How the check works
- Open the PDF above. A sample with a failed redaction is under Try a sample.
- The tool reads every character the PDF exposes to copy and paste, renders each page, and looks at the pixels under every character.
- Where a character can be copied but its area is solid black, it is reported as text still under a black box and marked for real redaction.
- It also lists hidden data that came with the file: document info, comments, form fields, attachments, scripts and bookmarks.
Common ways redaction fails
- Black rectangles or highlights drawn over text in a PDF editor or in Word before exporting.
- Redaction marks never applied. Some editors mark areas first and remove them only when you apply; a file saved in between has the marks but not the removal. The checker reports these as “marked for redaction but never applied”.
- Black-filled comment boxes or form fields placed on top of the page.
- The name in the metadata. The page is clean but the document title or author still says who it is about.
- The same thing elsewhere. A name boxed on one page but printed in full in a footer or on another page.
The tool’s own exports are checked for all of these before you download them. Read more about blacking out text properly.
Questions people ask
How can I tell if a PDF was redacted properly?
Open it above. The tool renders every page and checks every piece of selectable text: if text can be copied but sits under something solid black, the redaction failed, and it tells you how many places and on which pages. You can also check by hand: select across a black bar, copy, and paste into a text editor.
What does it mean if it finds hidden text?
The black boxes in that file are only shapes drawn over the text. Anyone who receives the file can copy the text out or find it with search. The places it found are marked as redactions, so you can tap Redact and check to make a version where that text is really removed.
Does a clean result mean the PDF is safe to share?
It means no text was found under dark boxes. Also check the “Hidden data removed on open” list: names often survive in the document title, author, comments, bookmarks or attachments. Exporting with this tool removes those too, and the final check covers them.
Can it see redactions that use white boxes?
Not as hidden text. White-on-white or text covered by a white shape looks like an empty page, and the checker only looks for text under dark areas. If a document looks like it has gaps, search it for words you expect to be gone.
Is the PDF I check uploaded?
No. The check runs in your browser. Nothing about the file is sent anywhere.