Header bidding wrapper

A header bidding wrapper is the code that runs a publisher's header bidding: it calls the chosen demand partners in parallel, enforces one timeout, collects the bids and passes them to the ad server.

Early header bidding meant one script per SSP, each with its own timer. Wrappers replaced that with a single container. Prebid.org describes its core as the header bidding wrapper itself, with bidder adapters and modules plugged in (Prebid.org, accessed 9 November 2026). The wrapper delays the ad server call for a set time and gathers bids. It then sends the winning prices to the ad server as key-values that match line items set up by ad ops (Prebid.org, Introduction to Header Bidding).

Wrappers also handle consent signals, price floors, currency conversion, user IDs and analytics. A client-side wrapper runs in the browser. A server-side wrapper, such as Prebid Server, moves the calls off the page to cut browser load, at the cost of cookie matching. Many publishers run a hybrid. The header bidding vs server-side bidding comparison covers the trade-offs.

Example: Prebid's guidance on timeouts names the balance a wrapper must strike: too short, and bidders cannot answer; too long, and revenue falls as readers leave before the ad server call (Prebid.org, Prebid timeouts). A publisher testing 1,000 ms against 1,500 ms compares revenue per page view, not bid counts.

Related terms: header bidding, Prebid.js, Prebid Server, bidder adapter, timeout, waterfall.

Authoritative source: Prebid.org, "Introduction to Header Bidding" (accessed 9 November 2026).

Read the full guide: Header bidding explained: wrappers, Prebid.js, client-side vs server-side.