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What Is An Ads.txt File?

What Is An Ads.Txt File

Date First Published: 9th April 2024

Topic: Web Design & Development

Subtopic: Web Advertising

Article Type: Computer Terms & Definitions

Difficulty: Medium

Difficulty Level: 7/10


Learn about what an advertising ID is in this article.

Stands for Authorised Digital Sellers. An ads.txt file is a text file hosted on the root directory of a website that publishers use to list all sellers they consider trustworthy and which are allowed to sell ad inventory on a specific domain name. This file protects publishers from unauthorised ad inventory sales. In addition, it allows advertisers to verify the publisher as only the owner of the website can edit the file, helping to prevent suspicious transactions.

How Does Ads.txt Work?

Ads.txt works as a publicly viewable list of authorised digital sellers that can purchase inventory from a publisher. Below are the steps of ads.txt.

  • To confirm ownership of the domain name and identify advertising partners, the publisher uploads the file to their website.
  • Advertisers crawl the web for publisher's ads.txt files and form a list of authorised sellers.
  • The advertiser checks their ads.txt file for their account ID when a publisher sends a bid request.
  • If everything matches, the advertiser knows the publisher is legitimate. However, if the advertiser fails to verify the publisher’s account, they may choose not to bid on that inventory.

Importance Of Ads.txt

Although ads.txt is not required, it is highly recommended. Below are three reasons why it is important to use one.

  • It prevents unauthorised sales - The file allows publishers to list the authorised ad networks and ad exchanges to give permission to sell their ad inventory. This prevents unauthorised sellers from making a profit by claiming access to the publisher's inventory.
  • It can prevent domain spoofing - Domain spoofing is when someone impersonates a publisher's domain name to sell fake inventory. By using this file, advertisers can protect against domain spoofing.
  • It can attract high-quality advertisers - By providing a transparent environment for advertisers, publishers can attract deals with high-quality, premium advertisers and receive higher earnings per click for their ad inventory. Without ads.txt, publishers could be at risk of losing out on earnings from top advertisers.


Ads.txt was introduced by the IAB Tech Lab in May 2017. It was designed to reduce ad fraud such as domain spoofing, or domain hijacking. It increases the transparency of the publisher’s ad inventory by allowing publishers to publicly list authorised sellers of their ad inventory and allowing ad buyers to validate the seller and avoid unauthorised sales.

The original publication of the IAB’s guidelines for the introduction of ads.txt did not support adequate steps to reduce mobile app fraud. As a result, app-ads.txt was developed to provide the same functionality that ads.txt was providing for web users.

In June 2018, the IAB Tech Lab posted an overhaul of the recommendations and made them open for users to give feedback on for a month. In August 2019, Google Ad Manager and AdMob implemented a feature which allowed clients with app-ads.txt to block unauthorised ad inventories.

The latest version of ads.txt is 1.1, which was released in August 2022. It includes two new values for publishers to declare within their ads.txt files, "OWNERDOMAIN" and "MANAGERDOMAIN".


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