What is a Supply-Side Platform (SSP)? Here’s everything you need to know

A supply-side platform, also called a sell-side platform or SSP, is technology used to help facilitate the selling of ad space on websites and apps based on impressions. It is a core part of the ad tech ecosystem, alongside demand-side platforms, agency trading desks, ad servers, and ad networks.

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In the past, buying and selling digital ads was done by human salespeople who would negotiate ad placements and price. But today, many of these transactions are done through a process called programmatic advertising, which has made the buying and selling of digital advertising cheaper, more efficient, and faster. And if this is a new term for you, now is a good time to start exploring the world of programmatic advertising. In 2021, programmatic ad spend is estimated to surpass $150 billion worldwide, according to Statista. Meanwhile, programmatic advertising continues to gain momentum around the world, with programmatic media buys making up 85% of all digital ad spending in the US and just over 80% in Europe. And, globally, programmatic media buys are predicted to make up 68% of all digital ad spending this year.

To truly understand programmatic advertising, it’s important to get to know one of its key components: A Supply Side Platform or SSP.

What is a supply side platform?

A supply-side platform (SSP) is programmatic software for publishers to facilitate sales of their advertising impressions. By connecting publishers with multiple ad exchanges, demand-side platforms, and ad networks at once, SSPs let publishers (aka suppliers) sell impressions to a greater pool of potential buyers, and allows suppliers to set the bidding range to maximize their revenue.


What is the difference between a supply side platform and a demand side platform?

A demand-side platform (DSP) is programmatic software for advertisers. A DSP helps facilitate media buying from numerous publishers through SSPs, ad exchanges, ad networks, and direct integrations. DSPs help brands and agencies (the demand side) determine which impressions to buy and at what price (the supply side). Advertisers can select audiences based on demographics and shopping and browsing signals. SSPs provide similar functionality and technology, but are used by publishers to help optimize and get the best offer for their inventory (aka maximize yield).

Learn more about the differences between supply side and demand side platforms.

How do SSPs work?

Supply-side platforms connect publishers to multiple demand sources at the same time in a programmatic marketplace. SSPs provide the technology and resources enabling publishers to aggregate, consolidate, and manage their demand sources. Publishers set brand safety guidelines, categories, and pricing. Once publishers set the criteria, the SSP holds an auction that takes all of these factors into account, and the highest bidder wins the auction.

Does Amazon have an SSP?

Yes, Amazon DSP has access to third-party publishers’ inventory via Amazon Publisher Services (APS). Through APS, Amazon offers advertisers buying through Amazon DSP direct access to high-quality, curated supply, with better viewability, lower CPMs and higher ROAS. Our invite-only service provides transparency and efficiency for publishers and buyers—including Amazon DSP.

How do SSPs fit into the programmatic advertising ecosystem?

An SSP is an integral part of the programmatic advertising ecosystem, and is an important tool to help facilitate the buying and selling of digital ads. Here is how an SSP fits into this process.

Real-time bidding transactions

Real-Time Bidding (RTB) is a way to buy ads programmatically. With RTB, advertisers can participate in an auction when an impression becomes available. If their bid wins the auction, their ad is displayed on the publisher’s site. RTB is not only efficient, but it helps advertisers focus on the most relevant inventory. Through RTBs, publishers and advertisers are able to sell and buy ads facilitated by an SSP.

Supply path optimization

SSPs help publishers find the right demand sources to work with, based on factors like latency, unique demand, bid rates, and ad space availability.

Frequency capping

Frequency capping allows advertisers to limit the number of times an ad is shown to customers in a set period of time.

What are the main components of an SSP?

An SSP provides a number of important functions in the buying and selling of programmatic advertising. Here are some of the key features of the supply side platform.

Ad Exchange

An ad exchange allows SSPs and DSPs to communicate and facilitate the buying and selling of ads through real-time bidding transactions.

Analytics reports

SSPs provide detailed reports about the performance of the ad inventory, giving publishers the opportunity to optimize their campaigns.

Ad inventory management

An SSP gives publishers control over their inventory to manage the types of ads being sold.


SSPs can integrate with other Ad Tech so publishers can add even more nuanced insights to reach relevant audiences.

Header bidding

Header bidding is a technology that allows publishers to simultaneously request bids from multiple demand sources and increase yield. APS, for example, exclusively supports header bidding integrations so advertisers can maximize reach on publishers’ inventory, allowing APS to manage ad fills to control for competitive separation and frequency capping. Through our server-to-server integration, you will be able to request multiple bids at once, and have our bids provide additional demand managed in your ad serving system.

1 Statista, Global Programmatic Advertising Spending, 2021
2 eMarketer, Programmatic Digital Display Ad Spending Forecast, June 2021