Free tool · Runs in your browser
Is your redaction real?
Drop a redacted PDF and find out in seconds whether the text under the black boxes is still in the file. The check runs entirely on your device. Your PDF is never uploaded.
Your file stays on your device. Nothing is uploaded.
PDF files up to 50 MB · the first 300 pages are checked
What the checker looks for
A redaction can look perfect on screen and still leak. These are the failures we see most often, and the checker tests each page for all of them.
Text under black boxes
A rectangle or a thick highlight drawn over the words hides them on screen, but the text stays in the file. Anyone can select it, copy it or search for it.
Redaction marks never applied
Many PDF editors mark areas first and remove the text only when you apply the redactions. If the file was saved before that step, everything under the marks is still there.
Boxes on top of a page picture
Some tools turn each page into a picture and lay black shapes on top. Delete a shape in a PDF editor and the original picture underneath shows everything.
Scans with a hidden text layer
A scan blacked out on the picture can still carry an invisible text layer with every word, added when the scan was made searchable.
Flattened pages
A page that is only a picture, with no text layer, has no hidden text to recover. The checker tells you which pages look flattened.
File properties
Title, author and the app that made the file travel with it. They often carry a client's or an employee's name, so the checker shows them as a note.
How to read the result
No text was found under boxes, annotations or unapplied redaction marks, and no boxes sit on top of a picture that still shows content. The check covers hidden text only: it does not judge whether what you left visible is sensitive.
Something you meant to hide can be copied, searched or recovered from the file. Do not send it. Redact the original again with a tool that removes the text, then check the new copy here.
Part of the file could not be checked, or it contains text that is invisible for another reason, for example printed in white. Look at the pages listed in the notes by hand.
Your file never leaves your device
When you drop a PDF, your browser reads it from your disk and a PDF engine that is part of this page (Mozilla's open-source pdf.js, served from blurdata.app) opens it in memory. No part of the file, and nothing found inside it, is sent to us or to anyone else. We only count that a check ran and which verdict it gave, so we know the tool is being used.
Want to see for yourself? Load this page, turn off Wi-Fi, then drop your file. The check still works, because there is nothing to upload.
What the checker can't see
It catches the failures behind most real-world leaks, but it is not a guarantee. Keep these limits in mind:
- Visible text. The checker does not decide what is sensitive. If a name was never covered, it will not tell you.
- Locked files. A PDF that needs a password to open cannot be checked. Save an unlocked copy first.
- Attachments, form fields and comments. Files attached inside the PDF, form field values and the text of comments are not checked.
- Pictures under pictures. A black box that is itself an image, placed over another image, is not analyzed.
- Very large files. Only the first 300 pages of files up to 50 MB are checked.
Before you send a sensitive document, also run the manual 60-second redaction check: search for a removed name with Cmd+F (Ctrl+F on Windows), copy across a black bar and paste it into a text editor, and look at the file properties.
Failed the check? How to fix it
Don't try to fix the redacted copy. Go back to the original and redact it again with a tool that removes the content from the file instead of covering it, then check the new export here.
That is what BlurData does on Mac. It finds names, account numbers, addresses and other personal data on every page, scans included, and exports a new PDF where the hidden text is gone from the file, not hidden under a box. It runs offline on your Mac, and your documents are never uploaded. If the file is going to ChatGPT or Claude, it can replace names with consistent labels instead of black boxes.
Frequently asked questions
Is my PDF uploaded when I use the redaction checker?
No. The file is opened by your browser and checked by a PDF engine that is part of this page. No part of the file is sent anywhere. You can load the page, turn off your internet connection and run the check: it still works.
How can a redacted PDF still contain the text?
A black rectangle or highlight drawn with markup or drawing tools sits on top of the text, which stays in the file. Anyone can select it, copy it or search for it. A real redaction removes the text from the file before the box is drawn.
What does Looks safe mean?
It means the checker found no text hidden under boxes, annotations or unapplied redaction marks, and no boxes sitting on top of a page picture that still shows content. It does not judge whether the text you left visible is sensitive.
Can it check scanned PDFs?
Yes. A scanned page with no text layer is reported as flattened. If the scan has an invisible text layer, the checker looks for words in that layer that sit under blacked-out areas, which is a common leak.
Is this checker a guarantee?
No. It catches the most common redaction failures, but it cannot see everything, for example content in file attachments or very unusual files. Use it together with a manual check before you send a sensitive document.