ISC Privacy · Updated November 2026
Anonymous or Pseudonymous: Can the Person Still Be Reidentified?
The key question is whether the data can still be linked back to a person using additional information.
Pseudonymization
Identifying information is replaced or transformed so attribution requires additional information, but reidentification remains possible.
Anonymization
The goal is to transform information so individuals cannot reasonably be identified under the applicable standard.
Why names are not enough
ZIP code, birth date, location, occupation, and other attributes can sometimes reidentify someone even after names are removed.
Privacy value
Both techniques can reduce risk, but they do not create identical privacy or legal consequences.
The takeaway
Pseudonymized data can often be reidentified with additional information. Proper anonymization aims to prevent reasonable reidentification.
Related Summit guides
FAQ
Is replacing a name with an ID always anonymization?
No.
Can pseudonymized data remain personal data?
Yes in many frameworks.
Does anonymization require reidentification analysis?
Yes.