sellers.json: A simple guide to transparency in programmatic advertising

What is sellers.json

Sellers.json is a transparency standard used in digital advertising. It complements the ads.txt file by listing who is allowed to sell impressions for a publisher's domain. Each publisher can publish a sellers.json file on their own domain that lists authorized sellers and their identifiers. Buyers use this data to confirm that the seller in a bid request matches a verified entity, which reduces the risk of domain spoofing and misleading inventory.

How it works

Publishers host a sellers.json file on their domain (for example, https://example.com/sellers.json). The file contains entries for each authorized seller, including a unique sellerid and the seller's domain, along with the organization name and other optional details. Demand-side platforms (DSPs) and exchanges fetch these entries and use them to verify the sellerid that appears in bid requests. When a match is found, the buyer can bid with greater confidence; when no match is found, the impression may be flagged or deprioritized.

What data is included

Each entry in a sellers.json file includes a unique seller_id, the seller's domain, and the organization name. Other optional fields may describe the seller's role (publisher, reseller, or agency) and the status of verification. The goal is to provide enough information for a buyer to confirm that the listed seller is indeed authorized to sell that inventory.

How to access or verify sellers.json

To check a publisher's sellers.json, visit the publisher's domain and append /sellers.json, for example https://publisher-domain/sellers.json. If the file is present, you can compare the seller_id and domain in bid requests to the entries in the file. Keep in mind that not all publishers have an up-to-date sellers.json, and some inventory may be sold through partners who publish their own listings.

Adoption and impact

Sellers.json is part of a broader transparency effort in programmatic advertising, alongside ads.txt and other standards. Adoption varies by market and by publisher, but major exchanges and many advertisers now rely on sellers.json as a baseline check for authenticity. When used together with ads.txt, it provides a clearer picture of who is authorized to sell a given domain's inventory.

Common questions

• Is sellers.json a replacement for ads.txt? No. It complements ads.txt by focusing on the sellers rather than the direct publishers.
• Is it required? Not universally, but adoption is growing as buyers demand more transparency.
• How can I learn more? Check with IAB Tech Lab's guidelines and your DSP or exchange documentation for specifics on integration.