Glossary
What is Header bidding?
Also called: HB
Header bidding asks many demand partners for bids at the same time, before the ad server decides, so they all compete on price.
हिंदी में पढ़ेंWith header bidding, code on the page, or a server, calls demand partners such as SSPs and exchanges for bids before the ad server is called. The ad server then considers those bids alongside its other demand and usually makes the final decision.
It replaced the waterfall, where partners were asked one at a time in a fixed order based on past averages. In a waterfall, the first partner to meet its floor takes the impression, even if a partner further down would have paid more. Header bidding asks everyone at once, so today’s highest bidder can win.
A widely used open-source framework is Prebid: Prebid.js runs the auction in the browser, and Prebid Server runs it server to server. A timeout caps how long the page waits for bids, and winning bids reach Google Ad Manager as key-values matched to line items. Each extra bidder adds competition but also requests and waiting, so more is not always better.
Example
In a waterfall, partner A takes an impression at $2.10, though partner C would have paid $3.00. With header bidding, A bids $2.10, B $1.60 and C $3.00 at the same moment, so C wins: $0.90 more CPM for the same impression.
Why it matters to publishers
Header bidding lets real-time prices decide who wins, but each bidder adds latency, so the setup needs regular tuning.