What is a DSP vs SSP?
A DSP (demand-side platform) is software advertisers and agencies use to buy ads automatically across many publishers, deciding which impressions to bid on and how much. An SSP (supply-side platform) is software publishers use to sell their ad space, running auctions and connecting to many buyers. The DSP represents the buyer; the SSP represents the seller.
A DSP such as The Trade Desk, Google's Display & Video 360 or Amazon DSP holds the advertiser's budget, targeting, frequency capping and bidding algorithms. An SSP such as Magnite, PubMatic, Index Exchange or Google Ad Manager's exchange tries to get the publisher the highest price for each impression, applying floor prices and brand rules.
They meet in the auction: the SSP sends a bid request, DSPs return bid responses, and the SSP picks a winner. Each takes a fee, which adds to the ad tech tax. The lines are blurring: some companies own both sides, and buyers increasingly connect directly to publishers through supply path optimization and curation.