hddn Hide what matters.

Local PDF redaction

Redact PDFs without letting them leave your device.

hddn runs entirely in your browser. Open a PDF and it flags names, IDs, and other sensitive details for you to confirm. Black out any text or area yourself, or edit the wording when the file is digital. Then export a clean copy. Nothing is uploaded, and it keeps working with your Wi-Fi off.

Redact a PDFVerify the privacy claim

Processed locally in your browser. No uploads, no account.

WI-FI OFF · OKoffer-letter.pdfOpenedEmployment offerREF HR-2026-0418 · 12 MAR 2026Dear Maria Kowalski,We are pleased to offer you the role of SeniorAnalyst from 1 April 2026, at an annual salaryof €68,400, paid monthly to the accountLT60 1010 0123 4567 8910.Please sign and return this letter by email tom.kowalski@proton.me or call us on+370 612 34567 with any questions.Maria KowalskiACCEPTED BYNAMECONFIRMSALARYCONFIRMIBANCONFIRMEMAILCONFIRMPHONECONFIRMNAMECONFIRMprocessed locallyExportSaved to your device · 0 bytes uploaded

Prove it yourself

Don't take our word for it. Turn off your Wi-Fi.

The privacy claim isn't a promise you have to trust. It's a property you can check on your own machine in under a minute.

Run the offline test

Offline test

Under a minute

  1. 01

    Open the redaction tool

  2. 02

    Click "Load offline tools"

  3. 03

    Turn on airplane mode

  4. 04

    Refresh the page

  5. 05

    Open and redact a PDF, fully disconnected

How it works

Four steps. You stay in charge of every one.

  1. 01

    Open your PDF

    Drop the file onto the page. Your browser opens it right on your device.

  2. 02

    We mark candidates

    Names, emails, IDs, account numbers, and dates that may need to be hidden get highlighted.

  3. 03

    You review everything

    Confirm the marks, reject the ones you disagree with, or add your own by blacking out any text or area. On digital PDFs you can even edit the words. Nothing is hidden until you approve it.

  4. 04

    Export a clean PDF

    The confirmed data is permanently removed, not just covered, and saved back to your device.

Who it's for

For documents that can't afford a leak.

  • Legal

    Before filing or discovery

    Strip client names, case details, and identifiers from briefs and exhibits before they circulate.

  • HR & People

    Before sharing personnel files

    Share contracts, reviews, and offer letters without exposing salaries or personal data.

  • Finance

    Before statements go out

    Remove account numbers, IBANs, and balances from statements, invoices, and reports.

Privacy, plainly

What happens to your document, and what doesn't.

  • Your PDF is processed entirely in your browser. No processing server exists.
  • Nothing is uploaded, stored remotely, or shared with third parties.
  • Offline mode caches app tooling only, never your files or their contents.
  • The exported PDF is saved directly back to your device.

Current scope

PDF

files only

25 MB

per file

30

pages max

Detection is assistive, not perfect. Nothing is redacted until you approve it, and you review every suggestion before export.

Before you send it

What actually goes wrong with redaction.

Short, practical reads: why covered text stays in the file, what GDPR expects you to remove, how to redact a scan, and how careful organisations still got it wrong.

Read the guides
  1. 01A black rectangle is not redactionWhy the text survives underneath, and the ten-second test that catches it.
  2. 02How to redact a PDF for GDPRWho counts as identifiable, and why uploading the file is its own problem.
  3. 03Three redaction failures worth studyingThe Pentagon, the TSA, and a legal team all shipped the same mistake.
  4. 04How to redact a PDF and know it workedThe whole sequence in order, including the check almost nobody runs.
  5. 05How to redact a PDF without uploading itTwo checks that tell you where your file is really being processed.
  6. 06How to remove text from a PDF permanentlyFixing a wrong figure and hiding a sensitive one need different tools.
  7. 07How to redact a scanned PDFWhy the black box can work here, and the invisible text layer that ruins it.

Questions

Fair questions, straight answers.

All questions
01Is my document uploaded anywhere?

No. The PDF is opened and processed by your own browser, on your own device. There is no processing server, and the file never leaves your machine. You can verify this by disconnecting from the internet and continuing to work.

02How does offline mode work?

While connected, the tool downloads its own processing code into your browser cache. After that you can switch to airplane mode, refresh the page, and keep redacting. Only the app tooling is cached, never your files.

03What does it detect?

Names, emails, phone numbers, URLs, addresses, dates, IBANs, card-like numbers, IDs, and any keywords you add. Detection is rule-based and assistive: it marks candidates, and you decide what gets removed. You can also black out any text or draw a box over any area yourself.

04Can I edit the text in a PDF, not just hide it?

Yes, if the PDF is digital, meaning the text can be selected rather than being a scan or photo. You can fix a name, change a number, or delete a line, and the edit is saved into the file you export. Scanned pages can be redacted but not retyped.

05Is the redaction permanent?

Yes. Exported redactions are true redactions: the underlying text is removed from the PDF, not just covered with a black box. If a document is malformed, a flattened fallback export is used instead.

06What does it cost?

Nothing. There is no account, no trial, and no payment step.

Clean it up before it leaves your hands.

Free to use. No account, no upload, no payment step.

Redact a PDF