Buying and selling of ad impressions on an online auction marketplace (or ad exchange) in real time. Online publishers auction off their ad inventory at an individual impression level in real time via an ad exchange supply side platform or SSP. Advertisers use the ad exchange Demand Side Platform or DSP in order to bid in real time per impression. Advertisers or media buyers can target based on content that the user is looking at or behaviors that they have exhibited online. Real Time Bidding allows them to decide in real time the value of an ad impression and decide whether or not to bid for that impression. Real Time Bidding lets advertisers target audiences by individual impressions, and publishers receive higher yields for impressions.