Documentation on Prebid, incl. personal identifiers and ID databases companies use to track+follow people on the web and beyond, in part without relying on third-party cookies, incl Criteo, DigiTrust/IAB, ID5, LiveRamp, LiveIntent, Parrable, TheTradeDesk
http://prebid.org/dev-docs/modules/userId.html
[protecting people by good design, solid security, efficient processes and trusted services]