Pseudonymization

Pseudonymization means replacing a person's direct identifiers with an artificial one, so the data is no longer directly tied to the person but, with a separate key, can still be re-linked.

Pseudonymization should not be conflated with full anonymization, and the difference is vital: in true anonymization the link to the person is destroyed forever and no return is possible; in pseudonymization the link is only hidden and can return with a separate key. The important legal consequence is that pseudonymized data still counts as personal data, because a path to re-identification still exists; so pseudonymization is a risk-reduction measure, not an exemption from privacy rules. Its value is that if the data leaks, it is meaningless without the key, and a team's day-to-day access does not need the user's real identity. The common trap is selling pseudonymization as “anonymous”; if a raw IP or email is still kept somewhere, the anonymity claim is false.