bidderid

BidderID, or bidder id, is a unique identifier assigned to a bidder participating in programmatic advertising auctions, particularly in real-time bidding (RTB) environments. It serves to distinguish one bidder from another during an auction and to support reporting, auditing, and optimization. In practice, a bidder ID is issued by an exchange, supply-side platform (SSP), or demand-side platform (DSP) and is used within bid requests and responses to attribute bids to the correct bidder. The identifier may be stable over time for a given bidder, or it may rotate per campaign or per auction depending on the implementation. It is typically transmitted as part of the auction protocol payload, but the exact field name and format vary across protocols and platforms; it may be hashed or opaque to publishers.

Within a header bidding or OpenRTB workflow, the bidderID helps the exchange or mediation layer route bids to the correct bidder and aggregate performance statistics such as bid rate, win rate, and revenue by bidder. It is not a user identifier and is usually separate from cookies or device identifiers, though it may be linked to a bidder's account to facilitate account-level reporting.

Privacy and regulatory considerations apply: some bidding data can reveal bidding strategies, and stores of bidder IDs are subject to data protection rules and consent regimes. See also Real-Time Bidding, OpenRTB, DSP, SSP, header bidding, and ad tech privacy practices.