Redaction, pseudonymization, anonymization: what's the difference?

People say "anonymize this file" when they usually mean "take the names out". The difference matters, because a document can have every name removed and still point to one person.

Redaction: removing specific details

Redaction means removing selected information from a document before it is shared: a name, an address, an account number, a paragraph. The rest stays readable. It is the most common need in practice: sending a file to a colleague, a supplier, an insurer, a lawyer or an AI tool, without the details they do not need.

Good redaction removes the information from the file, not just from view. See how to redact a PDF so the text can't be recovered.

Pseudonymization: replacing identifiers with labels

Pseudonymization replaces each identifier with a code or a label, such as "Client A", "Person 1" or "Account 3". The document stays easy to follow, because the same person keeps the same label throughout. But somewhere a key links the labels back to the real people, or the labels can be matched with other information. Whoever has that key, or enough context, can put the names back.

For that reason, privacy laws generally still treat pseudonymized information as personal information. In Québec, the law speaks of "de-identified" information: it no longer identifies a person directly, but it is still personal information. In Europe, the GDPR draws a similar line.

Anonymization: no way back

Anonymization is a much higher bar. Information is anonymous when it can no longer identify a person, directly or indirectly, and the process cannot reasonably be reversed. Québec's private-sector privacy law uses this kind of definition and sets strict conditions around it; it is not a label to apply lightly.

For a single document, reaching that bar is hard. Removing names and numbers is necessary, but the context can still point to someone: a rare job title, a small town, a date, an unusual event, or simply the fact that the reader already knows who was involved.

Which one do you need?

• To share a document without certain details: redaction, followed by a careful review.
• To keep a document readable while hiding who is who, for example for analysis: pseudonymization, with the key kept protected and separate.
• To treat information as no longer personal: anonymization in the legal sense, which usually calls for an assessment that goes beyond a single tool. Ask your privacy officer or legal adviser.

This article is general information, not legal advice.

Where Anonyma fits

Anonyma is a redaction tool. It finds personal information in your documents and removes it on your computer, then writes a new, cleaned copy; nothing is uploaded. It does not promise to make a document anonymous: the size of a box can hint at the length of the hidden word, and the context can still point to a person. You review every page and decide what is enough for the person who will receive the file.