Sellers.json helps answer a simple question: who is really authorized to sell your ad space? In digital advertising, many providers sit in the chain, and that is not always clear. In this article, you will learn what sellers.json is and why it matters for publishers.
What is sellers.json?
Sellers.json is a file that SSPs and ad exchanges publish to list all of their authorized ad space sellers. This file is hosted on a dedicated URL of each platform, for example: ssp.com/sellers.json. These sellers can be publishers, if they own the inventory, or intermediaries, if they resell it.
It was created by the IAB (Interactive Advertising Bureau) Tech Lab as an industry standard in order to help buyers get transparency and verify that they are buying from authorized and legitimate sources.
What does a sellers.json file look like?
You can easily find any SSP’s sellers.json by adding /sellers.json to its domain. When you open it, you will see each entry in the file includes these fields:
- seller_id: the same ID that appears in the publisher’s ads.txt.
- name: the legal name of the entity that receives the payment.
- domain: the seller’s domain.
- seller_type: it can be “PUBLISHER” if it’s the owner of the inventory, “INTERMEDIARY” if it resells it, or “BOTH”.
- is_confidential: 1 if the seller’s identity is hidden, 0 if it is public.
Sellers.json vs ads.txt
We could say sellers.json and ads.txt are two sides of the same coin.
Ads.txt (Authorized Digital Sellers) is a simple text file that publishers host on their websites, listing the companies authorized to sell their ad inventory.
| Ads.txt | Sellers.json | |
| Who publishes it | Yayıncılar | SSPs and ad exchanges |
| Main goal | To let publishers declare which SSP accounts are allowed to sell their ad inventory | To let SSPs disclose all the entities (publishers and intermediaries) allowed to sell ad inventory through their systems |
| Format | Plain text: .txt | Structured format: .json |
| Where it lives | publisher.com/ads.txt | ssp.com/sellers.json |
| Seller relationship | Direct or reseller | Publisher, intermediary or both |
DSPs are the ones who ask for these files, and when they have them, they match the seller IDs in the publisher’s ads.txt with the entries in each platform’s sellers.json. When both files agree, the buyer can trust the path.
Together with the SupplyChain object, these files show every company involved in an ad transaction This helps fight digital fraud by increasing traceability and trust between the different players in the market.
Why does sellers.json matter for publishers?
Even though sellers.json is a buyer’s tool, publishers can feel its impact in their revenue.
- Buyers verify before they bid. They look at both files, sellers.json and ads.txt, and compare them to make sure the data matches. If it doesn’t, they may skip the publisher’s inventory.
- Mismatches look like fraud. A seller listed in one file but missing from the other can be flagged as unauthorized. That traffic often loses bids or gets blocked.
- Transparency attracts better demand. More transparency means more trust from DSPs and eventually more demand.
- It supports supply path optimization (SPO). Buyers use sellers.json to find the shortest and most efficient paths to inventory. Fewer intermediaries mean less spend lost to fees, so publishers keep a bigger share of ad revenue.
In other words, an outdated or incorrect entry can cost the publisher money without them noticing.
Your next step toward a cleaner supply chain
Now you know that sellers.json and ads.txt work together to make AdTech relationships more transparent. You also know that a small mistake in either file can cost you bids without you noticing. Don’t let simple errors cost you revenue. Contact Refinery89 and let’s check your setup together.
