Excel PII Masker

Detect PII in spreadsheet columns and mask it locally. No upload, no network.

Excel PII Masker finds personal information in your files and replaces it with consistent placeholders, so you can share a spreadsheet, document or deck — with a colleague, a vendor, or an AI assistant — without handing over the data underneath. Everything happens on your computer. There is no server, no account, and no network request of any kind. HOW IT WORKS 1. Open a file in the side panel: .xlsx, .csv, .docx or .pptx. 2. The extension scans it and shows you what it found — email addresses, phone numbers, names, PAN and GSTIN numbers, card numbers, company names, and identifier formats specific to your own data. 3. You choose what to mask. Confident detections are pre-selected; everything else is offered rather than assumed. 4. Download the masked file, or attach it directly to an open Claude or ChatGPT tab. 5. When the file or the answer comes back, restore the real values. MASKED VALUES STAY USEFUL Placeholders keep the shape of what they replaced and name the column they came from, so the file still reads as data: INV-2024-8831 becomes INV-2473-1347 ABCDE1234F becomes PANNO9158R Jane Kapoor becomes CUSTOMERNAME_206043 The same value always produces the same placeholder, so whoever receives the file can still group, filter, count and join on it. They simply cannot see who or what any row refers to. IT TELLS YOU WHAT IT IS UNSURE ABOUT A column of four region names is offered but not pre-selected, because masking it hides nothing and breaks the recipient's filters. A 16-digit order number is not reported as a card number, because the checksum does not match. Values that broke a column's pattern are shown so you can look at them. WORD AND POWERPOINT Documents are masked in place: formatting, images, tables and layout are untouched, and headers, footers, footnotes and speaker notes are scanned too — which is exactly where a stray account number usually survives. Documents find less than spreadsheets, deliberately. A spreadsheet column gives the detector hundreds of similar values to reason about; a paragraph does not. In documents only patterns that can be verified are reported — a checksum, or a format distinctive enough to stand alone. Person and company names are not detected in prose, because doing so reliably is not possible and a wrong answer would be worse than none. WORKING WITH CLAUDE AND CHATGPT (OPTIONAL) With your permission, the extension can attach a masked file straight to an open chat tab, restore the real values inside an answer on that page, and offer to unmask a file the model sends back. This access is optional and off by default. It is requested at the moment you use one of those buttons, covers claude.ai and chatgpt.com only, and can be revoked at any time. Decline it and everything else works unchanged. REVERSIBLE, LOCALLY The values behind each placeholder are encrypted on your machine with a key derived from a passphrase you choose. When a masked file comes back — renamed, reordered, rows added or removed — the extension restores it without asking you to map anything. You can also paste an assistant's reply in and get the real values back. PRIVACY - No server, no account, no analytics, no telemetry - Your file is never written to disk and never leaves your computer - Stored values are encrypted with AES-256-GCM; keys are derived with PBKDF2 (600,000 iterations) and held non-extractably by the browser - The extension has no access to any website until you grant it, for two sites, at the moment you use the feature Your passphrase is never stored and cannot be recovered. If you lose it, masked files can no longer be reversed — by you or by anyone else.