Free tool
Is there still text under your black boxes?
A black box drawn over text hides it on screen, but the words can often still be selected and copied. Check a redacted PDF before it goes out. Your file never leaves your browser.
Runs in your browser — nothing is uploaded
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How the check works
Every page is drawn exactly as a PDF viewer would draw it, comments and annotations included. Then each piece of selectable text is compared with what's visible at that spot. Text that can be selected but sits under a solid dark area is a failed redaction. Text printed on top of a dark background, like a white table header, doesn't count, because you can see it.
The idea comes from Free Law Project's x-ray, built to find bad redactions in court filings. This version runs in the browser, so a privileged document never goes to anyone's server to be checked.
How to redact a PDF properly
- Use a redaction tool, not a drawing tool. In Adobe Acrobat Pro: Tools → Redact, mark the text, then Apply. Acrobat removes the text underneath. A black rectangle, black highlight or black text box removes nothing.
- Sanitize the file. Acrobat's “Remove hidden information” strips metadata, comments and earlier versions that redaction alone leaves behind.
- Or print to image. Flattening every page to an image leaves no text layer to leak, though the result is no longer searchable.
- Check the copy you send. Run it through this checker, then try to select and copy the redacted lines yourself.
Questions
Redaction, answered
Drawing a black rectangle over text, or highlighting it in black, only covers the words on screen. The text is still in the file underneath. Anyone can select it, copy it into another document and read it. A real redaction removes the text from the file itself.
No. The PDF is opened and drawn by pdf.js inside your browser tab. There is no upload and no network request carrying the file. To confirm it, open your browser’s developer tools, switch to the Network tab and run a check.
It finds text under dark boxes, including boxes added as comments or annotations. It does not inspect document metadata, earlier saved versions (incremental saves), comments, bookmarks or file attachments, and it can’t read text inside images. Use your PDF editor’s sanitize step for those.
Free Law Project’s x-ray tool, which they built to find bad redactions in court filings. This page does the same kind of check in your browser, with no Python and no upload. Credit for the idea is theirs.
Don’t send that file. Redact again with a real redaction tool (in Acrobat: Redact, mark the text, then Apply), save to a new file, and run this check on the new copy. If a bad copy has already gone out, tell whoever is responsible for the matter.