If you’re running a website or app and monetizing with programmatic ads, you’ve probably heard about sellers.json—but what exactly is it, and why should you care?
Importantly, advertisers today are increasingly cautious about where they spend their budgets. They want to know exactly who they’re buying inventory from, and they’re actively avoiding shady intermediaries that could expose them to fraud. As a small or medium publisher, understanding sellers.json isn’t just about compliance—it’s about positioning yourself as a trustworthy partner in the digital advertising ecosystem.
Furthermore, in this guide, we’ll break down everything you need to know about sellers.json: what it is, how it works, and why it matters for your publishing business.
Contents
- 1 What is Sellers.json?
- 2 Sellers.json Examples
- 3 Why Was Sellers.json Created?
- 4 How Does Sellers.json Work?
- 5 Benefits of Sellers.json for Publishers
- 6 Future of Sellers.json in Programmatic Advertising
- 7 Taking Action: Ensuring Your Sellers.json Presence
- 8 Conclusion: Transparency as a Foundation for Trust
What is Sellers.json?
Specifically, the Interactive Advertising Bureau (IAB) created sellers.json as a publicly accessible file that lists all authorized sellers of digital ad inventory within the programmatic supply chain. Think of it as a directory that allows advertisers to verify exactly who they’re buying ads from.
In contrast, Supply-Side Platforms (SSPs), ad exchanges, and other intermediaries publish sellers.json files. These platforms list every publisher, network, and reseller they work with, creating a transparent map of the entire supply chain.
How Sellers.json Differs from Ads.txt
While both standards work together to increase transparency, they serve different purposes:
- Ads.txt: Published by publishers on their own domains, declaring which ad platforms are authorized to sell their specific inventory. It’s a publisher-side declaration.
- Sellers.json: Published by SSPs and ad exchanges, listing all the publishers and intermediaries they’re authorized to work with. It’s a platform-side verification.
Importantly, in simple terms: ads.txt lets you say “these platforms can sell my ads,” while sellers.json lets the platform say “these are all the publishers we work with.” Together, they create a complete verification chain from publisher to advertiser.
The Key Information Sellers.json Contains
Every sellers.json file includes specific details about each authorized seller:
- Seller ID: A unique identifier that matches the seller’s account
- Seller Name: The official business name of the publisher or intermediary
- Domain: The website domain associated with the seller
- Seller Type: Whether the entity is a publisher, intermediary, or reseller
- Is Confidential: An optional flag if the seller wants to keep their information private
Importantly, this standardized format makes it easy for advertisers to quickly verify sellers across multiple platforms without contacting each SSP individually.
Sellers.json Examples
For example, let’s examine what a sellers.json entry looks like in practice. SSPs publish their sellers.json files in JSON format with entries for each authorized seller.
Example Entry for a Direct Publisher:
{
“seller_id”: “pub12345”,
“seller_type”: “PUBLISHER”,
“name”: “TechNews Media Ltd”,
“domain”: “technewsdaily.com”,
“is_confidential”: 0
}
Example Entry for an Intermediary:
{
“seller_id”: “network789”,
“seller_type”: “INTERMEDIARY”,
“name”: “Digital Ad Network Partners”,
“domain”: “adnetworkpartners.com”,
“is_confidential”: 0
}
Where to Find Sellers.json Files
Major SSPs host their sellers.json files at predictable URLs. For example:
- A platform might host it at: platform.com/sellers.json
- Google Ad Manager: admanager.google.com/sellers.json
- Most platforms follow the IAB standard location format
Specifically, as a publisher, you won’t create this file yourself—your SSP partners create and maintain it with your information included. You should verify that your details appear correctly to ensure advertisers can identify you.
Why Was Sellers.json Created?
Unfortunately, the programmatic advertising industry has a fraud problem. According to industry estimates, advertisers lose billions annually to various forms of ad fraud, including domain spoofing, unauthorized reselling, and inventory misrepresentation.
