What is Sellers.json and why does it matter?
Sellers.json is an IAB-defined transparency standard that works alongside ads.txt and app-ads.txt to help DSPs verify which ad-tech partners are authorized to monetize what inventory. It's a simple JSON file you host on your advertising system's operational domain at */sellers.json (for example, example.com/sellers.json). The file lists all publishers and ad-tech providers your system works with, along with metadata about each one.
Maintaining an accurate sellers.json is critical to performance. All major DSPs validate your ads.txt and app-ads.txt entries against your sellers.json file when making purchasing decisions. Gaps or mismatches between these files can negatively impact how Buyers interact with your inventory. Think of sellers.json as the reference layer that closes the loop between you, your publishers, and the buyers purchasing your inventory.
What information should be in each sellers.json entry?
Each entry in your sellers.json file should include four key fields:
domain — The operational domain of the ad-tech partner (without protocol or subdomains). This must match the domain listed in the ads.txt and app-ads.txt entries where you’re authorized, or the OWNERDOMAIN or MANAGER domain if you own or exclusively manage monetization for your properties. This helps buyers identify who they're actually buying from in the auction.
name — The partner's legal business name. This provides context for buyers who may not immediately recognize an operational domain. If your partner's domain is technical or abstract, their legal name makes it obvious who you're working with.
seller_id — The partner's unique identifier within your platform. This must match the identifier in your ads.txt and app-ads.txt entries. It helps buyers verify they're purchasing from an authorized source and that the inventory they're buying matches how you’re authorized to monetize the inventory you send.
seller_type — How you access the publisher’s inventory. Use one of these values:
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PUBLISHER — The partner owns the inventory they're monetizing and you work with them directly
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INTERMEDIARY — The partner resells other publisher’s inventory on your platform
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BOTH — The partner owns some inventory and resells other inventory (or create separate entries for each)
Buyers prefer shorter chains of participants, so accurate seller_type values help them understand the transaction structure.
Why is sellers.json accuracy so important?
Mismatches or outdated information between your sellers.json, ads.txt, and app-ads.txt can trigger validation failures at the DSP level. When a DSP can't verify your supply chain, they may pass on your inventory entirely, bid less often, and/or bid with lower CPMs. You should review your sellers.json regularly and add or remove partners as your partnerships change.
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