Anonymisation vs Pseudonymisation
These two techniques both reduce risk, but they are not the same and the law treats them very differently. Confusing them is a common and costly mistake.
This is general guidance to help you use the right term — and the right technique — in your own systems.
The Key Difference
Anonymised data can never be linked back to a person, so it is no longer personal data and falls outside the UK GDPR. Pseudonymised data can still be re-identified with additional information, so it remains personal data and stays in scope.
When to Use Each
- Anonymise data you want to share or publish freely.
- Pseudonymise working data to limit who can identify people.
- Use anonymisation for long-term analytics where identity is irrelevant.
A Word of Caution
True anonymisation is harder than it sounds. Combining supposedly anonymous datasets can re-identify individuals, so test your approach before relying on it.
Frequently Asked Questions
If I replace names with ID numbers, is that anonymous?
No — that is pseudonymisation. If you hold the key linking IDs to names, the data is still personal data.
If you need a hand with any of this, your Progressive Robot delivery team is ready to help. Raise a ticket from the Support area of your client portal or speak to your account manager and we will guide you through the next steps.