“Perhaps more concerning, the researchers found that even users who explicitly opt out of tracking under privacy laws like Europe’s General Data Protection Regulation (GDPR) and California’s California Consumer Privacy Act (CCPA) may still be silently tracked across the web through browser fingerprinting.”
Researchers changed browser fingerprints and watched ad bids move. That is the first hard proof fingerprinting feeds ad targeting. Clearing cookies did nothing. Opting out under GDPR and CCPA did nothing either.