Understanding Sellers.json and Ads.txt: A Comprehensive Guide

The digital advertising landscape requires technologies and standards to enhance transparency and trust in the ecosystem. Among these, two critical initiatives stand out: Sellers.json and Ads.txt. Both are instrumental in combating ad fraud and fostering a clean, transparent supply chain, but they serve different purposes and operate in distinct ways. This blog post delves into the nuances of Sellers.json and Ads.txt, highlighting their similarities, differences, and how they collectively contribute to a safer digital advertising environment.

Introduction to Sellers.json

Sellers.json is a framework designed by the Interactive Advertising Bureau (IAB) Tech Lab that allows the buyers of digital advertisements to verify the entities selling digital inventory. Essentially, it’s a publicly accessible file hosted by ad exchanges, supply-side platforms (SSPs), and other programmatic advertising platforms, which contains information about the sellers and resellers of digital advertising. Each entry in a Sellers.json file provides details such as the seller’s name, ID, and the nature of their relationship to the inventory sold (i.e., direct or reseller).

Key Features of Sellers.jsonTransparency Identification Verification

  • Transparency: Enables buyers to see the final seller of a digital ad inventory.
  • Identification: Lists all parties involved in the sale and reselling of ad spaces.
  • Verification: Helps in verifying the authenticity of the digital inventory being purchased.

Pros and Cons of Sellers.json


  1. Enhanced Transparency: By disclosing the identities of sellers and resellers, Sellers.json increases the transparency of the ad supply chain.
  2. Fraud Prevention: It aids in identifying and blocking fraudulent entities and inventory from the advertising ecosystem.


  1. Complexity for Small Publishers: Smaller publishers may find it challenging to be accurately represented if they sell through multiple channels.
  2. Implementation Overhead: Requires ongoing maintenance and updates to ensure accuracy, which can be resource-intensive.

Introduction to Ads.txt

Ads.txt stands for Authorized Digital Sellers and is a simple, flexible, and secure method that publishers and distributors can use to publicly declare the companies they authorize to sell their digital inventory. By creating an Ads.txt file on their web servers, publishers can list the ad exchanges, SSPs, and other parties authorized to sell their inventory, thereby preventing unauthorized sales and domain spoofing.

Key Features of Ads.txt

  • Simplicity: Easy to implement and maintain with a simple text file.
  • Control: Gives publishers control over who is allowed to sell their inventory.
  • Prevention of Ad Fraud: Reduces the risk of counterfeit inventory by ensuring that only authorized sellers can transact.

Pros and Cons of Ads.txt


  1. Increased Control for Publishers: Publishers can easily manage and update their list of authorized sellers.
  2. Reduction in Domain Spoofing: Helps in curtailing the sale of counterfeit ad inventory.


  1. Dependence on Adoption: Its effectiveness hinges on widespread adoption by publishers and advertisers.
  2. Potential for Errors: Incorrect entries in Ads.txt files can inadvertently block legitimate sales channels.

Differences and Similarities


  • Focus: Ads.txt focuses on providing publishers with a mechanism to list authorized sellers, whereas Sellers.json offers transparency about the sellers and resellers in the programmatic ecosystem from the perspective of the ad exchanges and platforms.
  • Implementation: Publishers implement Ads.txt by hosting a file on their domain, whereas ad exchanges and SSPs implement Sellers.json by maintaining a comprehensive list of sellers.


  • Both aim to enhance transparency and trust in the digital advertising supply chain.
  • They combat ad fraud by providing mechanisms to verify and authenticate sellers.
  • Adoption of both standards is voluntary but highly encouraged for ensuring a clean ad ecosystem.


In the fight against ad fraud and to ensure transparency in the digital advertising supply chain, Sellers.json and Ads.txt play pivotal roles, albeit from different angles. Sellers.json provides a bird’s-eye view of the selling parties in the programmatic landscape, while Ads.txt empowers publishers to declare who can sell their inventory legitimately. Together, they form a robust defense mechanism against the prevalent challenges of ad fraud, domain spoofing, and unauthorized inventory sales, making the digital advertising environment safer and more transparent for all stakeholders.

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