A publisher technique that offers each impression to many exchanges simultaneously before the page's ad server makes its decision, rather than sequentially in a Waterfall. Header bidding raised publisher yield and gave buyers access to more inventory, at the cost of page latency and duplicated bid requests, which is the origin of Supply Path Optimization. Prebid.js is the dominant open-source implementation.
Cite this entry:
Agency Echelon. "Header Bidding." Agency Echelon Reference, reviewed September 2026. https://agencyechelon.com/reference/glossary/header-bidding/