Cross-contexts inference is central to the profiling and targeting capacities of advertisers. They draw on information gleaned about individuals from the different social contexts of the web, in ways that violate users' privacy according to the theory of contextual-integrity. To measure this violation, we offer a context-sensitive empirical study of the usage of persistent-identifiers by third-party trackers. We applied an instrumented FireFox browser and launched six browsing experiments across three social contexts: news, health, education. We ask how social contexts of websites explain persistent identification? And should we expect trackers from certain contexts to become more likely to link user identities across contexts? Our findings show that social contexts matter. Third of the observed third-parties had persistently identified users among social contexts. This is happening in all three contexts, between every pair of websites. Trackers from the healthcare context are the most..