Vistar Media Blog

What is a Demand-Side Platform (DSP)?

Written by Hannah Lyder | May 24, 2023

Today’s marketers are managing more moving parts than ever before, from audience data to creative decisions. You’re connecting with people across search, social, TV and digital and out-of-home, all while proving the value of every impression. Amid that complexity, one tool helps ease planning and campaign execution: a demand-side platform (DSP).

Understanding DSPs isn’t just for media buyers anymore. Brand managers, strategists and marketing leads are expected to speak confidently about how these systems work — especially when discussing the details that matter. Let’s explore what a DSP does, why it matters and how it simplifies advertising in an increasingly automated world.

The definition of a demand-side platform

A DSP is software that lets advertisers buy and manage ad inventory automatically, all from one place. While many DSPs support various types of digital media, digital out-of-home (DOOH) DSPs are specialized platforms built specifically for buying and managing digital out-of-home inventory.

In short, a DSP is the control center for modern advertising, helping marketers evaluate multiple campaign variables to decide what to buy, at what price and where to show it. 

Instead of reaching out to every website, app or digital media owner individually, marketers use a DSP to access that inventory programmatically, triggering real-time ad placements through data-driven automation. Without it, media buying is more fragmented. 

While DSPs don’t eliminate complexity altogether, they remove a lot of the guesswork. With thousands of audience segments, contextual options and real-time performance data available, media planning and monitoring become more precise — and a lot easier to manage — within a DSP platform. 

How a DSP works: Simplifying a complex process

Behind every automated ad placement is a balance between buyers and sellers. That’s where DSPs and SSPs come together to make programmatic advertising possible.

DSP vs. SSP: Two sides of the same coin

You’ll often hear the term supply-side platform (SSP) mentioned alongside DSP. They’re complementary systems that power the programmatic marketplace.

  • A DSP is used by marketers and advertisers — the demand side — to buy ad impressions.
  • An SSP is used by media owners — the supply side — to sell available ad inventory at the best possible price. The ad server is software that manages the creation, scheduling, delivery and performance tracking of ad campaigns across your network. 

Together, DSPs and SSPs automate the buying and selling process by connecting advertisers and media owners through real-time bidding on a shared exchange.

How does a DSP work?

A DSP automates the ad-buying process using real-time bidding (RTB) and other programmatic methods. Here’s what happens, in seconds:

  1. You set up your campaign. You begin by defining your goals, audience and targeting parameters, such as specific buyer personas, locations, times of day or contextual triggers. The DSP then uses this information to identify and bid on ad placements that align with your strategy.
  2. An ad exchange signals the auction. Media owners make their inventory available through an exchange, and the DSP reviews that opportunity through automation — audience, location and fit.
  3. The DSP places a bid. Based on your targeting and budget, the DSP instantly determines the value of that impression and submits a bid.
  4. The winning ad appears. The highest qualified bid wins, and your creative displays to that specific audience, all in real time.

Not every DSP transaction is an auction. Private marketplace (PMP), preferred and programmatic guaranteed deals offer ways to secure premium inventory with fixed pricing or guaranteed impressions, all managed within the same platform. Choosing the best way to secure inventory for your unique situation can be complicated. Contact our team to talk through your needs. 

Why DSPs matter for advertisers and marketers

For advertisers and marketers, eliminating much of the guesswork in audience targeting and providing an easier route to campaign launches offers strategic clarity. A DSP connects the dots between performance, targeting and proof of ROI.

  • Expansive reach, centralized control: A DSP connects advertisers to a wide network of premium screen inventory, from transit hubs and retail environments to fitness centers and airports. It simplifies campaign management with centralized tools for planning, activation and performance tracking.
  • Smarter targeting and stronger efficiency: Move beyond broad demographics. DSPs use data-driven signals — location, behavior, context and even environmental triggers — to help you reach the right audience at the right time. The result: less waste, more relevance and measurable impact.
  • Real-time visibility and measurable ROI: DSP analytics give marketers immediate insights into what’s working and what’s not. You can optimize mid-campaign, allocate spend more intelligently and confidently demonstrate results to leadership.

Specialized DSPs for DOOH advertising

Not all DSPs are the same. DOOH DSPs are purpose-built for the nuances of digital out-of-home advertising, combining automation and data from digital channels with the physical impact of the real world.

These platforms offer a more tailored approach to advanced targeting — such as behavioral data, first- and third-party integrations and context-based targeting (like triggering ads by weather conditions or time of day). For example, a wellness brand could use a DOOH DSP to reach audiences in health-focused venues, delivering relevant messages that fit naturally within those environments.

When activating programmatic DOOH (pDOOH) campaigns, a DOOH-specific DSP is often a great choice. Unlike general DSPs built for online or mobile channels, DOOH DSPs are designed to handle the unique variables of out-of-home, from diversified venue types and screen formats to impression multipliers and foot traffic attribution, ensuring more accurate targeting and measurement.

DSP transaction types for buying ad space

Different campaigns call for different buying methods. DSPs typically support four key transaction types:

Open exchange

In an open exchange, advertisers bid in real time for available ad inventory across multiple publishers. This approach delivers maximum scale and cost efficiency but offers less control over placement quality or guaranteed impressions.

Private marketplace (PMP) deals

Operating by invitation only, private marketplaces give advertisers access to premium, brand-safe inventory at negotiated rates. They provide transparency, control and higher-quality placements—ideal for brands prioritizing relevance and reputation.

Preferred deals

Through preferred deals, advertisers negotiate fixed pricing and gain early access to select inventory before it enters an open auction. This model combines flexibility and predictability but doesn’t guarantee impression volume.

Programmatic guaranteed deals

With programmatic guaranteed deals, advertisers lock in a set price and reserved inventory directly with publishers. It’s the go-to choice for campaigns that demand a specific reach, certainty and total control over placement. If you’re considering a programmatic guaranteed deal, remember, unlike other transaction types your budget is committed. You won’t be able to lower your spend later since the media owner is agreeing to commit space to you.

The power of strategy and scale

Advertising has never offered so many possibilities, or so many moving parts. 

A DSP brings programmatic intelligence to channels like digital out-of-home, automating the buying process, optimizing bids in real time and refining audience delivery with every impression.

But with the right DSP, you gain the agility to plan and adjust campaigns strategically, ensuring your message reaches the right people, at the right moment, on the right screen — and you can measure the impact with confidence.

Ready to bring it all together?

See how a DSP built for advertisers and marketers can simplify your media strategy and scale your impact. Learn more about:

  • The programmatic marketplace
  • Vistar’s first truly intelligent platforms for buying and selling OOH
  • How to tell stories that delight and deliver at any scale