Sellers.json and SupplyChain


As part of the industry initiative to increase trust and transparency in the ecosystem, the IAB Tech Lab has released the Sellers.json and SupplyChain specification. The goal is to be able to connect ads.txt, Sellers.json and SupplyChain together to understand the flow of revenue for an impression. These specifications only apply to resellers, publishers do not need to take any further action unless they have resellers using the same client side Prebid adapter as their resellers.

Industry Support

Improve Digital supports Sellers.json and SupplyChain. Demand partners including The Trade Desk use these standards to as key factors in determining bidding behaviour. DV360 is planning to introduce validation in 2021, by the end of Q3 2021 blocking bid requests with unauthorised or missing SupplyChain nodes, and end Q4 2021 blocking bid requests without a SupplyChain.


  1. create a sellers.json file, based on the IAB specification
  2. configure the integration to pass Improve Digital the SupplyChain depending on your integration type with Improve Digital:
    1. Prebid: update to the latest version of the Improve Digital adapter, and follow the specification for enabling schain.
    2. oRTB Server to Server: available, see IAB sellers.json specification and IAB GitHub specification. Example:
      "schain" : {
    3. Tags
      A new optional get parameter called schain should be added. The value should conform to the IAB serialization specification. For example:


The seller ID in each node must be present in the publisher ads.txt file in order for the SupplyChain to be correct, and the first node must be marked as DIRECT.


The following checks are made by DSPs:

  • Check the supplychain is correctly formatted and can be parsed
  • Ads.txt records for a given domain/app should be present for upstream nodes in the SupplyChain for that domain/app. Note that this is expanded guidance from the existing ads.txt spec, but should be considered a best practice.
  • For a given node, the name associated with a seller ID (from sellers.json) on a given advertising system should match the advertising system in the preceding node. Otherwise, it implies a break in the chain.
  • In cases where the complete flag is set, you can check that the first node has a seller type of PUBLISHER. If it does not, there must be one or more missing nodes.
  • Check that the first node of the SupplyChain object is listed as a DIRECT seller in the publisher’s ads.txt file. It should be in most cases. If it's not, consider one of the following two reasons:
    • The actual first node has been removed from the chain (SupplyChain has been tampered with)
    • The publisher has incorrectly listed the record as RESELLER in their ads.txt file

Sellers using Google Open Bidding (EBDA)

Publishers who use Open Bidding to send inventory to Improve Digital from their own Google Ad Manager account have no further action to take, as Google will automatically add their schain node in the ad request.

Sellers who operate Google Ad Manager accounts on behalf of multiple publishers (and pay publishers from the revenue received in their account), therefore exchange yield partners, will need to add their additional schain node, which is sent with Google's to Improve Digital. See Google Open Bidding documentation.

Client-side Prebid for Resellers

There are configurations where a publisher has the Improve Digital Prebid adapter connected to their own direct account, and also makes some formats available via a reseller who also uses Improve Digital in another account. This will cause a conflict in which the requests to Improve Digital for the reseller inventory will not contain the correct reseller supply chain node.

To resolve this the publisher can use Prebid's Alias feature to configure specific settings for schain, that will differ from the other adapter settings because publishers do not need to specificy schains with their SSP.

Setting up Prebid for resellers

  1. Publisher adds an alias name to the reseller's placements in the Improve Digital adapter following the Prebid documentation. For example, the publisher can add the alias imprresellername.
  2. Then the publisher can configure a bidder specific supply chain for that alias, as described in Prebid documentation.
  3. The publisher should ensure their ads.txt contains all of the following:
    1. their own Improve Digital account as DIRECT
    2. their account ID on the reseller as DIRECT
    3. the resellers Improve Digital account as RESELLER
  4. The reseller should ensure they have:
    1. A sellers.json file on their own company domain with the publishers account ID
    2. A listing on Improve Digital sellers.json with their Improve Digital account ID and correct company domain
    3. The publisher configuration is correct as in step 3.

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