Is your PDF really redacted?
Drop a redacted PDF to see whether text is still hiding under the black boxes. The check runs in this tab and the file is never uploaded. Turn Wi-Fi off and try it.
- Never uploaded
- Works with Wi-Fi off
- Free, no account
What the checker looks for
- Text under a black box. A rectangle drawn on top hides the words on screen, but they stay in the file.
- Covered or invisible text. Text under a white box, or typed in white on a white page.
- Redactions never applied. Areas marked for redaction in an editor, where the final "apply" step was skipped.
- Metadata. The author, title, software and other details saved inside the file.
Why black boxes fail
A PDF stores text and drawings separately. When you draw a black rectangle in a PDF editor, or highlight text in black in a word processor and export it, the shape is painted over the letters. The letters themselves are still there. Anyone who receives the file can select the area, copy it and paste it somewhere else, or search for a word and land right under the box.
This is how lawyers, governments and companies have leaked names and numbers in documents they believed were redacted. It is also the most common mistake with payslips, bank statements and ID copies sent to landlords or employers.
The copy-paste test, by hand
- Open the redacted PDF in any viewer.
- Select all the text with Ctrl+A (Cmd+A on a Mac) and copy it.
- Paste into a plain text editor. If the redacted words appear, the redaction did not work.
- Then open the document properties (Ctrl+D in most viewers) and read the author and title.
The checker above does the same thing for every word on every page, and tells you where the problems are.
How a real redaction works
A redaction is real when the information is gone from the file, not just covered. Good tools remove the text under each box, delete metadata and attachments, and often flatten each page into an image so nothing can be selected. Sumi does it this way: you review what it found, then each page is redrawn as an image with the ink painted into the pixels, and a new PDF is written with no text layer and no metadata. Like this checker, it runs entirely in your browser.
Questions
Is my PDF uploaded?
No. The file is read and checked by code running in this browser tab. You can turn Wi-Fi off after the page has loaded and the check still works.
Can the check miss something?
Yes. It looks for text that is in the file but not visible on the page. It does not see pictures under a black box (a scanned page covered with a shape can still contain the full image), text inside attachments, or earlier versions of an edited file. A clean result is a good sign, not a guarantee.
It found a leak. What do I do?
Don't send the file. Go back to the original, redact it with a tool that removes the text (not one that draws on top), then run the check again on the new file.
Does it work on scanned documents?
It checks the text layer. Scans that were run through text recognition have one, and it is checked like any other text. A scan with no text layer is only pictures, so there is no hidden text to find, but if a box was drawn over the picture, the full picture can still be underneath: see the previous answer.
Is it free?
Yes, with no account and no page limit. Redacting with Sumi is free for documents up to 10 pages.