---
title: "What is pseudonymization?"
description: "Pseudonymization swaps names for codes but keeps a key. Why the GDPR still treats it as personal data, and what that means for licensed documents and code."
canonical_url: https://www.fearofgod.ai/glossary/pseudonymization
last_updated: 2026-10-26
site: "fearofgod.ai"
lang: en
---

# What is pseudonymization?

Pseudonymization is the replacement of names and other direct identifiers in a dataset with codes or aliases, while the key that links them back to real people is kept separately.

## How is pseudonymization different from anonymization?

Pseudonymised data can still be linked back to a person by whoever holds the key; anonymous data cannot. The GDPR defines pseudonymisation as processing personal data so that it "can no longer be attributed to a specific data subject without the use of additional information", which must be kept separately and protected ([GDPR Article 4(5)](https://www.legislation.gov.uk/eur/2016/679/article/4/adopted)). Recital 26 adds that pseudonymised data which could be attributed to a person with that extra information "should be considered to be information on an identifiable natural person", so the regulation still applies to whoever can make that link ([GDPR Recital 26](https://www.legislation.gov.uk/eur/2016/679/introduction/adopted)). Citing the EU Court of Justice in EDPS v SRB (C-413/23 P), the European Data Protection Board's draft anonymisation guidelines say anonymity "should be assessed from each relevant entity’s perspective" ([EDPB Guidelines 02/2026](https://www.edpb.europa.eu/system/files/2026-09/edpb_guidelines_202602_anonymisation_v1_en_0.pdf)). The European Data Protection Board consulted on draft guidelines on pseudonymisation from January to March 2025 ([EDPB Guidelines 01/2025](https://www.edpb.europa.eu/public-consultations/guidelines-012025-on-pseudonymisation_en)).

## Where does pseudonymization show up in SOPs, documents and code?

Mostly in records written by and about people. A ticket export can turn every customer into a stable code, chat archives can replace staff names with their roles, and commit history can swap author names and emails for hashed IDs. Stable pseudonyms keep the record readable: a model can still see that the same customer wrote back three times, or that one reviewer approved a whole module. That same consistency is why it is not anonymity, since the key, or enough surrounding detail, can lead back to the person.

## What does pseudonymization mean for what you license and control?

Whoever holds the key controls re-identification, so who keeps it is worth settling before any records are shared. Because pseudonymised records may still be personal data under the GDPR, the lawful basis for sharing them and the licence terms still matter; ask counsel about your own records. fearofgod.ai de-identifies the data before it goes to buyers. Raw data is deleted according to a schedule agreed with the partner.


## Related

- [Anonymization](https://www.fearofgod.ai/glossary/anonymization)
- [De-identification](https://www.fearofgod.ai/glossary/de-identification)
- [PII redaction](https://www.fearofgod.ai/glossary/pii-redaction)
- [Your chat and email archives are worth licensing](https://www.fearofgod.ai/sell/chat-and-email-archives)
- [Is it legal to sell company data to AI?](https://www.fearofgod.ai/guides/is-it-legal-to-sell-company-data-to-ai)

---

Source: https://www.fearofgod.ai/glossary/pseudonymization · Index for AI systems: https://www.fearofgod.ai/llms.txt · Contact: sean@fearofgod.ai