Real-time bidding is an auction that completes in milliseconds when an ad impression becomes available: the SSP sends a bid request, DSPs evaluate the user and context, and the highest eligible bid wins. Most display and video open-exchange inventory is RTB-priced. CPM varies by audience quality, viewability, and competition.
Not all programmatic is RTB — guaranteed and fixed-price PMP deals skip the open auction.
Sources
Last verified Jun 5, 2026