Glossary/Programmatic/Demand-side platform (DSP)
What is a DSP (demand-side platform) in advertising?
What a demand-side platform does, how it buys impressions in real time, and what publishers need to do so DSPs can find and value their audiences.
Written by Samhub with the help of AI·Updated 13 Oct 2026·3 min readA demand-side platform (DSP) is software that advertisers and agencies use to buy ad impressions from many publishers at once. It evaluates each impression and decides in real time whether to bid and how much.
How a DSP works
The buyer sets up a campaign
Budget, target audience, formats, price limits and any deal IDs.
Bid requests arrive
Ad exchanges and SSPs send the DSP a bid request for each available impression.
The DSP evaluates the impression
It checks the site, ad size, device and any audience data against the campaign.
It bids or passes
If the impression fits, the DSP bids. The winning ad is shown within a fraction of a second.
Well-known DSPs
The largest include The Trade Desk, Google Display & Video 360 and Amazon DSP. Many markets also have regional DSPs that are popular with local agencies.
Why DSPs matter to publishers
Most programmatic money reaches you through a DSP. The DSP can only value what it can see. If your impressions arrive without audience signals, the buyer bids as if your reader could be anyone, and your inventory competes on price alone.
16 pages for publishers, with a checklist for data, programmatic and direct sales.
How publishers make their inventory visible to DSPs
Pass audience signals in the bid
Send privacy-safe audience segments with the impression, so buyers can target them.
Package audiences as deals
Give buyers a deal ID for each audience they want, in a private marketplace.
Be consistent across SSPs
Use the same audience names in every SSP, so a buyer finds the same audience everywhere.
CPM uplift at Stampen Media after activating first-party audiences with Samhub.
Frequently asked questions
A DSP works for the buyer and decides what to bid. An SSP works for the publisher and offers the impression to many buyers to get the best price.
Not to sell. Publishers sell through SSPs and ad servers, but they need to understand DSPs because that is where their buyers set up campaigns.
A code a buyer adds to a campaign to bid in a specific private deal, such as a PMP built on a publisher’s audience.
Only what you choose to pass. Audience segments can be shared without sending personal data, for example as segment IDs.
Related terms
The software publishers use to sell impressions.
The buy side and sell side of programmatic.
An auction for every single impression.
Invite-only auctions for premium inventory.
Negotiating and booking ad space for a campaign.
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