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DSP vs SSP: what does each do?

Reviewed by Visprisca Ad Tech Engineering Team•Last updated: October 2026
Direct Answer

A DSP (Demand-Side Platform) works for ad buyers, optimizing bids and media buying across millions of publisher impressions. An SSP (Supply-Side Platform) works for publishers, aggregating ad inventory, managing price floors, and maximizing revenue by connecting inventory to multiple DSPs through real-time auctions.

Detailed Explanation

DSPs and SSPs represent the two complementary sides of the programmatic marketplace. Think of the ad market like a stock exchange: the DSP is the brokerage software used by traders (advertisers) to buy shares at the best possible price, while the SSP is the listing platform used by companies (publishers) to sell their shares.

The DSP focuses on buyer ROI: calculating conversion probabilities, finding target audiences, applying bid shading, and enforcing campaign budgets.

The SSP focuses on publisher yield: enforcing price floors, filtering out unwanted ad categories (brand safety for publishers), and ensuring maximum fill rate across competing demand sources.

Technical Definition: Supply Path Optimization (SPO)

The practice by DSPs and advertisers of finding the most direct, cost-efficient, and transparent route to purchase a publisher's ad inventory.

Illustrative Worked Example*Clearly labeled illustrative per Accuracy Rule

How DSP and SSP Interact in an OpenRTB Auction

An advertiser wants to reach in-app gamers in North America.

›1. SSP Role: Aggregates ad slots across 50 gaming apps, sets a minimum floor of $1.50 CPM, and broadcasts an OpenRTB 2.5 request.
›2. DSP Role: Ingests the bid request, matches targeting criteria, estimates a 3.5% install rate, and submits a $2.40 CPM bid.
›3. SSP Role: Verifies the bid exceeds the $1.50 floor, selects the DSP as the auction winner, and delivers the creative.
›4. Win Notification: SSP sends an nurl/burl win ping to the DSP to confirm ad rendering.

Both platforms operate in synchronization within a strict 100ms protocol window.

What to Do Next

  • 1Publishers: review which SSPs have direct OpenRTB connections to performance DSPs like Visprisca.
  • 2Advertisers: verify that your DSP minimizes intermediary resellers to reduce unnecessary SSP tech fees.
  • 3Audit your sellers.json records to ensure direct publisher relationships are correctly labeled.

Related Questions

How does programmatic monetization work?What are ads.txt, app-ads.txt and sellers.json?How does Visprisca connect to an exchange (OpenRTB basics)?
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