Pseudo-anonymisation vs Anonymisation: What’s the Difference?

Pseudo-anonymisation vs Anonymisation: What’s the Difference? is a question we were asked this week.

When handling personal data, there are two main methods for de-identifying individuals – pseudo-anonymisation and anonymisation. But what exactly do these terms mean and how do they differ?

Pseudo-anonymisation refers to replacing direct identifiers (like names) with indirect ones (like numbers). So in a pseudo-anonymised list, each individual is still assigned a unique code but this can be mapped back to their real identity. This allows the data to be analysed on an individual level while protecting direct identifiers but you could verify the data with the original information if you wanted to.

For example, let’s say we have a list of 100 email subscribers. If we replace the names and email addresses (the personally identifiable information) with numbers (Subscriber 1, Subscriber 2, etc), the list is now pseudo-anonymised. We can still analyse data per subscriber, but without exposing their identities.

In contrast, anonymisation removes all identifiable information and it cannot be mapped back to the original record. The data is aggregated and individual-level analysis is no longer possible.

Going back to our subscriber list example, anonymisation would mean reporting statistics for the whole group (“50 subscribers opened the last email”) rather than per subscriber. There is no way to connect any information back to a specific individual.

So in short:

Pseudo-anonymisation = individuals still have a unique code, allows for individual-level analysis but this can be mapped back to the individuals information.
Anonymisation = all identifiable info removed, only high-level analysis possible and cannot be mapped back to a specific individual.

The appropriate method you would use will depend on the purpose you are trying to achieve. It is possible to use both techniques carefully and this allows for useful data analysis while respecting privacy.

If you have questions about data privacy strategies, please contact us here and if you want to find out more about Your GDPR Advisor, you can find it here.