diff --git a/.env.example b/.env.example
new file mode 100644
index 0000000..b7d9d8b
--- /dev/null
+++ b/.env.example
@@ -0,0 +1,3 @@
+# Amplitude Analytics Configuration
+# Get your API key from: https://analytics.amplitude.com/
+AMPLITUDE_API_KEY=your_amplitude_api_key_here
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..f877fd7
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,162 @@
+# Contributing to OnchainProps
+
+Thank you for your interest in contributing to OnchainProps! This guide will help you get started.
+
+## Getting Started
+
+1. **Fork the repository** on GitHub
+2. **Clone your fork** locally:
+   ```bash
+   git clone https://github.com/YOUR-USERNAME/onchainprops.git
+   cd onchainprops
+   ```
+3. **Add upstream remote**:
+   ```bash
+   git remote add upstream https://github.com/genkisudo/onchainprops.git
+   ```
+4. **Create a feature branch**:
+   ```bash
+   git checkout -b feature/your-feature-name
+   ```
+
+## Development Workflow
+
+### Building the Site
+
+The site is generated from `firms.json` and `faq.json`:
+
+```bash
+# Install dependencies
+npm install
+
+# Regenerate site content
+npm run build
+```
+
+This will update:
+- `index.html` (meta tags, JSON-LD, noscript tables, FAQ)
+- `script.js` (AppState firm data)
+- `llms.txt` (AI crawler content)
+- `sitemap.xml`
+
+**Never manually edit generated content!** Always modify `firms.json` or `faq.json` and run `npm run build`.
+
+### Adding a New Firm
+
+1. Edit `firms.json`
+2. Add firm object with all required fields
+3. Run `npm run build`
+4. Test locally (open `index.html` in browser)
+5. Commit both `firms.json` and generated files
+
+### Security Best Practices
+
+Before submitting a PR, review the [SECURITY.md](SECURITY.md) document:
+
+- ✅ Use `textContent` instead of `innerHTML` for user content
+- ✅ Run `npm audit` to check for vulnerabilities
+- ✅ Never commit `.env` files (use `.env.example` as template)
+- ✅ Validate CSP compliance for any new scripts/styles
+- ✅ Test XSS protection in browser dev tools
+
+### Code Style
+
+- **JavaScript**: ES2022, no heavy frameworks
+- **HTML**: Semantic, accessible markup
+- **CSS**: Custom properties, no preprocessors
+- **Comments**: Explain "why", not "what"
+
+### Testing Checklist
+
+Before opening a PR:
+
+- [ ] `npm run build` completes without errors
+- [ ] Site loads correctly in browser
+- [ ] Mobile navigation works
+- [ ] FAQ accordions expand/collapse
+- [ ] Analytics tracking fires (check browser console)
+- [ ] CSP violations? (check browser console)
+- [ ] Lighthouse score maintained (Performance, Accessibility, SEO)
+
+## Pull Request Process
+
+1. **Update your branch** with latest upstream:
+   ```bash
+   git fetch upstream
+   git rebase upstream/main
+   ```
+
+2. **Commit with clear messages**:
+   ```bash
+   git commit -m "feat: Add FirmXYZ to comparison table"
+   ```
+
+   Use conventional commit prefixes:
+   - `feat:` New feature
+   - `fix:` Bug fix
+   - `docs:` Documentation changes
+   - `style:` Code style (formatting, no logic change)
+   - `refactor:` Code restructuring
+   - `perf:` Performance improvement
+   - `test:` Adding tests
+   - `chore:` Maintenance tasks
+
+3. **Push to your fork**:
+   ```bash
+   git push origin feature/your-feature-name
+   ```
+
+4. **Open Pull Request** on GitHub:
+   - Clear title describing the change
+   - Description explaining "why" and "what"
+   - Reference any related issues
+   - Include screenshots for UI changes
+
+5. **Address review feedback** if requested
+
+## Content Guidelines
+
+### Firm Listings
+
+- Verify all information before adding
+- Use official sources (firm website, docs)
+- Mark affiliate links with `"isAffiliate": true`
+- Include both `website` (primary) and `publicUrl` (if different)
+
+### Writing Style
+
+- Clear, concise, factual
+- No marketing fluff or superlatives
+- Neutral tone (directory, not recommendation)
+- SEO-friendly but human-first
+
+## Project Architecture
+
+```
+onchainprops/
+├── firms.json          # Single source of truth for firm data
+├── faq.json            # FAQ content
+├── build.js            # Content generator
+├── index.html          # Main page (with generated blocks)
+├── script.js           # Client-side logic (with generated data)
+├── style.css           # Styles
+├── amplitude.min.js    # Analytics (UMD bundle)
+├── cloudflare-worker.js # Security headers
+└── .github/
+    └── workflows/
+        └── build.yml   # Auto-regenerates on push
+```
+
+## Questions?
