What is a bid request?
A bid request is the message an SSP or ad exchange sends to potential buyers announcing an available ad impression and inviting bids. It describes the opportunity, including the site or app, ad size or format, device type, approximate location, available user or household identifiers and privacy consent signals, so each buyer can decide whether to bid and how much.
Bid requests follow the OpenRTB specification and are sent in huge volumes, often millions per second across the industry. Buyers reply with a bid response containing a price, a creative reference and sometimes a Deal ID. The collective flow of requests is called the bidstream.
Bid requests are also where fraud and privacy issues surface. A fraudster can falsify the domain or app fields (domain spoofing), and data in the request can be collected by bidders who never win. That is why the supplyChain object, consent strings under the IAB TCF and IAB Global Privacy Platform, and data minimization matter.