected frequency is to crawl the web two to three times a week (minimum every 7 days), and aggregate in a non real time cadence. These aggregate files can be compared to actual RTB media spend, and buyers will reconcile the inventory purchased against the record of authorized digital sellers. This can inform targeting strategies for real time bidding.

Security and Anti-Fraud

Can ads.txt be spoofed? A beautiful feature of ads.txt is that if a fraudster attempts to spoof the ads.txt file by copying the file to a fake website, the seller account IDs still represent the legitimate business account, so the money is still directed to the legitimate business (and the media spend does not go to the fraudster). If the publisher’s website is hacked and ads.txt file is compromised, this is a problem outside of the scope of ads.txt efforts.

Mobile in-app inventory

Does ads.txt work for mobile in-app inventory? This is a known needed future direction for the ads.txt standard. Please join the OpenRTB working group to help solve this area. In the meantime, some in-app publishers who represent their inventory with a domain are able to host an ads.txt file on the web domain associated with their app.

Media spend and brand strategy

How can buyers take action? Crawl, aggregate, and shift media budgets. Already some DSPs and buyers are shifting their strategies to authorized digital seller inventory only. ….

Blanket Inclusion of Resellers

As a publisher, how many advertising systems should I list in my ads.txt file? Which vendors should be included in the ads.txt file? Publishers should only include advertising systems in their ads.txt file of whom there is a known and authorized partnership established for selling or reselling. Publishers should not include unknown, untrusted, or any vendor that they do not have a business relationship with in the ads.txt file that represents the publisher inventory. The intention of the ads.txt file is to list advertising systems where payment to the publisher is expected.


As a buyer, can I aggregate the ads.txt files from all the publisher inventory that I buy? As a publisher, how can I help buyers understand comments I include on my ads.txt files? Ads.txt is specifically designed to allow publishers and other sellers to communicate to buyers of various forms the list of parties allowed to resell their inventory.

There’s ambiguity as to whether third parties can aggregate the published ads.txt content and offer the aggregation to buyers.

It is proposed that the aggregation of ads.txt files be considered, by default, permitted use. In order to support this, an additional field is recommended to contain an opt-out of aggregation. Options:

  • On the first line, as a comment, the ads.txt file may include: “#no-aggregate”.
  • On the last line, as a comment, the ads.txt file may include: “#no-aggregate”.
  • The first line may be updated to be a “flags” line to declare things like no-aggregate and other global preferences.

Future Directions

What remains to be solved for ads.txt? Mobile, syndication, blind inventory, ...


Who has adopted ads.txt? List to come


What additional resources are available? Tech Lab Partner Interaction Guide Google (link) AppNexus (link) others?