OpenRTB

OpenRTB is the open, industry-standard protocol that defines how bid requests and bid responses are structured in programmatic auctions, letting any supply platform and any buying platform communicate without custom integrations. Maintained under the IAB Tech Lab, it is the common language of the real-time bidding ecosystem.

How it works#

When an impression is offered for sale, the supply side sends a JSON bid request shaped to the OpenRTB specification. That request carries standardized fields, the impression details, device and user signals, the site or app, floor price, and supply-chain provenance. Buyers parse it, decide whether and how much to bid, and reply with an OpenRTB bid response. Because every participant follows the same schema, an Ad Exchange can broadcast one request to many buyers and compare their answers directly.

Why it matters#

Before OpenRTB, each exchange and bidder pair needed bespoke integration work. The protocol turned that into plug-and-play interoperability, which is what allowed Real-Time Bidding (RTB) to scale across the whole industry. Later versions added fields that improve transparency and fraud resistance, most notably the SupplyChain Object (schain), which records every intermediary that touched an impression on its way to the buyer.

For anyone analyzing how an ad reached a page, OpenRTB fields are the raw record of the transaction underlying Programmatic Advertising.

Related terms: Real-Time Bidding (RTB), SupplyChain Object (schain), and Programmatic Advertising.