Bid Request

A bid request is the packet of information that opens a real-time bidding (RTB) auction for a single ad impression. When a person loads a web page or an app screen with a programmatic ad slot, the publisher's supply-side platform (SSP) instantly assembles a message and broadcasts it to the demand-side platforms (DSPs) that buy ads on advertisers' behalf. That message is the bid request. It describes what is for sale in enough detail for buyers to decide whether they want it and how much it is worth to them. The OpenRTB specification, maintained by the industry body IAB Tech Lab, standardizes the shape of that message so an SSP and a DSP built by different companies can still speak the same language and trade in the roughly hundred milliseconds a page takes to render.

The contents of a bid request are what make targeting possible. A typical request carries the ad slot's size and format, the page or app it will appear on, the device and operating system, coarse geography, and whatever audience signals are permitted — a hashed identifier, contextual tags, or, increasingly, privacy-preserving signals rather than a raw cookie. Buyers read those fields, match them against their campaigns, and return a bid price with the creative they want to show. The highest eligible bid wins, the winning ad is served, and the reader sees it — all before the page finishes loading. So the bid request is not a small technical detail; it is the moment where publisher supply meets advertiser demand, and its quality shapes how well the whole trade works.

It helps to keep three closely linked terms straight. The bid request is the outbound invitation the SSP sends to buyers. The bid response is what each DSP sends back — a price, a creative, and the terms it is willing to buy on. The impression is the actual served ad that results when a bid wins and the ad renders on the screen. So the request asks, the response answers, and the impression is the outcome. One page load can generate many bid requests (one per slot, sometimes duplicated across exchanges) and many bid responses, but only one winning response per slot becomes an impression. Confusing the request with the impression leads to bad counting, because a request is merely an opportunity offered, not an ad anyone saw.

A bid request also differs from the query that drives paid search. In search, an advertiser bids to appear against a keyword a person typed, and the auction is tied to intent expressed in the query. A programmatic display or video bid request is tied to a specific impression on a specific screen for a specific user context, decided in real time by machines rather than by a typed keyword. Both are auctions, but the unit being sold and the signal being read are different. The bid request belongs to the display, video, native, and connected-TV world of impression-by-impression trading, where each opportunity is described, offered, and settled on its own, thousands of times a second across the open programmatic ecosystem.

For a publisher, the practical work is making bid requests worth bidding on. That means passing accurate, complete, and honest information — real page context, correct ad sizes, valid formats, and clean supply-path detail — so buyers trust the request and pay more for it. Padding requests with misleading data, or letting the same impression be offered through so many resellers that buyers cannot tell what they are buying, erodes trust and depresses prices. Supply-path optimization, where buyers deliberately favor short, transparent routes to inventory, is a direct response to messy request practices. A clean, well-described bid request is simply a better product, and it earns better bids.

For a buyer, the discipline is reading bid requests critically rather than bidding on volume. That means filtering out requests that carry weak or suspicious signals, watching for invalid traffic hiding behind plausible-looking fields, and valuing genuine context and transparency over sheer request count. The failures on both sides are the same in shape — treating the bid request as a rubber stamp rather than a described offer. A publisher that inflates requests and a buyer that bids on everything both end up in a market where prices reflect noise, not value. Treating the bid request as the meaningful, informative unit it is keeps programmatic trading efficient and honest.

Bid request — the real-time invitation an SSP broadcasts to buyers for a single ad impression — is the message that opens a programmatic auction under the OpenRTB standard.

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