DSP (demand-side platform)

A DSP (demand-side platform) is the software advertisers and agencies use to buy advertising automatically, from many sellers at once, through a single interface. It sits on the buyer’s side of programmatic trading.

How does it work?

A DSP connects to the sellers’ side, the SSPs, which put screen owners’ inventory up for sale. For digital out-of-home (DOOH), meaning screens in streets, malls and stations, the buyer sets up a campaign in the DSP:

• targeting rules: locations, venue types, days and hours,
• budget and pacing,
• a maximum price, usually expressed as a CPM,
• the creatives, in the formats each screen accepts.

The DSP then evaluates the available opportunities. Depending on the deal, it either bids at auction through real-time bidding, or buys at a price already agreed with a specific seller (private or guaranteed deals).

One DOOH-specific twist: a play is not one viewer. The DSP relies on an audience estimate per play to turn a CPM into a price per play. The source of those estimates is therefore part of the deal, whether anyone says so or not.

Example

Illustrative example: an agency gives its DSP a budget of €5,000, a maximum CPM of €10, and a target of screens near train stations on weekday mornings. The DSP finds eligible plays across several networks. A play estimated at 20 viewers costs at most €0.20 at that CPM. Over the campaign, the DSP spends the budget on plays that fit the rules, for at least 500,000 estimated impressions.

Why it matters when you plan a DOOH campaign

A DSP is powerful when you need scale and flexibility across many networks. It is also a layer of technology, costs and estimates between you and the screen. Before buying through one, check three things: which screen networks it actually reaches in your area, whose audience figures it uses to price each play, and whether your slots are guaranteed or only won at auction.

For a campaign that depends on presence on specific local screens, those answers matter more than the interface. Some local networks are not connected to any DSP, so a DSP-only plan can miss the screens closest to your customers.