Thought Leadership

How Do Sellers.Json and Schain Improve Transparency for Buyers?

May 4, 2020
By John Clyman

Let’s face it, the programmatic ecosystem hasn’t always had the greatest record when it comes to transparency. But as the industry continues to mature, it’s collectively taking steps to break open the black boxes and expose the essential data that buyers need to make informed decisions.

A pair of standards that the IAB Tech Lab released last year are a big leap forward. Sellers.json and OpenRTB SupplyChain object (a.k.a. “schain”, as it appears within bid requests) together provide a way to disclose all of the parties that act as intermediaries in a bid request. This means a DSP or buyer can tell not just which exchange or SSP the inventory came from, but trace the entire payment trail back to the original content creator.

In this three-part series, we’ll discuss what you need to know about sellers.json and schain and how to use them wisely. Most importantly, when using sellers.json and supply chain to choose your preferred buying paths, it’s important to use a scalpel rather than a sledgehammer. We’ll describe why, and how to avoid some potential misinterpretations that could confuse your analysis.

Provenance Of Inventory

In the idealized world of Programmatic 101, a publisher or app developer works directly with an SSP or exchange, who in turn makes the inventory available to a DSP that bids on behalf of a buyer. Of course, in the real world, the relationships are often more complex and involve more parties.

Historically, though, a buyer typically couldn’t see more than one step beyond its DSP. They knew the DSP was buying from a particular SSP or exchange. But who was that party getting the inventory from? Hint: It wasn’t always the publisher or app developer.

In fact, a buyer purchasing an impression on a site might not know whether they were buying it via the most direct path possible, or through various other intermediaries. And when intermediaries play a role, they may or may not be adding value — though they’re almost certainly adding fees, and in some cases risk.

Schain and sellers.json have given buyers a way to reconstruct the complete supply chain, providing an essential degree of transparency, illuminating how different entities are involved and enabling more effective conversations about how those parties add value.

How It Works

Schain and sellers.json are two separate standards that work best in conjunction with each other. Sellers.json is a file that an intermediary — anyone between the original publisher, app developer, or content owner and a DSP — posts on its corporate domain. (Sellers.json, by the way, is typically pronounced “sellers dot Jason” or “sellers dot jay-sahn”; JSON is just a standard machine-readable way to structure data that isn’t specific to the ad-tech world.)

A sellers.json file names the business entities, or occasionally individuals, that the intermediary actually pays for ad spend to a given publisher ID. It also indicates whether each of those entities is itself a true “publisher” (the actual content creator) or an “intermediary” (who should post their own sellers.json file to indicate who they pay in turn). You can see Rubicon Project’s sellers.json here.

Schains are embedded in bid requests. Each intermediary that touches a bid request on its way to a DSP adds itself to the schain (as long as it’s involved in handling payment). When a complete schain reaches a DSP, it can then be cross-referenced against published sellers.json files to identify the entities receiving payment all the way back to the publisher.

Sometimes the chain will be short: If a DSP gets an schain from a Rubicon Project when we have a direct relationship with the publisher, it will only contain a single link to look up in sellers.json to confirm the publisher’s identity. But sometimes there are other participants in the payment flow as well.

In our next installment, we’ll discuss what differences in schains mean, and how to use schain and sellers.json as a scalpel, not a sledgehammer, to shape buying behavior. And in part three, we’ll dispel some common misconceptions.

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