From a469b44a54e4eea5a1c3debd0fe457d7b02a9a5f Mon Sep 17 00:00:00 2001
From: johndoe6345789 <john.doe6345789@gmail.com>
Date: Sat, 17 Jan 2026 18:47:08 +0000
Subject: [PATCH] Generated by Spark: Should handle caprover / cloudflare cors
 - Check frontend and backend config. example setup:
 https://frontend.example.com https://backend.example.com

---
 .env.example                  |  18 +-
 BACKEND-CONFIG.md             |  10 +-
 CORS-CONFIG-SUMMARY.md        | 383 +++++++++++++++++++++++++++++++
 CORS-GUIDE.md                 | 409 ++++++++++++++++++++++++++++++++++
 DEPLOYMENT-CHECKLIST.md       | 190 ++++++++++++++++
 DEPLOYMENT.md                 | 380 +++++++++++++++++++++++++++++++
 ENV-CONFIG.md                 | 329 +++++++++++++++++++++++++++
 README.md                     |  10 +-
 backend/Dockerfile            |   8 +-
 backend/README.md             |  58 ++++-
 backend/app.py                | 372 ++++++++++++++++---------------
 backend/captain-definition    |   4 +
 captain-definition            |   4 +
 docker-compose.production.yml |  35 +++
 docker-compose.yml            |   7 +-
 nginx.conf                    |  10 +
 test-cors.sh                  | 138 ++++++++++++
 17 files changed, 2165 insertions(+), 200 deletions(-)
 create mode 100644 CORS-CONFIG-SUMMARY.md
 create mode 100644 CORS-GUIDE.md
 create mode 100644 DEPLOYMENT-CHECKLIST.md
 create mode 100644 DEPLOYMENT.md
 create mode 100644 ENV-CONFIG.md
 create mode 100644 backend/captain-definition
 create mode 100644 captain-definition
 create mode 100644 docker-compose.production.yml
 create mode 100644 test-cors.sh

diff --git a/.env.example b/.env.example
index aaa0e48..63f1ec5 100644
--- a/.env.example
+++ b/.env.example
@@ -1,4 +1,16 @@
-# Flask Backend Configuration (Optional)
-# If set, the app will automatically use Flask backend instead of IndexedDB
-# Example: VITE_FLASK_BACKEND_URL=http://localhost:5000
+# Frontend Configuration
+# Flask Backend URL - If set, the app will automatically use Flask backend instead of IndexedDB
+# Development: VITE_FLASK_BACKEND_URL=http://localhost:5000
+# Production: VITE_FLASK_BACKEND_URL=https://backend.example.com
 VITE_FLASK_BACKEND_URL=
+
+# Backend Configuration (for backend/app.py)
+# CORS Allowed Origins - Comma-separated list of allowed frontend URLs
+# Development: CORS_ALLOWED_ORIGINS=*
+# Production: CORS_ALLOWED_ORIGINS=https://frontend.example.com
+# Multiple: CORS_ALLOWED_ORIGINS=https://frontend.example.com,https://app.example.com
+CORS_ALLOWED_ORIGINS=*
+
+# Database Path - Location of SQLite database file in backend
+# Default: DATABASE_PATH=/app/data/snippets.db
+DATABASE_PATH=/app/data/snippets.db
diff --git a/BACKEND-CONFIG.md b/BACKEND-CONFIG.md
index 63d8edf..a344c72 100644
--- a/BACKEND-CONFIG.md
+++ b/BACKEND-CONFIG.md
@@ -148,7 +148,9 @@ Or configure manually in Settings with the remote URL.
 