The Transparency Gap Before Sellers.json
Specifically, before sellers.json existed, advertisers viewed the programmatic supply chain as essentially a black box. An advertiser might think they’re buying premium inventory from a reputable publisher, but in reality, their ads could be passing through multiple unauthorized resellers, each taking a cut while providing little value.
Consequently, the lack of transparency led to several serious problems:
For Advertisers:
- No way to verify legitimate sellers from fraudsters
- Difficulty identifying unauthorized resellers inflating costs
- Increased exposure to brand safety risks and fraud
For Publishers:
- Lost revenue to unauthorized resellers
- Difficulty building direct relationships with quality advertisers
- Damaged reputation when bad actors misused their inventory
The IAB’s Response
Moreover, the IAB Tech Lab recognized that trust was eroding in the programmatic ecosystem. They developed sellers.json as part of a broader transparency initiative that also includes ads.txt and app-ads.txt. Together, these standards establish a verification framework for participants in the ad supply chain.
The goal? Simple: give advertisers the confidence to spend more on programmatic advertising by eliminating the mystery around who’s actually selling the inventory.
How Does Sellers.json Work?
Additionally, understanding how sellers.json operates will help you appreciate why it’s become essential for publishers who want to work with quality demand partners.
The Technical Process
Step 1: SSPs Create and Publish the File
Your SSP partners (like those integrated with PubPower’s header bidding platform) maintain a sellers.json file listing all publishers and intermediaries they authorize to sell inventory. They host this file publicly at a standard URL location.
Step 2: Information Gets Indexed
Various industry tools and verification services continuously crawl and index these sellers.json files from different SSPs, creating comprehensive databases of authorized sellers across the entire ecosystem.
Step 3: Advertisers and DSPs Verify Sellers
Before purchasing inventory, sophisticated advertisers and Demand-Side Platforms (DSPs) check sellers.json files to confirm:
- Is this seller authorized by the SSP?
- Does the seller information match other verification signals?
- Are there any red flags suggesting unauthorized reselling?
Step 4: Bid Decisions Get Made
If everything checks out, advertisers proceed with confidence. If something seems off—like a seller ID that doesn’t appear in the sellers.json file—smart advertisers will avoid that inventory entirely.
The Connection to Ads.txt
Sellers.json works hand-in-hand with ads.txt for maximum transparency. While ads.txt declares which platforms are authorized to sell your specific inventory, sellers.json confirms your legitimacy within each platform’s ecosystem. Think of ads.txt as your declaration, and sellers.json as third-party verification.
When both systems align properly, advertisers gain complete confidence in the authenticity of your inventory—which translates to higher bid rates and better CPMs for you.
Benefits of Sellers.json for Publishers
Now, let’s get to what really matters: how does sellers.json actually benefit you as a small or medium publisher? The advantages are more significant than many publishers realize.
1. Build Trust with Premium Advertisers
Specifically, premium advertisers—the ones paying top CPMs—screen inventory sources carefully. A proper sellers.json listing signals that you’re a legitimate, verified publisher. This credibility can mean the difference between landing premium bids or getting filtered out completely.
As a result, when your publisher information appears consistently across sellers.json files from your SSP partners, sophisticated buyers recognize you as a trustworthy inventory source. This can lead to better fill rates and improved CPM performance as premium advertisers compete for your inventory.
Importantly, one of sellers.json’s most practical benefits is preventing revenue leakage. Without proper transparency standards, bad actors could potentially resell your inventory without authorization, pocketing a portion of what should be your revenue.
As a result, your sellers.json listing creates a clear chain of authorization. Advertisers verify that when they buy your inventory, it’s coming through legitimate channels—and your agreed-upon revenue shares remain intact.
3. Qualify for Higher-Quality Demand Sources
Moreover, many top-tier demand partners and programmatic platforms now require sellers.json compliance as a prerequisite for integration. By ensuring your information is correctly listed, you maintain access to premium DSPs with strict quality standards and direct advertiser deals that require supply chain verification.
