A Sell-Side Platform (SSP) is a platform used by publishers to automate and optimize the sale of their advertising space. It allows them to efficiently market their inventory, including unsold space, by distributing it to various buyers such as ad networks and Demand-Side Platforms (DSPs). Often operating in real time, the SSP selects the best offer based on the visitor profile and ad placement to maximize publisher revenue. Its primary goal is to reduce unsold inventory and increase the cost per mille (CPM) of ad space.