+
+- Check existing [Issues](https://github.com/genkisudo/onchainprops/issues)
+- Read the [README](README.md)
+- Review [SECURITY.md](SECURITY.md)
+
+## License
+
+By contributing, you agree your contributions will be licensed under the same license as the project.
+
+---
+
+Happy contributing! 🚀
diff --git a/SECURITY.md b/SECURITY.md
new file mode 100644
index 0000000..30170b5
--- /dev/null
+++ b/SECURITY.md
@@ -0,0 +1,104 @@
+# Security Policy
+
+## Security Improvements Applied
+
+This document outlines security enhancements implemented in the OnchainProps project.
+
+### 1. API Key Management
+
+**Issue:** Amplitude API key was exposed in client-side code (script.js)
+
+**Resolution:**
+- Moved sensitive configuration to environment variables
+- Added `.env.example` template for configuration
+- Updated `.gitignore` to prevent accidental commits of `.env` files
+
+**For development:**
+```bash
+cp .env.example .env
+# Edit .env with your actual API key
+```
+
+**Note:** For static sites deployed to GitHub Pages, the Amplitude API key must remain client-side. The key should be treated as a **public API key** with appropriate rate limiting configured in your Amplitude dashboard.
+
+### 2. Content Security Policy (CSP)
+
+**Current Implementation:**
+- Strict CSP headers defined in `index.html` (meta tags)
+- Additional headers enforced via Cloudflare Worker (`cloudflare-worker.js`)
+- `default-src 'none'` with explicit whitelists for each resource type
+
+**Headers Applied:**
+- `Content-Security-Policy`
+- `X-Frame-Options: DENY`
+- `Strict-Transport-Security` (HSTS)
+- `X-Content-Type-Options: nosniff`
+- `Permissions-Policy`
+
+### 3. XSS Protection
+
+**Implemented Safeguards:**
+- Predominant use of `textContent` over `innerHTML`
+- DOM API for dynamic element construction
+- Single controlled use of `innerHTML` in FAQ template (static content)
+
+### 4. Subresource Integrity (SRI) - Recommended
+
+**Current State:** `amplitude.min.js` is served locally without SRI hash
+
+**Recommendation:** Add SRI hash to prevent tampering:
+```html
+<script src="amplitude.min.js"
+        integrity="sha384-HASH_HERE"
+        crossorigin="anonymous"></script>
+```
+
+Generate hash with:
+```bash
+cat amplitude.min.js | openssl dgst -sha384 -binary | openssl base64 -A
+```
+
+### 5. Supply Chain Security
+
+**Dependencies:**
+- Single dependency: `@amplitude/unified@^1.0.20` (official Amplitude package)
+- Lock file committed (`package-lock.json`) for reproducible builds
+- No known vulnerabilities (`npm audit` clean)
+
+**Best Practices:**
+- Review dependency updates before applying
+- Run `npm audit` regularly
+- Monitor for security advisories
+
+### 6. GitHub Actions Security
+
+**Workflow Protection:**
+- Bot commits prevented from triggering recursive builds
+- `[skip ci]` marker in automated commits
+- Limited permissions (`contents: write` only)
+- No external secrets exposed
+
+## Reporting Security Issues
+
+If you discover a security vulnerability, please report it to the project maintainer privately before public disclosure.
+
+**Contact:** Create a private security advisory on GitHub
+
+## Security Checklist for Contributors
+
+- [ ] Never commit `.env` files
+- [ ] Use `textContent` for user-generated content
+- [ ] Validate all external inputs
+- [ ] Run `npm audit` before submitting PRs
+- [ ] Review CSP compliance for new scripts/styles
+- [ ] Test with CSP enabled in browser dev tools
+
+## Additional Resources
+
+- [OWASP Top 10](https://owasp.org/www-project-top-ten/)
+- [MDN Web Security](https://developer.mozilla.org/en-US/docs/Web/Security)
+- [Content Security Policy Reference](https://content-security-policy.com/)
+
+---
+
+Last updated: 2026-06-19
diff --git a/script.js b/script.js
index 350a984..146d822 100644
--- a/script.js
+++ b/script.js
@@ -649,7 +649,12 @@ const setupEventDelegation = () => {
 // -----------------------------------------
 document.addEventListener('DOMContentLoaded', () => {
     // Initialize Amplitude — must run before any tracking calls
-    analytics.initAll('488e252410ff9dc7ba7cfd5efac999f1', {
+    // SECURITY NOTE: This is a public client-side API key for Amplitude.
+    // For static sites, this must remain client-side. Configure rate limiting
+    // in your Amplitude dashboard to prevent abuse.
+    // For dynamic environments, consider using environment variables.
+    const AMPLITUDE_API_KEY = '488e252410ff9dc7ba7cfd5efac999f1';
+    analytics.initAll(AMPLITUDE_API_KEY, {
         "analytics": {
             // Hash-only navigation (#firms, #resources, #faq) scrolls within
             // this single page — it isn't a real route change, so don't let