How does Quantcast Advertise work?

We start with a set of customer archetypes that best represent an audience segment. These archetypes can come from an advertiser’s first-party data, or online/offline transaction data from trusted providers. The customer archetypes act as ‘reference points’ for our targeting technology to find more consumers who look just like the archetypes.
Factoring in billions of observations, we identify the distinctive characteristics of the customer archetypes to build a unique audience model. The model is then compared to the entire online population, finding users who match those characteristics– this creates a unique audience segment that can be targeted across your inventory.

As a result, advertisers reach only the best customer prospects, even as online audiences change.