It is estimated that 18% of programmatic impressions in the United States are fraudulent and that ad fraud was at risk of reaching $88 billion in 2023. As payments pass through numerous intermediaries, costs increase and it becomes less clear how the revenue is distributed among the parties involved. This undermines trust in the market for both buyers and sellers.
To address these problems, the IAB developed several industry standards. Ads.txt was introduced in 2017, followed by sellers.json and the SupplyChain Object in 2019. The common purpose of these standards is to improve transparency by allowing advertisers to identify authorised sellers and understand where they are positioned within the supply chain. In this article, we will discuss what sellers.json is, how it can be used through Google Ad Manager, its relationship with ads.txt and the SupplyChain Object, and future developments in this field.
What Is Sellers.json?
A sellers.json file can be defined as a JSON-formatted document hosted by an SSP, exchange, or advertising technology provider that lists direct publishers and intermediary sellers offering inventory through the platform. The file contains seller-specific fields such as seller_id, name, domain, and seller_type. This information helps advertisers identify who receives payment and filter out fraudulent sellers. The file is hosted by the service provider rather than on the publisher’s own server.
File Structure
Sellers.json consists of a JSON object containing top-level metadata and a sellers array. The top section includes contact information, such as contact_email and contact_address, as well as the version of the file. The sellers array contains objects that define each seller through fields such as seller_id, name, domain, and seller_type.
seller_id: The seller’s unique identification number. On Google platforms, this corresponds to the publisher_id of an Ad Manager, AdSense, or AdMob account.
seller_type: Indicates the seller’s role. PUBLISHER refers to a seller that directly sells its own inventory, INTERMEDIARY refers to a seller that brokers inventory belonging to other parties, and BOTH refers to sellers that generate revenue from both their own inventory and the inventory of sub-publishers.
name and domain: Show the seller’s commercial name and primary domain.
is_confidential, optional: This field can be set to “true” when the seller’s name must remain confidential.
is_passthrough, optional: Indicates that the seller acts only as an intermediary without receiving a commission, such as a technology provider.
comment and ext, optional: Used for additional explanations or custom extensions.
Google Ad Manager users can hide their name and domain information by using the is_confidential field. However, the wider industry objective is to achieve complete transparency.
You can review Amazon’s file as an example:
https://aps.amazon.com/sellers.json
{
"version": "1.0",
"sellers": [
{
"seller_id": "17b4a302-4ad3-4356-be0c-073b33912fab",
"seller_type": "intermediary",
"is_confidential": 1
},
{
"seller_id": "88d0444f-5b3c-4c8e-812e-5dc4eb581ffe",
"name": "rg_EU_GB",
"domain": "rg.abc.com",
"seller_type": "intermediary"
},
{
"seller_id": "3286",
"name": "Curiosity Media, Inc.",
"domain": "curiositymedia.com",
"seller_type": "publisher"
},
{
"seller_id": "0d6e0121-c083-470b-9721-963c41b21da6",
"name": "Curiosity Media, Inc.",
"domain": "curiositymedia.com",
"seller_type": "publisher"
}
]
}
How Does Sellers.json Work?
Sellers.json enables seller verification before an auction takes place. A DSP downloads and stores the relevant SSP’s sellers.json file, then uses the seller_id included in the bid request to identify the seller, its domain, and its type. This method allows verification to take place outside the bid request without creating additional data overhead. Sellers.json also works together with the SupplyChain Object, which lists all intermediaries in the supply chain as nodes during each advertising request and provides greater transparency.
The buyer first checks the publisher’s ads.txt file to determine which SSPs or demand partners are authorised. The buyer then verifies the seller_id through sellers.json and finally checks whether all intermediaries listed in the SupplyChain Object are authorised and charging reasonable fees. If there is an inconsistency between ads.txt and sellers.json, or if the number of intermediaries is unnecessarily high, the DSP may decide not to place a bid. Through this cross-checking process, domains selling fraudulent inventory can be identified and excluded from the system.
Difference Between Sellers.json and Ads.txt
Ads.txt is a text file hosted by publishers on their own websites that lists the SSPs or demand partners authorised to sell their inventory. Sellers.json, on the other hand, is hosted by an SSP or ad server platform and contains identity information about sellers. Ads.txt answers the question, “Who is authorised to sell?”, while sellers.json answers, “Who receives the payment?” Using both files together provides buyers with complete visibility by matching authorised sellers with the parties that ultimately receive payment.
The Role of the SupplyChain Object
The SupplyChain Object is transmitted through the schain parameter in OpenRTB 2.5 and lists each intermediary or payment point as a node. Google Ad Manager automatically adds all intermediaries that sell the publisher’s inventory, while only parties receiving payment are included in the chain. Technical service providers are excluded. If a publisher accesses Ad Exchange through a parent publisher under Multiple Customer Management, or MCM, the seller_id of that parent publisher must also be included in the chain. This allows advertisers to see the parent publisher and sub-publisher relationship through which the inventory is offered.
