What is sellers.json for CTV?

Overview

Sellers.json is a technical specification developed by the Interactive Advertising Bureau (IAB) Tech Lab specifically for the connected TV (CTV) advertising ecosystem. Launched in 2020 as an extension of the original ads.txt (Authorized Digital Sellers) standard, it addresses the unique challenges of CTV environments where traditional web-based verification methods fall short. The initiative emerged in response to growing concerns about CTV ad fraud, which increased by 69% between 2020 and 2022 according to Pixalate reports. Unlike desktop or mobile advertising, CTV involves complex supply chains with multiple intermediaries, making it difficult for buyers to verify legitimate inventory sources. The standard was created through collaboration between major industry players including Google, Magnite, and PubMatic, with version 1.0 finalized in June 2020. It builds upon earlier transparency efforts but adds CTV-specific fields and requirements to handle the particular characteristics of streaming television environments.

How It Works

The sellers.json file operates as a publicly accessible JSON document hosted at a standard location on a publisher's domain (typically example.com/sellers.json). Each entry in the file represents an authorized seller and includes mandatory fields: seller_id (a unique identifier), name (the business name), and seller_type (specifying whether it's a publisher, intermediary, or reseller). For CTV specifically, additional fields help identify the nature of the inventory, such as whether it's from a streaming app, set-top box, or smart TV platform. The system uses a hierarchical structure where publishers list their direct sellers, and those sellers can further list their own authorized resellers. When an ad request comes through a CTV device, buyers can cross-reference the seller ID against the published sellers.json file to verify legitimacy. The verification process happens in real-time through programmatic platforms, with most demand-side platforms (DSPs) automatically checking sellers.json files before bidding on CTV inventory. Publishers must update their files regularly (at least weekly) to maintain accuracy, and the IAB provides validation tools to ensure proper formatting.

Why It Matters

Sellers.json matters because CTV advertising represents one of digital marketing's fastest-growing segments, projected to reach $25 billion in the US alone by 2024. Without proper verification, this growth attracts sophisticated fraud schemes including CTV-specific threats like app spoofing and device hijacking. The implementation of sellers.json has helped reduce invalid traffic in CTV campaigns by approximately 40% according to 2022 industry studies. For advertisers, it provides confidence that their CTV budgets reach legitimate viewers rather than fraudulent impressions. For publishers, it establishes credibility in the marketplace and can increase fill rates by 15-25% for verified inventory. The standard also supports regulatory compliance with emerging privacy laws by creating auditable supply chains. As CTV continues to merge with traditional television advertising, sellers.json serves as a critical bridge between digital transparency standards and broadcast media buying practices.