Silent Send

A Chrome extension that intercepts personal information and substitutes it with user-defined replacements before sending to Claude.ai.

How it works

1. You define mappings — e.g. "John Smith" → "Alex Demo", "john@gmail.com" → "alex@example.com"
2. You type normally — you see your real text while composing
3. On send, it swaps — the extension intercepts the API request and replaces real values with substitutes
4. Badge shows count — the extension icon shows how many substitutions were made
5. Reveal mode — optionally translates Claude's responses back to your real data

How to verify it's working

• Badge count on the extension icon shows substitutions per page
• Activity tab in the popup shows a timestamped log of every substitution
• Test tab in the popup lets you type text and see the before/after diff
• Reveal mode (eye icon) toggles showing real vs substitute data in responses
• Browser DevTools → Console shows [Silent Send] Substituted N value(s) messages

Installation

Chrome (Developer Mode)

1. Clone this repo
2. Run ./build.sh chrome (or just use the root directory directly)
3. Open chrome://extensions/
4. Enable Developer mode (top right)
5. Click Load unpacked → select dist/chrome/ (or root dir)
6. Navigate to claude.ai — the extension is active

Firefox (signed, persistent)

1. Clone this repo
2. npm install
3. Get your free Mozilla API credentials at https://addons.mozilla.org/developers/addon/api/key/
4. cp .env.example .env and fill in your key + secret
5. source .env && npm run sign:firefox
6. Install the .xpi file from dist/firefox-signed/ — drag it into Firefox or use File → Open
7. Navigate to claude.ai — the extension is active

The signed .xpi is permanent — survives restarts, no store listing needed.

Firefox (temporary, for development)

npm install && npm run run:firefox

Opens Firefox with the extension pre-loaded. Reloads on file changes.

No store required for either browser.

Architecture

manifest.json           — Extension manifest (Manifest V3)
src/
  background/
    service-worker.js   — Badge management, logging coordination
  content/
    injector.js         — Content script (isolated world) — loads config, bridges messaging
    content.js          — Page script (main world) — hooks fetch(), does substitution
    content.css         — Visual indicators (highlights, reveals)
  popup/
    popup.html/css/js   — Quick access: add mappings, view activity, test mode
  options/
    options.html/css/js — Full mapping management, import/export, settings
  lib/
    substitution-engine.js — Core find/replace logic
    storage.js          — Browser storage wrapper
    browser-polyfill.js — Chrome/Firefox API compatibility

Privacy

• All data stays local in browser storage
• No external servers, no telemetry, no analytics
• The extension only activates on claude.ai