Why does copying text from under a black box work?

Many PDF editors add a black rectangle as an annotation or shape on top of the page. The text underneath stays in the page content, so search and copy still find it.

My redacted PDF has no searchable text at all. Is that normal?

Yes, if the pages were flattened to images. It is the safest kind of redaction. If the recipient needs searchable text, use a tool that removes only the redacted text, such as Acrobat's Redact tool, and run the tests again.

Do I need to check scanned PDFs?

Yes. Some scanners and PDF apps add an invisible OCR text layer to scans, so a box drawn over a scanned page can still leave the words searchable.

Check it on every file you share. A document's title or author field can hold a name or case reference even when every page is clean.

How to check that a redacted PDF is really redacted

By RedactSnap · 20 October 2026

A black box on a page proves nothing about the file. Many redaction failures, including court filings in high-profile cases, were black rectangles drawn over text that was still in the PDF. These five tests take two minutes and catch most of them.

Five tests to run on the file you will send

Run them on the exact file you are about to send, opened fresh, not on the copy in your editor.

Step 1: Search. Open the PDF and search (Ctrl+F or Cmd+F) for a word or number you hid. If it is found, it is still in the file.
Step 2: Select and copy. Drag across a black box, copy, and paste into a plain text editor. If text appears, the box is only on top.
Step 3: Select all. Press Ctrl+A or Cmd+A on each page and paste into a text editor. This catches hidden text, text under images, and white text on a white background.
Step 4: Check the document properties (File > Properties or Document Properties). Author, title, subject and keywords can carry names, case numbers or file paths.
Step 5: Look at the edges. Check headers, footers, page margins, bookmarks, comments, form fields and attachments, which a page-by-page review can miss. Zoom in on each box to check that no part of a letter shows.

If a test fails

Don't patch the file. Go back to the original and redact it with a tool that removes the content: Adobe Acrobat's Redact tool, Preview's Redact tool on a Mac, or a tool that flattens each page to an image.

RedactSnap flattens every page on export, so a flattened PDF has no text layer for the search and copy tests to find. It runs the same checks on the exported file before you download it: selectable text, the words you redacted, and metadata.

RedactSnap's Check and download screen: selectable text removed, no redacted words found in the file data, metadata removed

Try it on your own file

The tool opens PDFs, PNGs and JPGs in your browser. The file is not uploaded.

Redact a PDF or image