🛡️ PromptShield

A privacy-focused browser extension that detects and redacts PII (Personally Identifiable Information) before you send prompts to AI chat services.

✨ Features

Comprehensive PII Detection

• 📧 Email addresses - john.doe@example.com
• 📱 Phone numbers - (555) 123-4567, +1-555-123-4567
• 💳 Credit cards - 4532-1488-0343-6467
• 🔐 SSN - 123-45-6789
• 🌐 IP addresses - 192.168.1.1
• 🔑 API keys - sk_live_abc123, AWS keys, JWT tokens
• 🔗 URLs - https://example.com
• 📅 Dates/Birthdays - 15th August, 08/15/2005
• 📍 Addresses - New York NY 10001
• 🏠 Street addresses - 123 Main Street
• 👤 Names (optional) - Detects names with context ("my name is...")

Smart Detection

• Context-aware name detection - Catches names after phrases like "my name is", "I'm", "called"
• Works on modern chat UIs - Claude.ai, ChatGPT, Gemini, and more
• Real-time interception - Blocks send until you review and approve
• Flexible redaction styles - Generic, numbered, or hashed placeholders

🚀 Installation

Development Install

1. Clone and build:

   git clone https://github.com/YOUR_USERNAME/PromptShield.git
   cd PromptShield
   npm install
   npm run build

2. Load in Chrome:

   • Open chrome://extensions/
   • Enable "Developer mode" (top right)
   • Click "Load unpacked"
   • Select the dist/ folder

Configuration

Click the extension icon to configure:

• ✅ Detect names - Enable heuristic name detection
• 🎨 Redaction style - Choose how PII is replaced
  • Generic: [EMAIL]
  • Numbered: [EMAIL_1], [EMAIL_2]
  • Hashed: [EMAIL_a1b2c3]
• 👁️ Auto-preview - Show modal when PII detected

🎯 How It Works

1. You type a message in any chat interface
2. Click "Send" or press Cmd/Ctrl+Enter
3. PromptShield intercepts if PII is detected
4. Review modal appears showing:
   • Original text
   • Redacted version
   • Redaction map
5. Choose your action:
   • ✅ Send Redacted - Safe version sent
   • ⚠️ Send Original - Keep PII (not recommended)
   • ❌ Cancel - Don't send anything

🏗️ Architecture

src/
├── background.ts        # Service worker
├── contentScript.ts     # Injection & interception logic
├── detector-core.ts     # PII detection patterns
├── detector.ts          # Detector API
└── popup.ts            # Extension popup UI

build.js                # esbuild bundler
manifest.json           # Extension manifest

🧪 Development

Build

npm run build

Test

npm test

Project Structure

• Source TypeScript files in src/
• Build output in dist/ (gitignored)
• Uses esbuild for fast bundling

📝 Future Enhancements

• Machine learning-based entity detection (NER)
• Per-site customization and allow-lists
• Export/import redaction history
• Support for more PII types (driver's license, passport, etc.)
• Privacy-preserving analytics

🤝 Contributing

Contributions welcome! Please feel free to submit a Pull Request.

🛠️ Development Tools

Built with assistance from Claude Code - an AI-powered development tool.

📄 License

MIT License - See LICENSE file for details

⚠️ Disclaimer

This is a prototype. While it detects many common PII patterns, it may not catch everything. Always review your prompts before sending sensitive information.