Programmatic
Bid request
A bid request is the message an SSP or exchange sends to potential buyers describing an available ad impression, inviting them to bid on it in a real-time auction.
A bid request is the "item for sale" notice in real-time bidding. It is usually a JSON message following OpenRTB and contains an auction ID, the impression details (size, format, position, floor), the site or app (domain or bundle ID, content categories), the device (user agent, operating system, IP-derived location), available user identifiers and consent signals such as a IAB TCF Consent string, plus the supplyChain object showing who is selling.
Buyers' DSPs read this in milliseconds and decide whether to answer with a bid response. A single page view can create dozens of bid requests, because each SSP and reseller may forward the same opportunity to many bidders (bid duplication).
Everything in a bid request is claimed by the seller, not proven. Fraudsters forge bid requests to fake premium domains (domain spoofing), apps or CTV devices. That is why buyers cross-check them against ads.txt, sellers.json and schain, and run pre-bid filtering. The data in bid requests, collectively the bidstream, is also at the heart of privacy debates.
Think of it like this
A bid request is like the lot description in an auction catalogue: it tells bidders what is on offer, but a smart bidder still checks the item is genuine.
An example
{"id":"a1b2","imp":[{"banner":{"w":300,"h":250},"bidfloor":0.8}],"site":{"domain":"news.example"},"device":{"os":"Android","geo":{"country":"IND"}}}
Related terms
Bid response
A bid response is a buyer's reply to a bid request, containing its offered price and the ad (or a link to it) to show if it wins.
OpenRTB
OpenRTB is the open technical standard, maintained by IAB Tech Lab, that defines how bid requests and bid responses are formatted and exchanged in real-time bidding.
Real-time bidding (RTB)
Real-time bidding (RTB) is an automated auction in which advertisers bid on a single ad impression in the fraction of a second while a web page, app or stream is loading.
Bidstream
The bidstream is the continuous flow of bid requests and responses exchanged in real-time bidding, and the data they carry about sites, apps, devices, locations and users.
SupplyChain object (schain)
The SupplyChain object (schain) is a field in OpenRTB bid requests that lists, in order, every seller or intermediary that handled the impression on its way from the publisher to the buyer.
Sources: IAB Tech Lab: OpenRTB