Posted on Jun 27, 2023

What is Sellers.json: A Guide to Transparency in Programmatic Advertising

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For many marketers, ad fraud tops their list of challenges when it comes to advertising. In fact, a Forbes study identified fraudulent traffic as one of the most significant difficulties with digital advertising in recent years. This is no surprise, as Juniper Research estimates that the cost of ad fraud in 2022 will reach a high of  $87 billion. To put this in perspective, Invesp asserts that for every $3 spent on digital ads, $1 is lost to fraud.

Despite the unpleasant realities, stakeholders in the digital advertising industry are continually inventing to eradicate or minimize the frequency of ad fraud to the bare minimum. Do not hesitate to explore our article about the top programmatic advertising trends.

Over the years, several standards have been implemented to combat fraud; one of such mechanisms is the sellers.json introduced in 2019 by the Interactive advertising bureau (IAB). IAB introduced the sellers.json as a protocol that would complement other existing standards like the ads.txt in the fight against ad fraud.

This guide describes the sellers.json protocol, how it works, and its benefits for Smarthub owners. Read on to learn more about this technology and how to implement it on SmartHub for establishing a secure and transparent marketplace.

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What is Sellers.json?

Sellers.json is a file that contains a list of all digital ad sellers who have been approved by an ad tech platform (typically SSPs and ad exchanges). The JSON file, which is hosted on the supply side platform, contains all of the information necessary for digital buyers to identify the digital sellers with whom they are transacting, including direct sellers and intermediaries. The sellers.json functions together with the SupplyChain object.

With the SupplyChain object, media buyers can identify the entity or parties involved in selling or reselling inventory (information is contained in the bid request). Having this information is necessary to promote ad tech transparency measures and give buyers more control over how they spend their ad budget because it makes them aware of the supply chain, the parties involved, and the bidding process. The ultimate goal of the sellers.json standard is to make ad purchasers aware of who they are dealing with and to make media trading more transparent.

Sellers.json integration became necessary because the supply side of the programmatic system is sometimes inundated with various resellers and intermediaries, resulting in a long, complex chain of inventory supply. Without sellers.json, it becomes easy for fraudsters to join the complex ad digital advertising supply chain and fleece unsuspecting buyers of their ad money.

The sellers.json is often confused with ads.txt; they are not the same thing even though they share some similarities.

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Sellers.json VS Ads.txt

Ads.txt is a text file that publishers create to combat ad fraud. It allows publishers to specify authorized inventory sellers for their ad inventory, providing programmatic advertising transparency for buyers to verify legitimate vendors. This file is publicly accessible, enabling buyers to confirm they are dealing with an approved seller according to the publisher’s specifications.

In comparison, sellers.json serves as an extension of ads.txt, but it is hosted on the website of the Supply-Side Platform (SSP) or ad exchange. The purpose of sellers.json is to address a potential limitation of ads.txt. While ads.txt focuses on authorized inventory sellers declared by publishers, it may not capture all legitimate resellers, particularly those who buy and resell inventory on exchanges. Sellers.json provides a more comprehensive view by disclosing all the parties involved in selling a publisher’s ad inventory, including intermediaries who may not have a direct connection to the publisher.

By leveraging sellers.json, advertisers can gain insights into the complete digital advertising supply chain and identify all participants in the transaction, ensuring programmatic advertising transparency and minimizing the risk of fraudulent activities. This additional level of detail helps advertisers make informed decisions about their ad purchases and validates the legitimacy of the entities involved in the advertising ecosystem.

Explore more information describing sellers.json vs ads.txt.

What to choose?

When deciding whether to use sellers.json, ads.txt, or both, publishers and buyers should consider their specific needs and goals. Here are some insights to help determine the appropriate implementation:

Ads.txt only: If the primary concern is to combat ad fraud by ensuring that only authorized sellers are allowed to sell the publisher’s ad inventory, then implementing ads.txt alone can be sufficient. This approach is suitable when there is no requirement for a granular view of the supply chain or when the publisher doesn’t rely heavily on intermediaries.

Sellers.json only: If the publisher wants to gain a more detailed understanding of the supply chain and the entities involved in selling their ad inventory, implementing sellers.json becomes important. This is particularly relevant when the publisher works with numerous intermediaries or resellers and wishes to validate their legitimacy. Sellers.json provides additional insights and programmatic advertising transparency beyond what ads.txt offers.

Both ads.txt and sellers.json: Implementing both ads.txt and sellers.json is ideal for publishers and buyers seeking maximum transparency and ad fraud prevention. Ads.txt ensures authorized sellers are designated, while sellers.json provides a deeper view into the digital advertising supply chain, capturing intermediaries and all parties involved in selling the ad inventory. This combination allows for comprehensive verification and minimizes the risk of fraud or unauthorized activities.

How Sellers.json works

The sellers.json serves as an authenticating resource that identifies all the adtech participants involved in a bidding auction selling process. The SSPs and ad exchanges are mandated to list all their approved resellers and publishers, including adding other relevant information like the seller’s ID that enables easy identification. Each seller ID must be matched to an individual reseller or publisher, implying that each reseller or publisher cannot have more than one seller’s ID.

The sellers.json file might include multiple fields, some of which are required and others dependent on what the seller wants to share.

The following entries should be included in the seller’s.json file:

 sellers.json file on SmartHub - example

5 Benefits of Sellers.json

Here are some important benefits of sellers.json.

Enhanced supply chain management

With the sellers.json, advertisers and DSPs will be able to identify lengthy digital advertising supply chain and avoid it. The more resellers are on a supply path, the more costly it would be to buy the end seller’s (publisher) inventory. Besides, every buyer hopes to get the best value for their budget, so it becomes important to examine the sellers.json to identify more efficient supply chains.


