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DSPs & SSPs: What They Are (and How They Work in Programmatic Ads)

“DSP” and “SSP” are the backbone of how ads get from brands (advertisers) to websites/apps (publishers) in the programmatic world. And understanding them is the first step to running (or monetizing) successful programmatic campaigns.

This beginner’s guide demystifies DSPs and SSPs: what they do, how they work together, and why they matter for anyone getting started in programmatic.

A Simple Analogy to Explain DSPs & SSPs

Let’s start with something familiar: online shopping.

  • Imagine you’re a brand (advertiser) looking to buy ad space, like a shopper searching for the perfect product (relevant ad inventory).
  • A publisher (e.g., a news website or mobile app) has ad space to sell, like a store with products on shelves.

In this scenario:

  • A DSP (Demand-Side Platform) is your “shopping app” (think Amazon): It lets you browse, compare, and buy ad space from hundreds of publishers in one place, all with automation.
  • An SSP (Supply-Side Platform) is the store’s “inventory manager”: It helps publishers organize their ad space, set prices, and sell it to the highest bidder (via advertisers on DSPs).

Together, they make programmatic advertising fast, efficient, and targeted, no manual phone calls or spreadsheets required.

What Is a DSP (Demand-Side Platform)?

For Advertisers: Your “One-Stop Shop” for Buying Ad Space

A DSP is a technology platform that lets advertisers (brands, agencies, or marketers) buy digital ad space (inventory) from publishers—programmatically, in real time. Instead of negotiating directly with individual websites or apps, you use a DSP to access thousands of inventory sources at once.

How a DSP Works

1. Set Your Goals & Budget:

You tell the DSP what you want to achieve (e.g., “reach 100,000 fitness fans” or “drive 500 app installs”) and how much you’re willing to spend.

2. Target Your Audience:

Use the DSP’s tools to narrow down who sees your ads, by demographics (age, location), interests (e.g., “yoga enthusiasts”), behavior (e.g., “visited my website”), or even device (mobile vs. desktop).

3. Bid on Ad Space:

When a user visits a publisher’s site/app, the DSP automatically bids on the available ad spot (in milliseconds!), competing with other advertisers. This is called “real-time bidding (RTB).”

4. Track & Optimize:

The DSP shows you how your ads perform (e.g., clicks, conversions) and lets you tweak your campaign, like increasing bids for high-performing audiences or pausing underperforming ad spots.

Example: How an Advertiser Uses a DSP

A fitness brand wants to promote its new workout app. Instead of emailing 50 fitness blogs to buy ad space, it uses a DSP to:

  • Target users who follow fitness influencers or search for “home workouts.”
  • Bid on ad spots in fitness apps and blogs.
  • Only pay when someone clicks the ad (CPC) or installs the app (CPI).
  • Adjust bids to spend more on audiences that actually install the app (e.g., 25–34-year-olds in urban areas).

What Is an SSP (Supply-Side Platform)?

For Publishers: Your “Sales Tool” for Monetizing Ad Space

An SSP is a technology platform that lets publishers (websites, apps, or content creators) manage, price, and sell their ad space to advertisers, again, programmatically and in real time. It’s how publishers turn their traffic into revenue without doing manual sales work.

How an SSP Works

1. List Your Ad Space:

You tell the SSP what ad spots you have (e.g., “homepage banner” or “in-app interstitial”) and set minimum prices (e.g., “$2 CPM for the banner”).

2. Connect to Buyers:

The SSP links your ad space to hundreds of DSPs (where advertisers are buying). This means your inventory is visible to far more potential buyers than you could reach alone.

3. Run Auctions:

When a user visits your site/app, the SSP holds a real-time auction for your ad spot. Advertisers on DSPs bid for the space, and the highest bidder’s ad gets displayed.

4. Maximize Revenue:

The SSP optimizes which ads run to get you the highest possible price.

