Header bidding
A technique that lets multiple demand sources bid on a publisher’s impression at the same time, before the ad server decides.
What is header bidding?
Header bidding, sometimes called pre-bidding or advance bidding, is a programmatic setup where a publisher offers each impression to several demand partners at once before calling its primary ad server. It emerged to replace the waterfall, in which partners were asked one at a time in a fixed order, often leaving value on the table. Client-side header bidding runs in the browser using a wrapper such as Prebid.js, while server-side setups move the auction to a server to reduce page latency. The winning header bid is passed to the ad server, where it competes with direct campaigns and other demand.
How header bidding works
Code on the page or a server-side service requests bids from several partners simultaneously and passes the best into the ad server.
- As the page or app loads, the header bidding wrapper identifies the available ad slots.
- The wrapper sends bid requests to all configured demand partners in parallel.
- Partners return bids within a timeout set by the publisher.
- The highest bids are passed to the ad server as key-values.
- The ad server compares them with direct and other demand and serves the winning ad.
Why it matters
It increases competition for each impression compared with calling partners one after another.
For publishers
Simultaneous competition among partners usually raises the price paid per impression and gives better visibility into true demand.
For adtech platforms
SSPs and exchanges compete on equal terms for each impression, which rewards strong demand and efficient integrations.
Practical example
A news site runs an auction among six demand partners for every article-page slot.
Key considerations
- Too many client-side partners can slow page load and hurt user experience; timeouts must be tuned.
- Server-side bidding reduces latency but can lower cookie match rates for some partners.
- The same buyer may appear through multiple partners, increasing auction duplication.
- Wrapper configuration and floors should be reviewed regularly as partners change.
More Publisher Monetization terms
Frequently asked questions
What is a header bidding wrapper?
It is code that manages the partners, timeouts and rules for the header auction; Prebid is a widely used open-source option.
What is the difference between client-side and server-side header bidding?
Client-side runs the auction in the user’s browser; server-side runs it on a server, cutting page load but sometimes reducing data available to bidders.
Does header bidding work in apps?
Yes, through in-app bidding approaches that run a unified auction via the app’s SDK or mediation layer.