DSP vs SSP. two parties are involved in the process of purchasing advertising in programmatic. They are the sell-side and buy-side.
On the seller’s side, there are SSP (Supply / Sell Side platform, a platform for selling advertising space on publisher sites), Ad Exchanges and Ad Networks.
In its turn, DSP (Demand Side Platform) is working in the interests of the buyer.
Supply Side Platform (SSP) is a platform that sells advertising equipment or advertising positions of websites. SSP aggregates site offers, “collects” residual traffic and also sets the minimum cost at which the site is ready to implement the impression. SSP holds an auction bargaining with DSP, selling the inventory of the publisher as profitably as possible.
Demand Side Platform (DSP) is a platform for the automatic purchase of online advertising. It directly interacts with the SSP, Ad Networks, Ad Exchanges and publishers.
The main DSP goal is to buy advertising at the best price and to show ads to users who exactly matches the needs of advertisers.
So the main difference is that SSP is used by online publishers to automate the sale of advertising space or site. In other words, this is an analogue of DSP only for the supply side, not for the demand side.
If DSP users want to buy the most relevant advertising space at the lowest rate, then SSP aims to maximize the price in the interests of publishers. Both platforms are based on the same engines.