The multiplicity of actors in the supply side of programmatic advertising led to complexities and a lack of clarity on who the real ad tech supply-side partners are. Sellers.json alongside ads.txt was initiated to provide some clarity and amplify ad tech transparency measures on the parties involved in selling an inventory. With sellers.json, advertisers can now clearly identify selling partners and gain a better understanding of the entire ad buying process.

Increased revenue for publishers

Publishers also benefit from sellers.json because it allows them to receive their entire income by identifying inventory selling partners who have a smaller and more efficient digital advertising supply chain. If the supply chain is extensive and includes a lot of needless intermediaries, the publisher will lose a significant portion of inventory revenue to these many supplier partners.

Trust and Brand Safety

Sellers.json promotes trust and brand safety by enabling advertisers to make informed decisions about the entities they work with. With authorized inventory sellers advertisers can ensure that their ads are being displayed in environments that align with their brand values and avoid potential association with fraudulent or low-quality inventory sources.

Compliance with Industry Standards

Sellers.json aligns with industry efforts to increase programmatic advertising transparency and combat ad fraud. Sellers.json implementation demonstrates a commitment to best practices and helps build trust among industry stakeholders.

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How to Generate Sellers.json on SmartHub?

In order to set up Sellers.json, you need to select the company in the ‘Companies’ section. Pay attention to the Domain column. Note that some companies do not have domains:

Add company domain on SmartHub

Companies without domains appear in Sellers.json with an ID but without the domain.

Open the profile of each SSP company without the domain, and add it:

Open the profile of each SSP company without the domain, and add it

Then, open Settings.

To set up the Sellers.json correctly on SmartHub, you will need to fill in the fields with your contact details and main company domain.

Fill in the fields with your contact details and company domain

Click ‘Download file’ and move to the next step: place the file on your domain.

How to use Sellers.json. After the Sellers.json file is downloaded in the settings of Sellers.json it should be placed on the company domain.

Together the ads.txt and sellers.json files should have unified IDs that are passed in the Schain object in the requests, that can be checked on public domains, for inventory transparency of the market players like advertisers, publishers, and resellers.

Sellers.json example: records listed as JSON objects

Sellers.json must contain records listed as JSON objects:

"contact_address":"New York 5555",
"identifiers": [
"sellers": [
"domain":" may be for sale - "

The main object contains the contact info of the Sellers.json issuer, the version of the file, and identifiers, such as TAG-ID.

The sellers’ array must contain objects for each partner. Such an object consists of fields seller_id, seller_type, seller_name, and domain, and also an optional is_passthrough field.

If everything is correct, place the file in the root directory of your main domain, so your partners can scan the file, and scan other Sellers.json files down the supply chain.

For example, if the platform URL, Sellers.json should be added to the  domain, so the resulting address should be

Supply Chain Object

If set, each bid request will contain the Schain object that reveals the entire supply chain The request will look like this:

"bidrequest" : {
"id": "BidRequest2",
"app": {
"publisher": {
"id": "aaaaa"
"source": {
"ext": {
"schain": {
"complete": 1,
"nodes": [
"asi":" domain name is for sale. Inquire now. ",

"asi":"Reseller Solutions at ",

The Schain object, as shown above, contains the specification version, the completion flag, and an array of nodes. Each node corresponds to a reseller that is a link in a supply chain. The first node represents the initial advertising system that received the request.

Let’s take a closer look at the object. It contains such fields:

asi – The domain name of the advertising system intermediary.

Note: This should be the same value as used to identify sellers in an ads.txt file if one exists.

sid – The identifier of the seller or reseller account within the advertising system.

rid – The request ID as issued by the seller or reseller.

hp – Flag of involvement in the flow of payments.

Note: This field is required and should always be set to 1.

An example of building a supply chain object:

The issues a bid request.

The request was received by SSP1.

Then, the request transmitted sequentially:

  • to Exchange Platform 1
  • to Exchange 2

And finally, the request comes to DSP1, which responded with a bid response.

The final supply chain object will look like:

"nodes": [
"asi":" ",
"asi":" ",

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To conclude

Sellers.json was initiated to encourage transparent dealings between media buyers and sellers, also enabling buyers to identify fraudulent supply chains. While this is an effective tool that has proven beneficial, advertisers and publishers shouldn’t rely on only this tool but utilize it together with other ad fraud prevention mechanisms to optimize the entire programmatic ad value chain and reduce ad-related losses.


What is the purpose of sellers.json in the ad tech industry?
The purpose of sellers.json in the ad tech industry is to provide programmatic advertising transparency and accountability by disclosing the entities involved in selling digital advertising inventory. It helps buyers verify the legitimacy of sellers and understand the supply chain, fostering a more trusted and efficient ecosystem.
Can sellers.json help in reducing ad fraud?
Yes, sellers.json can help in ad fraud detection and reducing it. By revealing the authorized sellers involved in the ad supply chain, it enables buyers to identify unauthorized intermediaries or suspicious entities. This programmatic advertising transparency makes it easier to detect and mitigate ad fraud, ensuring that advertisers’ budgets are spent on legitimate and trustworthy inventory sources.
How can a White Label Ad Exchange Platform implement sellers.json?
To implement sellers.json, a White Label Ad Exchange Platform needs to ensure that its platform provides clear and accurate information about authorized inventory sellers. It should disclose the seller’s domain, ID, and any resellers involved in the supply chain. By adhering to the sellers.json specification and regularly updating the file, the platform promotes transparency and builds trust with buyers.
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