Glossary/Programmatic/Real-time bidding (RTB)
What is real-time bidding (RTB) and how does it work?
How real-time bidding sells a single ad impression in a fraction of a second, what is inside a bid request, and what decides the price a publisher gets.
Written by Samhub with the help of AI·Updated 13 Oct 2026·4 min readReal-time bidding (RTB) is a way of selling ad impressions one at a time, in an automated auction that runs while the page loads. Buyers bid for each impression, and the highest bid wins.
How real-time bidding works
A reader opens a page
The page has an ad slot that needs an ad.
A bid request goes out
The publisher’s SSP or header bidding wrapper sends a bid request to many buyers at once.
Buyers evaluate and bid
Each DSP decides whether the impression fits a campaign and how much it is worth.
The winner is shown
The highest bid above the floor price wins and the ad is displayed, usually well under a second after the page started loading.
What is in a bid request
Most bid requests follow OpenRTB, an open standard from the IAB Tech Lab. It means buyers and sellers describe impressions the same way, so any DSP can bid on any SSP.
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What decides the price
| Factor | Why it matters |
|---|---|
| Audience signals | Buyers pay more when they can see who the impression reaches. |
| Viewability | Ads that are likely to be seen are worth more. |
| Competition | More bidders in the auction push the price up. |
| Floor price | Sets the minimum the publisher accepts. |
| Auction type | Most exchanges now run first-price auctions, where the winner pays its own bid. |
RTB and first-party data
As third-party cookies disappear, many bid requests arrive with little information about the reader. Publishers who pass their own audience data in the bid give buyers a reason to bid higher.
CPM uplift at Stampen Media after activating first-party audiences with Samhub.
Frequently asked questions
RTB is one part of programmatic. Programmatic also includes fixed-price deals such as programmatic guaranteed, which are bought automatically but not auctioned.
The whole auction usually happens in a fraction of a second, while the page loads.
An open standard from the IAB Tech Lab that defines how bid requests and bids are formatted, so all platforms can talk to each other.
Bid requests can contain IDs and location, so RTB falls under GDPR. Consent is passed with the request, usually through the IAB TCF.
Related terms
The software advertisers use to buy impressions.
The software publishers use to sell impressions.
Lets many buyers bid at once before the ad server decides.
The lowest price a publisher accepts for an impression.
The buy side and sell side of programmatic.
Open-source header bidding software.
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