What is Sellers.json?
Sellers.json is a tool to bring transparency in the digital supply chain by enabling buyers to know all the resellers involved in selling a publisher’s inventory. As we know, in many cases a publisher’s inventory is sold by many vendors – direct, first reseller, second reseller and so on. It is quite difficult for buyers to know if the final seller is authorized by the publisher to sell his inventory. Ads.txt has helped to identify the vendor’s publishers have authorized to sell their inventory, however, it lacks transparency when multiple vendors – SSPs/Exchanges are involved in selling the same impression. Sellers.json aims to fight fraud that might crop in due to this intricate chain of vendors involved in the sale of every impression.

How does Sellers.json work?
All Supply Side Platforms (SSPs) and Exchanges are expected to host a seller.json file that will include information (seller Ids, names, etc) of all the sellers – direct or indirect that an SSP/Exchange is working with. This JSON file can be accessed publicly and will enable buyers to review all the sellers. You can read more about the specs & implementation here: https://iabtechlab.com/wp-content/uploads/2019/04/Sellers.json-Public-Comment-April-11-2019.pdf

The JSON file format needs to be hosted as www.chocolateplatform/sellers.json / www.ssp1.com/sellers.json

What is OpenRTB Supply Chain Object?
OpenRTB Supply Chain Object works in tandem with sellers.json. With the same goal of adding an extra layer of transparency and demystifying the complex web of multiple resellers, it enables the buy side to examine all the parties who are selling or reselling a given bid request. Acting as a record for every impression, Supply Chain Object empowers buyers to check for any fraudulent sellers/resellers and additionally know the final reseller in the chain.

How does OpenRTB Supply Chain Object work?
The SupplyChain object is comprised of a set of nodes where each node represents a specific entity that participates in the selling of a bid request. The entire chain of nodes from beginning to end would represent all sellers who were paid for an individual bid request. This object represents both the links in the supply chain as well as an indicator of whether or not the supply chain is complete. As stated in IAB’s implementation doc, the SupplyChain object should be included in the BidRequest.Source.ext.schain attribute in OpenRTB 2.5 or later. For OpenRTB 2.4 or prior, the BidRequest.ext.schain attribute should be used. Proposed Implementation: You can read more about the specs and proposed implementation here: https://github.com/InteractiveAdvertisingBureau/openrtb/blob/master/supplychainobject.md

Do Publishers need to implement anything? Add a file similar to ads.txt?
Publishers don’t have to implement anything. Unlike ads.txt which publishers hosted, sellers.json file needs to be hosted by SSPs/Exchanges. It is the responsibility of SSPs/Exchanges to implement both Sellers.json and OpenRTB Supply Chain Object.

Do DSPs/Buyers need to implement anything?
No implementation is required on the buyer side. The goal of these two new tools is to strengthen the supply side and weed out any fraudulent vendors that might crop up as sellers. However, the buy side has an important role in ensuring the success of these new tools by verifying, reviewing and examining the seller.json files of SSPs/Exchanges they work with on a regular basis.

What role do SSP/Exchanges need to play in the implementation of these tools?
All SSPs/Exchanges are expected to be ready with sellers.json files and the addition of Supply Chain Objects in bid requests. The onus is on SSPs/Exchanges to assure buyers/DSPs that every impression bought is from a legitimate seller by enabling unrestricted review of all the resellers an SSP is working with. IAB had released the draft for public comment in April, the final specs should be out anytime in June. Chocolate has already started the implementation of both these tools and should be ready for a review of buyers/DSPs by the first week of July.