Redaction Checker

What is a redaction checker?

A redaction checker is a tool that tests a redacted PDF for information that is still in the file. A PDF can look correctly redacted on the screen and still contain the text under each black bar. Anyone who selects that text, copies it or opens the file in another app can read it.

The Redaction Checker compares what the page shows with what the file contains. When a word is in the file but cannot be seen on the page, the checker reports it as a leak.

Why use a redaction checker tool?

Bad redaction is a common mistake. People draw black boxes in a PDF editor or a word processor, or they mark text for redaction and forget to apply it. The result looks correct, so the mistake is often found only after the file is shared, sometimes by a journalist or by the other side in a court case.

A checker finds these problems before you send the file. It is also useful when you receive a redacted PDF and want to know if it is safe to pass on, or when you must confirm that redaction by another person or another tool worked.

How does the Redaction Checker work?

1. Choose a PDF or drop it on the page. You can also click "Try a badly redacted example".
2. Wait for the check. The tool reads each page and shows its progress.
3. Read the findings. Leaks show first, then points to check. Click a page number to go to that page, where each leak is marked.
4. Download the report as a .txt file if you need a record.
5. Fix any leak with the PDF Redactor, then check the new file again.

To find text under bars, the tool draws each page as an image and looks at the pixels behind every word in the text layer. If the area behind a word is one flat color, the word cannot be seen. A dark color means the word is under a black bar. A light color means white text, or text under a white box. The tool also reads the file's annotations, metadata and attachments, and counts how many times the file was saved over.

Is my PDF safe?

Yes. Most online tools upload your file to a server. This one does not. The page has no server code and uses no AI model: PDF.js reads the PDF and draws the pages in your browser, and your file never leaves your device. The checker only reads your PDF. It does not change it. Read our privacy policy for the details.

What can the Redaction Checker find?

• Text under black bars that is covered on the page but still in the file
• Hidden text, such as white text or text under a white box
• Redactions marked but not applied, where the text under the mark is still in the file
• Text outside the page, which is in the file but outside the visible area
• Earlier versions saved inside the file, and old titles or author names from them
• Comments and notes, which often contain names
• Form fields with values
• Attached files inside the PDF
• Metadata, such as the title, author, the app that made the file, and the dates it was made and changed

The checker does not read text inside images. On a scanned page, a black bar drawn over the image is part of the image, so there is no text under it to find.

Who uses a redaction checker?

• Lawyers and paralegals who must confirm that court filings and disclosure documents do not leak privileged details.
• Public sector staff who check documents before they publish them or answer freedom of information requests.
• Journalists who check documents they receive, and protect sources in documents they publish.
• Compliance and privacy teams who check files before they leave the company.
• Anyone who received a redacted PDF and wants to know what is still in it before they pass it on.

Redaction Checker vs. checking a PDF by hand

To check a redacted PDF by hand, you select the text under each bar, copy it into another app, and look through the document properties, comments and attachments. This works for one page, but it is easy to miss white text, text outside the page or an earlier version saved in the file.

The Redaction Checker runs all of these checks on every page at once and marks each leak on the page. If it finds a leak, use the PDF Redactor to make a new PDF from images of the pages, so no text, earlier versions or metadata stay in it. To remove only the metadata from a PDF, a photo or a video, use the Metadata Stripper.