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Sellers.json: Short Guide

These anti-fraud solutions are aimed to guarantee the safety and transparency of traffic resale allowing ad buyers to track which direct and intermediary sellers have been involved in every bid request.

Sellers.json: Short Guide
These anti-fraud solutions are aimed to guarantee the safety and transparency of traffic resale allowing ad buyers to track which direct and intermediary sellers have been involved in every bid request.
Nov 01, 2019
Kateryna Sorokina
Content Manager at Adtelligent Inc.

What is sellers.json?

Sellers.json together with SupplyChain object is the latest specification released by IAB Tech Lab in April 2019. It helps advertisers check on the stage of the bid request whether the certain reseller has permission for the publisher’s inventory distribution within the advertising chain.

Senior Vice President and General Manager in IAB Tech Lab Dennis Buchheim said, “Growth in the global digital advertising ecosystem requires trust, and Sellers.json and the SupplyChain object provide essential visibility into the supply chain, enabling buyers to curate media sources”.

How does sellers.json & Supply Chain Object work?

  • Sellers.json has similar functions as ads.txt. However, there is a JSON format is applicable instead of TXT (The JSON format is easier for humans to read and write). Sellers.json is placed in the root of the SSP domain and it is publicly available. The mechanism allows listing authorized ad tech vendors which are in partnership with a supply-side platform.
  • SupplyChain object is the second specification working along with sellers.json. This mechanism runs on the DSP side and helps buyers to watch so-called ‘nodes’ which determines every active reseller during the bid request. All vendors are automatically checked with parties IDs listed in ads.txt placed on the publisher’s side. Hence, the buyer/ advertiser may verify if vendors are in a partnership with the original seller.
  • Sellers.json and SupplyChain object are compatible with the open real-time bidding version 2.5 and 3.0. Ad tech vendors are responsible for hosting the files.

Sellers.json example

Let’s say a publisher works with a supply-side platform to sell their inventory. When the SSP sends an offer to the demand-side platform, ads.txt will display the following information:

  • Advertising system name
  • Sellers account ID
  • Domain

Sellers.json takes it a step further and gives DSP’s the following:

Sellers.json Example

This allows the platform to confirm the original publisher before initiating the bid request. You can take the domain of any platform which uses sellers.json and simply append “/sellers.json” to the end of it to access the file.

How is sellers.json implemented?

Advertising platforms post their sellers.json file on their root domain to make it easily accessible to you as we just described. They also make it crawlable via both HTTP and HTTPS protocols while the latter is preferred for security.

The parent object of the sellers.json file consists of five main properties:

  • Sellers
  • Identifiers
  • Email address for contacting the advertising system
  • The physical address of the advertising system
  • Spec version

How Is Sellers.json Implemented

The “sellers” attribute contains the identity of any parties that are paid to sell inventory while “identifiers” are common values to organize them.

Don’t worry if this seems a bit out of reach. This will all be taken care of when you work with a platform that implements sellers.json in their backend.

Who benefits from this solution?

It is a win-win initiative. Both publishers and advertisers receive benefits from the mechanism for verification of all intermediary sellers. The initiative gives advertisers and agencies confidence in what they buy and from whom exactly. Buyers having a high level of trust may likely to increase their spending on the advertisement. This is how it works schematically:

How Sellers.json Works Schematically

The brand safety issue is important for every player in the supply chain. Ad fraud remains a large and acute problem both for web and mobile advertising. According to Juniper Research, advertisers can lose 20% more ad spending because of fraudulent activities. Last year $35 billion lost to advertising fraud, and it’s expected $42 billion of ad expenses globally by the end of this year. So sellers.json and SupplyChain object working together with ads.txt and app-ads.txt clean up digital ad ecosystem blocking out fraudsters.

The other side of the coin is that the implementation of sellers.json strengthens the position of major publishers and sets highly competitive conditions for publishers with a small audience. Also, any vendor can mark an account confidential using an option within sellers.json. If they select it, this could lead to transparency blocking. But the problem is potential. Otherwise, this solution would not work at all.


Ads.txt and app-ads.txt initiatives allow checking the publisher’s direct sellers only. But they do not verify intermediary sellers on the SSP or ad exchange side. So how the advertisers can rest assured that they purchase the publisher’s inventory from the authorized reseller? And how publishers can be confident that their traffic would not fall into fraudsters’ hands?

Sellers.json and SupplyChain object solve this issue and verify all vendors who participate in the selling of a bid request. We also support the IAB Tech Lab’s implementations and facilitate cost-effective support to your business by providing safe automatization processes.

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