Guides
Redaction advice is mostly repeated badly. These pages take one question each and answer it properly, including the cases where the usual advice fails.
Concepts and technique
- Redaction vs Blur: Which One Actually Removes the Information
The two terms are used interchangeably in most tool interfaces, which is exactly why redacted documents keep leaking. They are not the same operation and they do not produce the same file.
- Is Blurring Text in a Screenshot Actually Safe?
Short answer: for credentials and identifiers, no. For backgrounds and crowds, often yes. The difference is not the strength of the blur, it is what is underneath it.
- Remove EXIF and GPS Data by Re-Encoding the Image
You can hide a face in a photo and still publish the coordinates where it was taken. EXIF is the part of the file nobody looks at, and it is often the most specific information in it.
- What Does Redact Mean?
The word comes from editing, not from secrecy. To redact a document is to prepare it for release by removing the parts that should not be published — and the operative word is remove.
Two ideas that cover most of it
Almost every redaction failure comes from one of two mistakes, and neither of them is about how strong the filter was.
The first is choosing an operation that transforms instead of removes. A blur, a mosaic, and a lightly applied smear all leave a residual in the exported file. For a long paragraph that residual is harmless. For a six-digit code it is not, because the candidate space is small enough to enumerate and the field itself often carries a checksum to verify against.
The second is reviewing the wrong artifact. People check the editor, where a box composites over an image in memory, and ship the file, where the export path decides what actually gets written. Those two things can differ, and the file is the one a recipient receives.
Everything else — which fields to cover, what metadata survives, why a PDF behaves differently from a PNG — follows from those two points.
What to hide, by document type
About the tool behind this site
Everything described here is what the redaction tool on this site actually does, which is why the pages are specific about limits instead of claiming that redaction is solved.
- How auto-detect decides what to flag — the six pattern rules, the checksum, and the misses.
- Security audit — what the tool sends, and the one outbound request it makes.