Example: How a Publisher Uses an SSP

A fitness blog with 50,000 monthly readers wants to monetize its traffic. Instead of hiring a sales team, it uses an SSP to:

  • List its homepage banner, sidebar ad, and in-article spots.
  • Set a minimum $1.80 CPM for the homepage banner.
  • Let the SSP run auctions so fitness brands (via DSPs) bid on the space.
  • Earn more by automatically choosing the highest bid each time a user visits.

How DSPs & SSPs Work Together (The “Programmatic Loop”)

DSPs and SSPs don’t work in silos; they’re two sides of the same coin. Here’s how they collaborate to serve an ad in less than a second:

  1. A user opens a publisher’s app (e.g., a fitness app).
  2. The publisher’s SSP notices the available ad spot and sends a “request” to all connected DSPs: “Who wants to bid on this ad spot for a user interested in fitness?”
  3. Advertisers’ DSPs receive the request, check if the user matches their target audience (e.g., “25–34-year-old fitness fans”), and submit a bid (e.g., $2.50 CPM).
  4. The SSP picks the highest bid (say, $2.50 from a workout gear brand) and tells the DSP to send the ad.
  5. The ad loads in the publisher’s app, and the user sees it.
  6. The DSP bills the advertiser, the SSP pays the publisher (minus a small fee), and both platforms track the ad’s performance (clicks, views).

This entire process takes 50–200 milliseconds—faster than the blink of an eye. No human intervention needed.

Why DSPs & SSPs Matter

For Advertisers (Why DSPs Help)

  • Save Time: No more negotiating with dozens of publishers. A DSP lets you buy ad space from thousands of sources in one place.
  • Target Better: You don’t waste money on irrelevant users. DSPs let you target people who are actually interested in your brand.
  • Control Costs: You set your budget and only pay for results (e.g., clicks, conversions).

For Publishers (Why SSPs Help)

  • Earn More: SSPs run auctions to get the highest bid for your ad space, so you make more than you would with fixed-price deals.
  • Reach More Buyers: Your ad space is visible to hundreds of advertisers (via DSPs), not just the ones you know.
  • Save Resources: No need for a sales team to pitch ad space. The SSP handles selling and billing automatically.

Common Myths About DSPs & SSPs

Let’s clear up a few misconceptions that trip up beginners:

1. Myth: “Only big brands need DSPs.”

Truth: Small and mid-sized businesses (SMBs) benefit most; DSPs let them compete with big brands for ad space at affordable prices.

2. Myth: “SSPs are only for large publishers.”

Truth: Even small blogs or apps can use SSPs. Many platforms have no minimum traffic requirements.

3. Myth: “DSPs and SSPs are the same thing.”

Truth: DSPs are for buying ad space (advertisers), SSPs are for selling ad space (publishers). They work together but serve opposite roles.

How GatherStar Fits Into the DSP/SSP Ecosystem

GatherStar bridges the gap between DSPs and SSPs, making programmatic easy for both advertisers and publishers:

  • For advertisers: Our platform integrates with top DSPs to give you access to verified publishers and 12B+ monthly ad impressions. You can target high-intent audiences, run real-time bids, and track post-click/post-view conversions...all in one dashboard.
  • For publishers: We connect your ad space to our network of advertisers to maximize your revenue. Our SSP tools let you set prices, filter irrelevant ads, and get fast payments.

Final Thought

DSPs and SSPs may sound complex, but their core purpose is simple:

  • DSP = Help advertisers buy ad space efficiently.
  • SSP = Help publishers sell ad space for more money.

With platforms like GatherStar, you don’t need to master every detail, just focus on your goals (reach, conversions, revenue) and let the technology do the rest.

Ready to get started? Whether you’re an advertiser looking to launch your first programmatic campaign or a publisher wanting to monetize traffic, GatherStar’s team is here to help.


If you’re looking to craft more effective, AI-driven ad experiences, start with GatherStar today. And if you want dedicated expert support to maximize your results, reach out to the GatherStar team to explore how we can help elevate your programmatic campaigns.