Glossary/Programmatic/Second-price auction
What is a second-price auction in programmatic advertising?
How second-price auctions work, why most of programmatic moved to first-price auctions, and what that means for floors and bid shading.
Written by Samhub with the help of AI·Updated 13 Oct 2026·3 min readIn a second-price auction, the highest bidder wins but pays just above the second-highest bid, usually one cent more, instead of its own bid.
An example
| Bidder | Bid | Result |
|---|---|---|
| A | €3.00 | Wins, pays €2.21 |
| B | €2.20 | Second highest |
| C | €1.50 | Loses |
Illustrative numbers. In a first-price auction, A would pay its full €3.00.
Why programmatic moved to first-price
With header bidding, several auctions run before the final one, and second-price rules became hard to follow and easy to game. Around 2017 to 2019 most exchanges switched to first-price auctions, where the winner pays its own bid.
16 pages for publishers, with a checklist for data, programmatic and direct sales.
What it means for publishers
Floors work differently
Soft floors mattered in second-price. Hard floors matter most now.
Buyers shade bids
DSPs lower their bids to avoid overpaying in first-price auctions.
Data still sets the price
Buyers bid more when they can see who the impression reaches.
CPM uplift at Stampen Media after activating first-party audiences with Samhub.
Frequently asked questions
Rarely in display programmatic today. Some platforms and search auctions still use variations of it.
A way for buyers to lower bids in first-price auctions, so they do not pay much more than needed.
First-price is more transparent. Publishers protect value with floors and audience data.
A floor below which a bid can still win, at a lower price. It mattered mostly in second-price setups.
Related terms
The winner pays exactly what it bid.
The lowest price a publisher accepts for an impression.
An auction for every single impression.
Lets many buyers bid at once before the ad server decides.
Lowering bids to avoid overpaying in first-price auctions.
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.
