The Sell Side Platform (SSP) is an AdTech platform used by the publishers to sell, manage and optimize the ad inventory in real time on their websites in an automated and effective way.
The SSPs are key players of RTB process and can be used to manage ad inventory, set price rules (like floor price, which is the minimum bid required to take the inventory slot) and sell the ad inventory to maximize revenues.
The SSP is used mainly by the supply-side, where the goal is to sell audience to advertisers whom – generally – are willing to pay the highest price to win the auction.
SSP is always an ad exchange, because it is connected to the demand source tech.
But not all ad exchanges are SSPs though. Some ad exchanges do not own the source code of the SSP, simply because they didn’t develop the tech themselves, but they use it on license or white label.
Why is this happening? Because building and maintaining an SSP and the consequent integrations to all demand sources requires time and lots of money! That is why some SSPs sell their core tech as a white label solution and allow players to customize the platform.
Of course, added intermediaries increase costs, which may put you at a disadvantage against publishers on other SSPs that have lower costs.