Why a black rectangle is not enough
In a PDF, a black rectangle is simply another drawing instruction. The text sits underneath it, unchanged — still selectable, still copyable, still searchable. Drag across the bar, paste it somewhere, and you have the words back.
This is not a hypothetical. Court filings, government reports and signed contracts have all been published with “redacted” passages that anyone could read by selecting the text.
What this does instead
- Renders the page you marked as an image, with the black bars painted into the pixels
- Rebuilds the PDF with that image in place of the original page
- Reads the text back out of the finished file and confirms the marked words are no longer in it
Step three is the one that matters. Any tool can claim it worked; this one checks and shows you the result.
The trade-off, stated plainly
A flattened page is an image, so its text is no longer selectable or searchable and the file is larger. That is the cost of the text genuinely being gone. Pages you did not mark are left exactly as they were, so a one-line redaction in a long report only affects the page it is on.
Does it work offline?
Yes. The PDF engine is served from this site rather than a CDN, so once the page has loaded there is no network involved at all.