sellers.json
A file published by an advertising system that lists the sellers it works with and whether each is a publisher or an intermediary.
What is sellers.json?
sellers.json is an IAB Tech Lab standard that lets an SSP, exchange or other advertising system publicly identify the sellers it pays. The file sits at the root of the system’s domain and lists each seller account ID, along with whether that seller is a publisher, an intermediary or both, and usually its name and domain. It complements ads.txt, in which publishers declare who may sell their inventory, and the SupplyChain object, which records each hop in a specific bid request. Together they let buyers check who is selling an impression and how many intermediaries sit between them and the publisher.
How sellers.json works
Exchanges and supply-side platforms publish the file on their own domains. Buyers read it alongside ads.txt to trace who is being paid for an impression.
- An advertising system publishes a sellers.json file on its domain listing its seller accounts.
- Each entry gives the seller ID, its type (publisher, intermediary or both) and, unless confidential, its name and domain.
- Buyers match the seller ID in a bid request against the file and against the publisher’s ads.txt.
- Buyers use the result to judge the supply path and decide whether to bid or prefer a more direct route.
Why it matters
It gives buyers a view of the supply chain behind a bid request, which supports decisions about which paths to buy through.
For advertisers
It helps buyers avoid unknown resellers and concentrate spend on transparent, efficient paths to publishers.
For publishers
Being clearly listed as a publisher in partners’ files supports buyer trust and inclusion in supply path optimisation.
For adtech platforms
Maintaining an accurate file is part of being considered a trustworthy supply partner.
Practical example
A buyer sees that a seller is listed as an intermediary and chooses a more direct path to the same publisher.
Key considerations
- Entries marked confidential hide seller names, which limits transparency for buyers.
- The file must be kept in sync with account changes, or buyers may see mismatches and stop bidding.
- sellers.json shows relationships but does not by itself prove an impression is valid; it works alongside fraud detection.
More Advertising Technology terms
Frequently asked questions
What is the difference between ads.txt and sellers.json?
ads.txt is published by the publisher and lists who may sell its inventory; sellers.json is published by the selling system and lists who it pays.
Where is a sellers.json file found?
At the root of the advertising system’s domain, at the path /sellers.json.
What does seller type intermediary mean?
It means the account resells inventory owned by others, rather than owning the inventory itself.