Glossary/Programmatic/Prebid
What is Prebid? The open-source header bidding tool explained
What Prebid is, how Prebid.js and Prebid Server differ, and how publishers get more revenue from it.
Written by Samhub with the help of AI·Updated 13 Oct 2026·3 min readPrebid is open-source software for header bidding. It lets many SSPs bid on an impression at the same time before the ad server picks the winner. It is maintained by Prebid.org.
Prebid.js vs Prebid Server
| Prebid.js | Prebid Server | |
|---|---|---|
| Runs in | The reader’s browser | A server |
| Page speed | Can slow pages with many bidders | Lighter on the page |
| Common use | Web | Apps, video, AMP and large setups |
How it works
Page loads
Prebid sends bid requests to the chosen SSPs.
Bids come back
Within a set timeout.
Ad server decides
The best bid competes with direct campaigns.
16 pages for publishers, with a checklist for data, programmatic and direct sales.
Pass audience data in the bid request
Prebid can pass first-party audience signals to bidders. Buyers bid more for impressions they can understand, so audience signals in Prebid are one of the simplest ways to raise programmatic prices.
CPM uplift at Stampen Media after activating first-party audiences with Samhub.
Frequently asked questions
The software is free. You still need someone to set it up and maintain it.
Enough for competition. Too many slow the page without raising revenue.
Often around one second. Test what works for your site.
Prebid is the most widely used tool for header bidding.
Related terms
Lets many buyers bid at once before the ad server decides.
The software publishers use to sell impressions.
An auction for every single impression.
The winner pays exactly what it bid.
Samhub audiences let you set higher floors and win more data deals, in every channel you sell.
- A walkthrough with your own data
- Built for publishers and media houses
- 30 minutes, no commitment
Turn your audience data into more revenue
Get the Media Monetization Playbook: how media houses turn first-party data into higher CPMs, data deals and direct sales. With checklists for every step.
