Viewing authorized sellers

Publishers work with various partners, such as SSPs, exchanges, and ad networks, to sell their ad inventory to buyers. Since there can be many sellers that participate in the selling of a bid request, the IAB developed these three specifications to help identify authorized sellers of a bid request: Authorized Digital Sellers (ads.txt and app-ads.txt), Sellers.json, and SupplyChain. Publishers can use these specifications to make sure that they are transparent in selling ad space and compliant with industry standards. This compliance and transparency framework helps with the following:

  • Prevent domain or app spoofing and unauthorized reselling of inventory from fraudulent and malicious actors.

  • Preserve the value of domains and apps for publishers, while maintaining trust with buyers.

Ads.txt and app-ads.txt

Publishers selling ad inventory for the web must implement an ads.txt file, and publishers selling inventory for mobile app and CTV must implement an app-ads.txt file. This is to help buyers identify all the seller accounts that are authorized to sell a publisher's ad inventory. Every publisher working with Index is required to add their unique Index account entry as an authorized seller in their ads.txt or app-ads.txt files. To view your ads.txt entry in the Index UI, see View your Index ads.txt entry.


The following is an example of the seller information available for a given seller in an ads.txt or app-ads.txt file:, 678901, DIRECT, 50b1c356f2c5c8fc

For more information on our ads.txt and app-ads.txt policy, see Ads.txt and app-ads.txt exchange policy.

Sellers.json and SupplyChain

Similar to ads.txt and app-ads.txt, Sellers.json is a JSON file that SSPs and exchanges must implement to list all the authorized sellers that are involved in the selling of a bid request. Through the SupplyChain object, Sellers.json covers the multiple hops between SSPs and other sellers in the selling of ad space that ads.txt and app-ads.txt does not cover.


"sellers": [
	  "seller_id": "123456",
	  "name": "Publisher ABC",
	  "domain": "",
	  "seller_type": "Publisher"
	  "seller_id": "123457",
	  "name": "Seller XYZ",
	  "domain": "",
	  "seller_type": "Intermediary"
	 "seller_id": "123458",
	 "name": "Platform 123",
	 "domain": "",
	 "seller_type": "Both"

Index's Sellers.json file is located here:

SupplyChain refers to the schain object located in the source ext of an OpenRTB bid request that allows DSPs to see all parties who are selling or reselling a given bid request. When an authorized seller, such as IX, receives a bid request, they add their information as a "node" to the schain.nodes object to identify that they are an authorized seller involved in the selling of a bid request.


The following is an example of an schain object getting passed in a bid request to DSPs.

"source": {
     "ext": {
	 "schain": {
	   "nodes": [
	       "hp": 1,
	       "sid": "192354",
	       "rid": "000256f1-nov5-43le-4fds-0417cf186e56",
	       "asi": ""
	   "ver": "1.0",
          "complete": 1

When a DSP receives a bid request from Index, they can identify the sellers referred to in the schain and nodes objects by comparing it to the seller information listed in the Index Sellers.json file.

All authorized sellers are required to pass the schain object. To be considered an authorized seller, the ads.txt or app-ads.txt entries should match the values passed in the schain object. For more information, refer to the table below.

Field in ads.txt or app-ads.txt Corresponding field in schain object

SSP or exchange domain. This is the site for the SSP or exchange. For example,


Seller Account ID. This is the seller’s account ID assigned to a publisher. For example, 183963.



The following are examples of how an authorized seller’s entry should be formatted in a publisher’s ads.txt file to match the corresponding fields passed in the schain object:

asi, sid, DIRECT or asi, sid, RESELLER