Prebid
Prebid is a family of open-source header bidding tools that lets publishers run auctions across multiple demand partners before calling their ad server. It includes Prebid.js for websites, Prebid Server for server-side auctions and Prebid Mobile for apps, maintained by the independent Prebid.org organisation.
What is Prebid?
Prebid is the most widely used open-source implementation of Header bidding. Maintained by Prebid.org, an independent organisation supported by publishers and adtech companies, it provides a library of bidder adapters, modules for identity, floors and consent, and server-side options. Publishers configure which SSP and bidder partners participate, set timeouts and floor rules, and pass results to their ad server. Because the code is open, publishers can inspect how auctions run, which supports transparency compared with closed wrappers.
How Prebid works
On a web page, the Prebid.js wrapper sends bid requests to configured bidder adapters at the same time and waits for responses until a timeout. The winning bids are passed to the publisher’s ad server as key-values, where they compete with direct and other demand. Prebid Server performs similar auctions on a server to reduce browser and app load.
- The publisher configures Prebid with ad units, bidder adapters, timeouts and modules.
- When a page or app loads, Prebid sends bid requests to all configured bidders in parallel.
- Bids returned before the timeout are collected and compared.
- Winning bid details are sent to the ad server as key-values to compete with other demand.
- If the Prebid bid wins in the ad server, its creative is rendered.
Why it matters
Prebid gives publishers a transparent, vendor-neutral way to run header bidding without depending on a single company’s wrapper. It has become a widely used standard framework for connecting many SSPs and bidders.
For publishers
Prebid lets publishers add or remove demand partners flexibly and see exactly how their header auction works.
For adtech platforms
SSPs and bidders build and maintain Prebid adapters to access publisher inventory through the framework.
Practical example
A regional news site uses Prebid.js with five bidder adapters and Prebid Server for its app, then passes the highest bids into its ad server for final selection.
Key considerations
- Each additional bidder adds latency in client-side setups, so timeouts and partner count need tuning.
- Prebid requires technical resources to configure, update and monitor.
- Server-side auctions reduce page load but can limit cookie matching for some bidders.
More Publisher Monetization terms
Frequently asked questions
Is Prebid free to use?
Yes. Prebid is open source, though publishers bear the cost of implementing and maintaining it and of hosting Prebid Server if they run their own.
What is the difference between Prebid.js and Prebid Server?
Prebid.js runs auctions in the browser, while Prebid Server runs them on a server, reducing load on the user’s device.
Does Prebid work for apps and CTV?
Yes. Prebid Mobile SDKs and Prebid Server support in-app inventory, and Prebid Server can be used for some video and CTV setups.