Why Real Redaction Means Flattening
A black rectangle drawn on top of a PDF is not redaction. If the underlying text is still in the file, anyone can select it, copy it, or remove the box and read what was beneath β a mistake that has exposed confidential data in countless leaked documents. True redaction has to destroy the underlying content, not merely hide it visually.
This tool does it the safe way: after you mark the areas to hide, every page is rasterised to an image, the black boxes are painted onto that image, and a fresh PDF is built from the flattened result. There is no text layer left underneath the marks β the words, numbers and any selectable data in those regions no longer exist in the output file.
Private by Design
Because the entire process β rendering, painting the boxes and rebuilding the PDF β runs in your browser, the sensitive document is never transmitted anywhere. That matters most precisely for the kind of file you would redact. The only network traffic is the one-time download of the open-source rendering library.