What is redaction? A practical explanation
Redaction means permanently removing information from a document before sharing it. How it differs from blurring, where it goes wrong, and how to check it.
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Open Redact PDFRedaction in one sentence
Redaction is permanently removing information from a document so the version you share no longer contains it, while the rest of the document stays readable.
The black bars you see on released documents are the visible part. The important part is invisible: the words under the bars must actually be gone from the file, not just hidden from view.
Redaction, masking, blurring and deleting
| Term | What it means | Example |
|---|---|---|
| Redaction | Remove information permanently, usually leaving a box where it was | Blacking out an account number on a statement |
| Masking | Hide part of a value and keep the rest | Showing only the last 4 digits of Aadhaar or a card |
| Blurring or pixelating | Make an area unreadable by smearing pixels | Blurring faces in a photo |
| Deleting | Remove content and close the gap | Cutting a paragraph from a draft |
Masking and blurring are both forms of redaction when they're done in a way that can't be reversed. Blur is fine for faces but risky for short numbers; see Can blurred text be unblurred?.
Where redaction goes wrong
- Boxes drawn on top. A shape added in a PDF viewer or word processor covers the text visually, but the text is still in the file and can be copied out.
- Hidden data left behind. Metadata, comments, form fields and attachments can hold the same information.
- Missed repeats. A name hidden on page 1 but left in the footer of page 7.
- Light blur on numbers. Digits in a known font can sometimes be guessed back.
How to redact a document properly
- Open the file in Redact PDF. Images and screenshots work too.
- Review the personal details found automatically, and use find and redact to cover every occurrence of a word or phrase.
- Draw boxes over anything else, such as signatures or photos. Use Solid for text.
- Export. Each page is rebuilt from pixels, so the text under the boxes no longer exists, and metadata is removed.
- Check the result: try to copy the hidden text, or use the PDF Redaction Checker.
For more on checking, see how to check if a PDF is redacted.
Questions
Is redaction the same as censorship?
The technique is the same, but redaction usually means removing specific sensitive details, like personal data, so the rest of a document can be shared.
Can redaction be undone?
Proper redaction can't, because the information is no longer in the file. Boxes drawn on top can be removed, which is why checking matters.