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All You Need to Know About Sellers.json

All You Need to Know About Sellers.json

4 Minute read

Advertisers want to be confident that they are maximizing the value of every dollar they spend on media. In many cases, there are several players taking a cut of the ad revenue on the way to the publisher. Not always for good reason. The length of the supply-chain has become a big deal for both ad buyers and publishers.

An important study of programmatic supply chain costs showed that as much as a third of the costs are unattributable. By passing through the hands of multiple resellers, just 51% of digital ad spend was getting to the publisher. That is wasteful for the industry as a whole.

Sellers.json and SupplyChain Object

Launched in July 2019 as a standard category by the Interactive Advertising Bureau (IAB), Sellers.json was introduced to give advertisers transparency into the buying chain that their ad dollars travel on the way to the publisher.

The Sellers.json is a JSON file hosted in the media seller’s home page URL, which contains all its seller authorized media sources, each marked as either Owned & Operated or Intermediate. The SupplyChain Object is the technical parameter sent in each ad call and it indicates all intermediates involved in the transaction leading back to the publisher.

The serious push towards transparency was introduced with the ads.txt initiative, which was created to help prevent domain spoofing and unauthorized reselling of inventory.

Publishers and ad tech vendors often work with other intermediaries and resellers, which turns the ad tech landscape into a complex web. An Association of National Advertisers study uncovered just how complex the supply chain is. Over 260 Million impressions were analyzed, and only 12% of them could be mapped. Of 15 advertisers that were studied, researchers identified nearly 300 distinct supply chains leading to just 12 publishers. Sellers.json allowed ad buyers to see the complete media chain.

How Sellers.json Works

The sellers.json file can contain several fields, some are mandatory and others are dependent on what the seller would like to share. Bear in mind that sharing more details can impact the buyer’s buying decision. Here is an example:

"seller_id": "12345",

"name": "Best Media Publisher",

"seller_type": "PUBLISHER",

"is_confidential": 0,

"is_passthrough": 0,

"domain": ""

The information is passed to the buyers by using the OpenRTB Supply Chain Object (Schain) parameter. This parameter is required and should be passed on for each ad call.

3 Reasons Why Sellers.json Is So Important


The ads.txt initiative was an important move towards making the industry supply chain more transparent, but it was not enough. The initiative shows which vendors are allowed to sell a publisher’s inventory. However, it doesn’t give information on who is listed behind the ads.txt line or who is actually paying the publisher. Sellers.json fills in that gap by letting buyers understand the full buying chain and make smarter decisions when choosing the most valuable partners to purchase media from.

Supply Path Optimization (SPO)

Advertisers, and media buyers on their behalf, want to reach their audience in the most efficient way possible. With sellers.json, that is possible. Buyers can analyze their supply path and focus their efforts on paths that give them the most value for every media dollar spent.

An additional advantage for Demand Side Platforms (DSPs), and eventually for buyers, is the ability to reduce the number of Queries Per Second (QPS) they receive. Many DSPs get the exact same ad request/query from many sources, which inflates their serving costs. A transparent buying chain can help them cut longer and wasteful chains, allowing them to reduce the number of calls and costs. The reduced costs for the DSP can ultimately lead to lower costs for buyers.

Publishers Receive Much Needed Ad Revenue

When transparency is introduced to ad sales, sellers have the ability to prioritize shorter and more efficient supply-chains. More efficient supply-chains mean less commission cut along the way and publishers will get more of the ad revenue.

Also, DSPs such as TheTradeDesk, adopted these initiatives and will not buy inventory without a valid entry in the relevant sellers.json file.

What’s Next?

The IAB Tech Lab isn’t resting and just recently launched the first version of Buyers.json and DemandChain Object. These two new buy-side transparency standards aim at helping publishers and Supply Side Platforms (SSPs) to more easily identify buyers across multiple demand sources, while protecting themselves and their users from malvertising and nefarious ads.

Like Sellers.json and SupplyChain Object provided the buy side with transparency into who they are buying their media from, Buyers.json and DemandChain Object will provide similar transparency to the sell side.

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