SupplyChain v1.1 Puts Your Wrapper in the schain: What Changes for Sellers

On June 23, IAB Tech Lab released SupplyChain v1.1 for public comment, an update to the OpenRTB SupplyChain object that buyers use to see who is involved in selling an impression. The proposed change is simple to describe and significant in effect: in addition to the companies in the payment flow, the chain would also list entities that take technical custody of a bid request as it moves through systems such as Prebid, ad servers, server-side ad insertion platforms, SDKs, wrappers and other infrastructure. Public comment is open through August 21, 2026.

Tech Lab CEO Anthony Katsur called it “one of the most significant transparency enhancements to the digital advertising supply chain in years.”

A quick refresher on schain

The SupplyChain object, usually called schain, travels in the bid request. Each node represents a company involved in the sale and includes that company's advertising system domain, the seller ID it uses for the upstream party, and an hp flag indicating whether the node is part of the payment flow. Combined with sellers.json, which lets buyers look up who each seller ID belongs to, schain lets a buyer reconstruct the path from publisher to bidder and judge whether it is direct and legitimate.

Until now, schain has described the commercial chain. Systems that touch the request without being paid in the transaction, such as a wrapper or a server-side bidding host, generally did not appear.

What v1.1 changes

Under the proposal, custody-taking entities are added directly to the main chain, marked with hp=0 when they are not part of the payment flow. That lets buyers see which systems handled a request even when those systems do not take a cut of the media spend. Supporters quoted in the announcement made the same point in different words. Rob Hazan of The Trade Desk said “a longer chain that accurately discloses the parties involved is better than a short chain that hides important information.” Chris Kane of Jounce Media said that expanding schain to include technical custody brings the industry closer to a world where efficiency is measurable.

Coverage in MediaPost described the shift as moving supply path optimization from rewarding the shortest path to rewarding the most transparent one.

What a longer chain might look like

Consider a common web setup: a publisher runs a Prebid wrapper, and bids flow to an SSP that sells the impression to a DSP. Under today's model, the chain typically shows the SSP as the node with a seller relationship to the publisher, because it is the company that pays out. Under v1.1, the system that took custody of the request before the SSP would also appear, marked hp=0 because it does not sit in the payment flow. In a CTV setup, an SSAI platform building the request would appear the same way. Each node is a company buyers can look up and evaluate, which is the point.

Why that matters for publishers

Many buyers use schain length as a rough quality signal: short chains good, long chains suspect. Under v1.1, honest chains will get longer, because they will include the technology between the publisher and the exchange. That is only a problem if buyers keep reading length naively. The point of the change is to let them judge what each node actually does.

For publishers, it also means your technical setup becomes visible to buyers in a way it was not before. A clean setup with a well-known wrapper and a small set of partners will look clean. A setup with several layers of intermediaries touching every request will be visible as exactly that.

What to do now

1. List every system that touches your bid requests. Wrapper, Prebid Server host, ad server, mediation or SDK layer in apps, SSAI for video, and any vendor that receives and forwards requests. Most publishers have not written this down.
2. Check who has sellers.json entries. For nodes to be verifiable, the companies behind them need to be identifiable. Ask your technology providers whether they plan to support v1.1 and how they will identify themselves.
3. Confirm your current schain is correct. Before adding complexity, verify that today's chain is accurate: correct seller IDs, correct hp values, and a complete flag that reflects reality. Mistakes in v1.0 chains are common and will be more obvious in a longer chain.
4. Remove layers that add nothing. If a system is touching requests without adding demand, data or capability you use, v1.1 is a good reason to remove it before buyers ask why it is there.
5. Comment if you have concerns. Implementation details matter, especially for app and CTV setups with several technical layers. The comment window runs to August 21.

How this fits the bigger picture

SupplyChain v1.1 is part of a broader push from IAB Tech Lab this year to make programmatic more legible, alongside work on bid request efficiency and a new Programmatic Governance Council. The common thread is that buyers want to see and verify what they are paying for. Publishers who can show a clear, well-documented path will benefit; those whose setups rely on opacity will find it harder.

The takeaway

SupplyChain v1.1 would make the technology behind your inventory visible to buyers, not just the companies that get paid. Map every system that handles your bid requests, fix today's chain before it grows, remove layers that do not earn their place, and follow the comment period. A transparent path is becoming the one buyers choose.