There are several protocols for targeting specific interest audiences. Firstly; most Data Management Platforms (or: DMP) provide interest preferences of smartphone users. These are collected via cookie protocols (mobile web) or Device-ID protocols (in-app). The collection (or: crawling) of user preferences roughly comes down to publishers that are visited, specific content that is clicked on - and/or products that are bought. These preferences are stored and can be targeted upon using a good Demand Side Platform which is integrated with a Data Management Platform.
-Please note that we don’t offer third party data targeting - using a DMP - in Europe (do to the GDPR).