What Is ads.txt?

ads.txt (short for Authorized Digital Sellers) is a standard introduced by the IAB Tech Lab in 2017, aimed at making the advertising ecosystem more transparent and preventing fraud. This standard is not just an innovation but a pillar of trust in the digital advertising market: it helps publishers authenticate their partners, and allows advertisers to buy reliable inventory. Ongoing developments ensure that ads.txt accurately reflects business relationships—making them transparent.

What Does It Look Like in Practice?

ads.txt is a simple text file placed in the root directory of a publisher’s website. It lists the ad sellers authorized to sell the advertising space of that site. This way, it becomes verifiable whether a representative is legitimately entitled to sell that inventory.

Why Is It Necessary?

A common fraud method in digital advertising is when someone illegally tries to sell ad space on a reputable platform. The purpose of ads.txt is to filter out such fraudsters, ensuring that only entities approved by the website's management can represent the publisher in the ad marketplace.

What Do "ownersdomain" and "managerdomain" Mean?

These designations provide more context about the background of a given inventory.

• OWNERSDOMAIN – Indicates which organization owns the website or app. This is especially important if a media group operates multiple websites or represents various brands.   
• MANAGERDOMAIN – Signals that the domain’s ad management is handled by an external company, not by the domain itself.   

This distinction is important because the digital advertising market is a complex, multi-actor ecosystem. It’s common for the company that owns the website to outsource ad sales. However, for advertisers, it is crucial to know the supply chain through which the inventory can be accessed safely.

The Role of sellers.json and the SupplyChain Object

To get a full picture of who is selling digital ad inventory and how, ads.txt alone is not sufficient. This is why the sellers.json and SupplyChain object standards were introduced.

sellers.json is a public list published by SSPs (Supply-Side Platforms) and ad exchanges that identifies who is selling ad inventory through them. Advertisers can use it to verify whether a given partner is a registered entity. The SupplyChain object is a real-time data structure that traces the path of an ad impression and shows who was involved in its sale. Together, ads.txt, sellers.json, and the SupplyChain object create a transparent, traceable, and verifiable advertising infrastructure.