Although Safari was designed to block such cookies, Google found a workaround for that blocking so it could continue to fully monetise those users.
Sir Geoffrey Vos, a senior judge, described the case as seeking "to call Google to account for its allegedly wholesale and deliberate misuse of personal data without consent, undertaken with a view to commercial profit" in a judgment from last year allowing the case to go ahead.
"Google takes the data regardless of whether the user actually clicks on a Google-supported advertisement – or even knows of its existence," states the legal claim.
The complaint, filed in Northern California yesterday [PDF], claims that through a combination of means ranging from "Google Analytics, Google Ad Manager, and various other application and website plug-ins", the adtech company has identified individuals' IP addresses, "what the user is viewing, what the user last viewed, and details about the user's hardware" while they were in incognito mode.
Google has been sued for billions of dollars in a proposed class action alleging the adtech company identified and tracked users who adopted its browser's incognito mode to avoid such tracking.