What is Prebid Server?
Prebid Server is the open-source server-side header bidding engine from Prebid.org, with separate Go and Java implementations. It accepts an OpenRTB bid request, splits it into one request per configured bidder, calls them in parallel, and returns the combined bids. Prebid.js, the Prebid Mobile SDKs, AMP pages, and long-form video integrations use it to move auctions off the device.
Also called: PBS, Prebid Server Go, Prebid Server Java, PBS-Go, PBS-Java.
How it works
Its main auction endpoint takes OpenRTB 2.x JSON with Prebid-specific settings in ext.prebid and per-bidder parameters under imp.ext.prebid.bidder. Stored requests let a publisher keep most of the request on the server and send only an ID plus what changed. Prebid Server then applies privacy rules, enriches the request, and sends each bidder adapter a request in the format that bidder expects.
Because it speaks OpenRTB on both sides, Prebid Server is one of the largest sources of OpenRTB traffic. The request a bidder receives from it is not what the page sent: each bidder gets only its own parameters under imp.ext, other bidders' settings are removed, and modules can add or reshape fields. Debugging a bid request therefore needs the request as Prebid Server sent it, not the one the browser made.
Operators set their own timeouts, and the BidRequest.tmax forwarded to bidders can be lower than the overall auction budget, since the server needs time to merge results. Each adapter also declares the media types and features it supports, so a field present in the incoming request may never reach a bidder whose adapter does not handle it.
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Related terms
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