Find text still hiding under black boxes before you send a PDF, or after you receive one.
Use this tool free →Most failed redactions look perfect. Someone draws a black rectangle over a name or a number, the page looks blacked out, and the file is sent. But the rectangle is only drawn on top: the text underneath is still in the PDF, and anyone can select it, copy it, or search for it. NilPDF Check Redaction reads the document the way a script would and reports any text that is covered by a shape or image drawn over it, any redaction mark that was never applied, and any text kept in an earlier saved version of the file. It works on the redacted file alone, so you can check a document before you send it or one you have been sent. Everything runs in your browser, so the file you are checking is never uploaded.
Drawing a black box, whether with a shape tool, a highlighter set to black, or a comment, only adds a rectangle on top of the page. The text it covers is still stored in the file underneath, so it can be selected, copied or extracted even though you cannot see it. This is how redacted material has repeatedly leaked from court filings.
Your files never leave your device. All processing happens in your browser using WebAssembly (Pyodide). NilPDF has no server, there is nothing to upload to.
Yes. The check runs entirely in your browser. The PDF is never uploaded to any server, which matters here more than anywhere: the file may contain exactly the information you are trying to protect.
It means no text is hiding under boxes, in unapplied redactions, or in earlier saved versions. It cannot see inside images, so if a scanned page was blacked out in the scan itself, those pixels are simply gone or simply there. Also review the document properties it lists, which can reveal names or titles.
Redact it with a tool that removes the content rather than covering it. NilPDF Redact rebuilds each marked page so the covered text is no longer in the file, and you can run this check again afterwards to confirm.