Sellers.json: What You Need to Know

Sellers.json: What You Need to Know

4 Minute read

In digital advertising, the supply chain is very complex. In most cases, there are multiple providers in the chain that are taking their cut of the ad spend and diluting the overall buy and the ad revenue that makes its way to the publisher.

A lack of transparency has developed over the years that can obscure the pathway. As much as a third of all costs in the programmatic supply chain, for example, are unattributable according to the Programmatic Supply Chain Transparency Study. The study, conducted by PwC for ISBA, looked at 267 million impressions over 15 months and determined that publishers are receiving just 51% of the digital spend.

What Is Sellers.json?

The Interactive Advertising Bureau (IAB) thus created Sellers.json as an industry standard to help provide advertisers with more transparency into the buying process to help track where ad dollars go on their path to the publisher.

Sellers.json is a file hosted on an exchange dedicated URL containing seller-authorized media sources. They are marked as either owned and operated by the publishers or as intermediaries. The SupplyChain Object is included in each ad call, which identifies any intermediaries involved in the transaction between the advertiser and publisher.

To take part, sellers must also take part in the ads.txt initiative, another initiative from IAB Tech Lab to increase brand confidence and prevent fraud.

Why Is Sellers.json Needed?

Intermediates and resellers are not bad things alone. Publishers work with multiple partners to facilitate programmatic buying and selling, but it creates a complex chain.

Here’s an example of how complex these supply chains can be: a study by industry trade group ANA analyzed 260 million impressions and could map only 12% of them. Of the 15 advertisers included in the study, researchers found almost 300 distinct pathways.

The sellers.json file contains a list of all authorized sellers and resellers of a publisher’s inventory, allowing transparency into the supply chain. By documenting the payments in the buying process, buyers can see where their money goes.

How Sellers.json Works

There are several fields in the sellers.json file. While some are required, sellers do not have to disclose everything.

Required Fields

This information is passed to the buyers with the OpenRTB Supply Chain Object parameter for each ad call.

  • Seller_id: The same ID as appears in the ads.txt file and Supply Chain nodes
  • Seller_type: Publisher, Intermediary, or Both
  • Name: The legal entity publisher name (if confidential)
  • Domain: The business domain name

Optional Fields

This information is optional.

  • Is_confidential: 0 for not confidential, 1 for confidential
  • Is_passthrougL: 0 for a downstream system that has no account control with the seller, 1 for a seller that has an account control relationship with the seller to transact inventory
  • Comment: Any additional inventory description, such as when sellers have multiple IDs
  • Ext: Placeholder for specific extensions

Why Is Sellers.json Important for the Ad Industry?

There are three main reasons sellers.json is important to the ad industry: transparency, supply path optimization, and protecting revenue.


While the ads.txt initiative played a role in making the digital advertising supply chain more transparent, it fell short of its overall goal. While it identified which vendors can sell a publisher’s inventory, it did not provide information on who is paying the publisher, or who is listed behind the ads.txt line.

Sellers.json lets buyers see the entire buying chain. This helps them make better decisions about media purchasing.

Supply Path Optimization (SPO)

Sellers.json allows advertisers and media buyers to analyze the supply chain for efficiency. This can help to avoid buys that require multiple intermediaries and restrict the flow of ad dollars to publishers.

One other additional benefit for buyers using Demand Side Platforms (DSPs) is that the number of Queries Per Second (QPS) they receive is reduced. DSPs can often receive the same ad request from different sources, which can cause serving costs to rise depending on the path chosen. With more transparency, buyers can eliminate the chains that waste the most money, thereby reducing the number of calls and costs. Reduced costs for DSPs can ensure more of an advertiser’s dollar goes into the ad placement rather than intermediaries.

Publishers Get More Ad Revenue

With this transparency, sellers can reduce their supply chains and use the most efficient paths. This reduces the amount of commission that is siphoned off from multiple intermediaries. For advertisers, this means more of the money they are spending on ads goes toward reach rather than processing. For publishers, they capture a greater amount of ad dollars.

The Future of Ad Buying and Selling

Several of the most prominent DSPs, such as The Trade Desk, have adopted sellers.json and will not process orders without a valid sellers.json file.

The IAB Tech Lab also recently introduced buyers.json and DemandChain Object. The goal here is to help publishers and Supply Side Platforms (SSPs) to identify buyers across multiple demand sources, so they can protect themselves. By making the information transparent, the IAB helps to reduce malvertising and nefarious ads through proactive disclosure.

While sellers.json and the SupplyChain Object allow the buy side to see who they are buying from, buyers.json and the DemandChain Object provide transparency on the selling side.

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