Click to upload or drop a PDF here
One PDF — checked in your browser, never uploadedAbout Check PDF Redaction
A "redacted" PDF often has a black box drawn on top of the words. The words are still in the file. Anyone can select them, copy them, or pull them out with a text extractor.
This tool checks your file for that mistake. It reads every piece of text in the PDF and looks at the page to see if it can really be seen. If a word sits under a black box, the tool finds it and shows you the word. Your file stays on your device. Nothing is uploaded.
Features
- Finds text under black boxes — checks each letter, so a box that covers only part of a line is still found
- Finds invisible text — white text on a white page, and text covered by a plain box
- Finds text off the page — words placed outside the part you can see
- Page preview — red outlines show where the hidden text sits
- Other leaks — author, title, XMP data, comments, unapplied redaction marks, form values and attached files
- Copy and save the list — one click to copy the findings or save them as a text file
- Clear answer — a red, amber or green banner tells you if the file is safe
- Private — the check runs in your browser
How to use it
- Click Click to upload or drop your redacted PDF on the page
- Wait while each page is checked. A long file takes a little longer
- Read the banner at the top. Red means hidden text was found
- Look through the list. Each line shows the page and the hidden words
- Use the page preview to see the red outlines on the page
- Press Copy findings to keep the list, or download it as a text file
How a bad redaction happens
Most tools that "redact" only add a shape on top of the page. The page now looks right, but the text is still in the file. These are the usual ways it goes wrong.
| What was done | Is the text gone? |
|---|---|
| Black rectangle drawn over text | No. The text is still there |
| Text colour changed to white | No. The text is still there |
| Highlight set to black | No. The text is still there |
| Page printed to a new PDF | Yes, if it was printed as a picture |
| Page rendered to a picture | Yes. This is the safe way |
What else can give you away
The page is not the only place where private data hides. This tool also lists:
- Document info — the title, author, subject and the program that made the file
- XMP metadata — a second block of data that often repeats the author and title
- Comments and notes — sticky notes and text boxes that were added on top of the page
- Redaction marks — a "Redact" annotation that was added but never applied
- Form fields — text typed in a fillable form can stay in the file
- Attached files — a PDF can carry other files inside it
How to redact a PDF properly
The safe way is to turn each page into a picture, with the black boxes painted into the picture. Then there is no text left to copy. Use Redact PDF for this. After that, run this check again on the new file. It should show no text at all, or no hidden text.
Frequently asked questions
How does the tool find hidden text?
It asks the PDF for every piece of text and its position. Then it draws the page and looks at the spot where each letter should be. If the spot is solid black, or has no contrast at all, the letter cannot be read by a person, but it is still in the file. That is hidden text.
Why does it say there is no text at all?
Then every page is a picture. That is what a properly redacted file looks like. It is also what a scan looks like. A picture has no text layer, so there is nothing to find.
Can it see text inside a scanned page?
No. Words inside a picture are only pixels, not text. This tool reads the text layer. If you need to know what a scan says, use an OCR tool. If a person can read the text on the page, a person could read it before too.
Does the green banner mean the file is 100 percent safe?
It means no hidden text was found. The words around a black box can still give hints, and the check cannot see inside pictures. Also read the list of other leaks, such as the author name.
Is my PDF uploaded?
No. The file is opened and checked in your browser. Nothing is sent to a server.
Why was a normal word flagged?
A very dark photo or a black bar can look like a box. If the text on it is meant to be there, you can ignore it. Check the preview to see.
Good to know
- The check works best on PDFs made from documents. It cannot read text in pictures
- A password-protected PDF has to be unlocked first with Unlock PDF
- Text is judged letter by letter, so very wide or unusual fonts may be a little off at the edges
- Only the first 300 pages are checked
- Always keep your original file. Redact a copy
- You can try it on a file you trust first, to see how a failed redaction looks
Related tools
- Redact PDF — burn the pages into pictures so the text is really gone
- PDF to Text — see all the text a PDF holds, the way a copy and paste would
- PDF Metadata Editor — view and change the author, title and other fields
- Flatten PDF — turn comments and form fields into fixed page content
- Compare Two PDFs — see what changed between the original and the redacted copy
- Protect PDF (Add Password) — put a password on the file you send