4. Improve Your Header Bidding Performance
Header bidding relies on multiple demand sources competing simultaneously for your inventory. However, if some DSPs can’t verify your legitimacy through sellers.json, they may submit lower bids or filter out your inventory altogether.
As a result, proper implementation ensures all bidders in your header bidding setup can verify your inventory, reducing bid rejections due to transparency concerns and maintaining consistent competition across all demand sources.
5. Demonstrate Compliance and Professionalism
The digital advertising industry is increasingly regulated, with privacy laws like GDPR and CCPA setting high standards for legitimate operations. Being properly listed in sellers.json demonstrates that:
- You’re committed to industry best practices
- You operate with transparency and integrity
- You’re a professional publisher worth investing in long-term relationships
As a result, this professional positioning helps when negotiating direct deals, applying for premium ad networks, or seeking partnerships with major media buyers.
6. Reduce Exposure to Ad Fraud Allegations
Unfortunately, publishers can sometimes get caught up in fraud allegations simply by association—even when they’ve done nothing wrong. If unauthorized resellers are misrepresenting your inventory or bad actors are spoofing your domain, you could face reputational damage.
Consequently, it creates a clear verification trail showing which platforms are authorized to sell your inventory, your legitimate seller IDs across different SSPs, and your verified business information. If questions arise about inventory authenticity, sellers.json provides immediate verification that protects your reputation.
Future of Sellers.json in Programmatic Advertising
Programmatic ad buying is rapidly transforming the digital advertising landscape. For it to remain widely accepted by both publishers and advertisers, it’s essential to prioritize transparency and trust throughout the ecosystem. Industry standards like sellers.json,… set to be increasingly important in upholding these values.
With forecasts indicating that threats such as ad fraud and domain spoofing are on the rise, it’s likely that both advertisers and publishers will need to rely more on sellers.json to mitigate these risks and curb financial losses.
Looking ahead, sellers.json will likely drive substantial improvements in the integrity and effectiveness of digital advertising as a whole.
Taking Action: Ensuring Your Sellers.json Presence
So how do you make sure sellers.json is working properly for your publishing business?
Verify Your Listings
Check with each SSP you work with to confirm:
- Your publisher account is included in their sellers.json file
- Your business name and domain are listed correctly
- Your seller ID matches your account information
Most major SSPs make their sellers.json files easily accessible at their domain followed by /sellers.json.
Keep Information Current
Consequently, if you change your business structure, domain, or company name, notify all your SSP partners immediately. Outdated information in sellers.json files can cause verification failures and lost revenue.
Work with Transparent Partners
Additionally, choose SSP partners and monetization platforms that prioritize transparency. Look for partners who maintain up-to-date sellers.json files and have strong industry reputations for compliance with IAB standards.
Monitor Your Performance
Specifically, watch for positive indicators that sellers.json is working for you, such as increasing fill rates from premium demand sources, improving CPMs as more quality advertisers bid, fewer bid rejections and disqualifications, and stronger overall header bidding competition. Most header bidding platforms provide real-time reporting dashboards where you can track these metrics continuously.
Conclusion: Transparency as a Foundation for Trust
Overall, sellers.json represents a fundamental shift in programmatic advertising—from opacity to transparency, from uncertainty to verification, from fragmentation to accountability.
Importantly, for small and medium publishers, this shift creates opportunities to compete on a more level playing field. While some may view transparency standards as just another compliance requirement, forward-thinking publishers recognize them as tools that allow quality inventory to compete fairly for premium demand.
Finally, when you ensure your sellers.json presence is properly maintained across all your SSP partners, you’re building a foundation of trust that helps establish stronger relationships with advertisers and protects your revenue streams from unauthorized resellers. Understanding sellers.json is part of a broader approach to ad transparency and fraud prevention. To deepen your knowledge, explore how ads.txt helps fight ad fraud and learn more about common types of ad fraud that affect publishers.
