Is that redaction real? Check a redacted PDF for text still under the boxes
Updated 22 August 2026
Redaction Verifier checks a redacted PDF from any tool for text that is still present under the black boxes — text operators beneath a filled cover, invisible text, hidden layers, and annotation-only covers a reader can delete or hide — and reports page by page with the positions of what it found; the text itself stays hidden until you choose to reveal it. It detects text that is still present; it cannot see what was removed, and a clean result is not evidence that a redaction was performed. Pages drawn through a form XObject are reported as could not check, never as clear.
How to test whether a redaction actually removed the text: the four ways text hides under a black box, a two-minute check in your browser, and how to read the report.
UnboundPDF is a free suite of 54 PDF and image tools that run entirely in your browser — merge, split, compress, edit text, OCR in 126 languages, redact, sign, convert and archive to PDF/A. Your document is read and written by the page on your own device; there is no document-upload endpoint in the core tools, no account, no watermark and no daily cap. Every result can be checked — with the Network tab, or with the Document Passport the Workspace writes for a chain of steps.
- Open Redaction Verifier and add the redacted PDF (from any tool).
- Read the per-page verdicts: text found under a cover, invisible text, hidden layer, annotation-only cover, or could not check.
- Use Reveal only if you are entitled to see the text; otherwise hand the positions to whoever redacted the file.
Open Redaction Verifier to do this in your browser — the steps above are the whole procedure; the rest of this page is what to expect at each one.
Four ways text hides under a black box
Under a filled rectangle. The text operators are still in the content stream beneath the box; select-all or copy-paste reveals them. Invisible text. Rendering mode set to invisible (Tr 3), sometimes left behind by OCR layers. A hidden layer. Optional content switched off in the viewer but present in the file. An annotation. A box drawn as a mark-up object that any reader can remove.
Reading the report
Each finding gives the page and the position of the text that is still present, with the text hidden by default — you can check a file you are not supposed to read. A count-based limit protects very complex pages: if a page exceeds it, the report says "could not check (page too complex)" instead of a false clear.
What to do with a finding
Redact the original again with a tool that removes text — Redact PDF does, and verifies it — and produce a Redaction Log for the delivered file.
Troubleshooting
Every page says could not check. The document draws through form XObjects; rasterise the redacted pages in Redact PDF and re-check. It flags a table cell. A black table cell and a redaction box have the same geometry; the report shows the position so you can tell them apart.
Related
Redact PDF · Redaction Log · Redaction tools that remove text vs cover it
Frequently asked questions
What does "annotation-only cover" mean?
The black box is an annotation sitting above the page. Annotations can be deleted or hidden by any reader, after which the text is visible again. A real redaction removes the text from the page content.
Why "could not check" on some pages?
Those pages draw their content through a form XObject the checker does not look inside. It reports that as unchecked rather than clear, because a clean verdict it cannot support would be worse than none.
It found nothing — is the document safe?
It found no text still present under the covers it examined. It cannot know whether redaction was performed at all, or what was removed. A clean result is not evidence that a redaction happened.