What is redaction?
Redaction is the removal of sensitive details from a document, picture or recording before someone else sees it. The rest of the content stays readable, so the reader still gets what they need, minus the parts they have no right to.
The word comes from legal and government work, where court filings and released records have names, account numbers and other private details blacked out. Today it applies to any file: a screenshot sent to a support team, a spreadsheet handed to a contractor, a call recording used for training.
Redaction, deletion and anonymisation
- Deletion gets rid of a whole file or record.
- Redaction keeps the file and removes selected parts of it, usually leaving a visible mark (a black bar, a label such as [NAME], or a beep) so the reader knows something was taken out.
- Anonymisation goes further: a dataset is changed until nobody in it can be identified, even by combining fields. Redacting names alone often falls short of that.
Methods that leave the data behind
Most failed redactions look fine on screen. The sensitive text is still in the file, just out of sight:
- Black highlighter or a shape on top. The words underneath can be selected, copied or found with search. See why black boxes in PDFs fail.
- White or tiny text. Changing the colour or size hides nothing from a copy and paste.
- Blur and pixelation. Short strings such as numbers can sometimes be rebuilt by trying every candidate and comparing the blurred result.
- Cropping. Some apps keep the cropped area inside the file, so it can be restored.
- Forgetting the hidden parts. Comments, tracked changes, speaker notes, hidden sheets, document properties and photo location data travel with the file.
What a proper redaction does
- Replaces the sensitive characters, pixels or sound in the file itself, not in a layer above them.
- Covers every copy: headers, footers, alt text, chart labels, cached values and earlier versions.
- Strips metadata such as author names, GPS coordinates and editing history.
- Is checked afterwards, by searching the output for the removed terms.
When people redact
- Answering a data subject access request or a freedom of information request.
- Filing court documents or sharing evidence.
- Sending bank statements, payslips or ID to a landlord or lender, with the irrelevant parts removed.
- Posting screenshots, bug reports or logs in public places.
- Giving datasets or recordings to vendors, researchers or AI tools.
The personal information checklist lists what to look for in each case.