Google Ad Manager and Sellers.json
Google Ad Manager, AdSense, and AdMob users can allow their information to appear in sellers.json by enabling the “Provide seller information visibility” setting under Admin > Global Settings. Users enter the seller type, PUBLISHER, INTERMEDIARY, or BOTH, together with the commercial name and domain, and can also choose whether the information should remain confidential. The system determines seller_type automatically. Primary partners working through MCM are generally classified as INTERMEDIARY or BOTH.
Relationship with Multiple Customer Management, MCM
Google’s Multiple Customer Management model, introduced in 2021, replaced the former SPM programme and established a new structure for sub-publishers accessing Ad Exchange. Under MCM, a primary partner manages the inventory of connected sub-publishers through either “Manage Account”, which provides full account management, or “Manage Inventory”, which covers inventory sales only. This structure works together with ads.txt and sellers.json to show which sub-publishers are authorised and who receives payment. MCM is available to publishers that meet specific quality and policy requirements.
The SupplyChain Object shows every layer covered by the MCM relationship. Sub-publishers must therefore provide their seller_id values to the primary publisher and list authorised accounts in their ads.txt files.
Keeping the File Up to Date
Creating a sellers.json file is not sufficient on its own. It must be updated whenever seller information changes or new sub-publishers are added. For example, Forrester’s 2023 SSP report reportedly evaluated providers without a sellers.json file negatively because buyers had difficulty distinguishing direct sellers from intermediaries. This demonstrates the importance of keeping the file accessible and up to date.
Supply Path Optimisation, SPO
SPO is a process designed to eliminate unnecessary intermediaries by helping DSPs reach inventory through the shortest and most efficient route. Algorithms analyse the fees and transparency associated with each supply path and select the most direct available route. Because header bidding implementations often create multiple paths to the same inventory, SPO helps reduce this complexity.
For publishers, SPO can lead to higher fill rates, increased revenue, and simpler reporting. For advertisers, it can provide lower costs, greater transparency, and improved performance. However, implementing SPO also creates challenges such as integrating data, developing algorithms, and coordinating with stakeholders throughout the supply chain. Sellers.json and the SupplyChain Object provide the data required for this optimisation and help DSPs avoid unnecessary intermediaries.
The Future: Buyers.json and the DemandChain Object
In addition to seller-side transparency, the IAB is developing the buyers.json and DemandChain Object standards to improve visibility on the buyer side. While sellers.json identifies the seller, buyers.json shows which buyers are placing bids, making both sides of the auction more transparent. Wider adoption of these standards is expected to strengthen trust throughout the programmatic ecosystem.
Benefits and Challenges of Sellers.json
Transparency and trust: A visible supply chain allows advertisers to understand where their budgets are going and helps remove fraudulent inventory. Providers such as MGID emphasise that sellers.json and the SupplyChain Object increase buyer confidence and can provide an advantage to early adopters.
Increased revenue and brand reputation: A transparent structure allows brands to invest with greater confidence and may increase publisher revenue by reducing unnecessary commissions.
Reduction of fraud: When ads.txt, sellers.json, and the SupplyChain Object are used together, they make it easier to identify fraudulent domains and unauthorised sellers.
Supply path optimisation: DSPs can use this data to analyse the supply path and choose the most suitable route with the fewest possible intermediaries.
However, implementing and maintaining these systems requires technical knowledge, and the process may be complex for smaller publishers. Some sellers may want to conceal their identities through the is_confidential field, which makes it difficult to balance transparency and privacy. The files also need to be updated continuously. Otherwise, inaccurate information may cause DSPs to stop bidding. In addition, sellers.json is not mandatory, meaning it may not be adopted by every participant in the ecosystem.
Conclusion
The lack of transparency in the programmatic advertising market negatively affects both advertiser spending and publisher revenue. Standards such as sellers.json, ads.txt, and the SupplyChain Object work together to address this problem. Ads.txt lists authorised sellers, sellers.json identifies the parties receiving payment, and the SupplyChain Object records the entire chain during each auction request. Together, these three standards help identify fraudulent sellers, remove unnecessary intermediaries, and optimise supply paths.
Publishers using Google Ad Manager should participate in this transparency initiative by entering accurate seller information and ensuring that their MCM structures are aligned with ads.txt and sellers.json. Regularly updating sellers.json files increases DSP confidence and reduces the risk of fraud. As future standards such as buyers.json and the DemandChain Object become more widely adopted, both sides of the auction chain will become easier to track, improving the overall reliability of the programmatic advertising market.