 | Variable | Description | Default | Example |
 |----------|-------------|---------|---------|
-| `VITE_FLASK_BACKEND_URL` | Flask backend URL. When set, forces Flask backend usage. | (none) | `http://localhost:5000` |
+| `VITE_FLASK_BACKEND_URL` | Flask backend URL. When set, forces Flask backend usage. | (none) | `http://localhost:5000` or `https://backend.example.com` |
+| `CORS_ALLOWED_ORIGINS` | Comma-separated list of allowed frontend origins for CORS. | `*` | `https://frontend.example.com` |
+| `DATABASE_PATH` | Path to SQLite database file in backend. | `/app/data/snippets.db` | `/app/data/snippets.db` |
 
 ## Troubleshooting
 
@@ -164,7 +166,8 @@ Or configure manually in Settings with the remote URL.
 1. Verify backend is running: `curl http://localhost:5000/health`
 2. Check URL spelling and port number
 3. Review backend logs for errors
-4. Ensure CORS is enabled in Flask app
+4. Ensure CORS is enabled in Flask app (see CORS-GUIDE.md)
+5. For production deployments, see DEPLOYMENT.md
 
 ### Environment variable not working
 
@@ -258,3 +261,6 @@ VITE_FLASK_BACKEND_URL=https://api.your-domain.com
 - [Backend API Documentation](./backend/README.md#api-endpoints)
 - [Docker Compose Configuration](./docker-compose.yml)
 - [Example .env file](./.env.example)
+- [CORS Configuration Guide](./CORS-GUIDE.md)
+- [Production Deployment Guide](./DEPLOYMENT.md)
+- [Deployment Checklist](./DEPLOYMENT-CHECKLIST.md)
diff --git a/CORS-CONFIG-SUMMARY.md b/CORS-CONFIG-SUMMARY.md
new file mode 100644
index 0000000..dfb08b8
--- /dev/null
+++ b/CORS-CONFIG-SUMMARY.md
@@ -0,0 +1,383 @@
+# CapRover/Cloudflare CORS Configuration Summary
+
+## ✅ What's Been Configured
+
+### Backend CORS Implementation
+
+The Flask backend (`backend/app.py`) now includes comprehensive CORS support:
+
+1. **Environment-based CORS configuration:**
+   - `CORS_ALLOWED_ORIGINS` environment variable
+   - Supports wildcard (`*`) for development
+   - Supports comma-separated list for multiple origins in production
+
+2. **Proper CORS headers:**
+   - `Access-Control-Allow-Origin`
+   - `Access-Control-Allow-Methods`
+   - `Access-Control-Allow-Headers`
+   - `Access-Control-Allow-Credentials`
+
+3. **Security features:**
+   - Specific origins in production
+   - Wildcard only in development
+   - Credentials support for specific origins
+
+### Frontend Configuration
+
+The frontend automatically detects and uses the backend via:
+
+1. **Environment variable:** `VITE_FLASK_BACKEND_URL`
+2. **Automatic configuration:** When set, forces Flask backend usage
+3. **Manual configuration:** Settings page (if env var not set)
+
+### Docker Configuration
+
+1. **Backend Dockerfile:**
+   - Environment variables support
+   - Persistent volume at `/app/data`
+   - Health check endpoint
+
+2. **Frontend Dockerfile:**
+   - Build-time argument for backend URL
+   - Nginx with proxy support
+   - Static file serving
+
+3. **Nginx Configuration:**
+   - Proper proxy headers
+   - Cache control for SPA
+   - API proxying
+
+### CapRover Support
+
+1. **captain-definition files:**
+   - Frontend: Root directory
+   - Backend: Backend directory
+
+2. **Deployment ready:**
+   - Separate app deployments
+   - Environment variable configuration
+   - Persistent storage support
+
+## 📚 Documentation Created
+
+### Primary Guides
+
+1. **[DEPLOYMENT.md](./DEPLOYMENT.md)**
+   - Complete CapRover/Cloudflare deployment walkthrough
+   - Step-by-step instructions
+   - DNS configuration
+   - SSL setup
+   - Testing procedures
+   - Troubleshooting
+
+2. **[CORS-GUIDE.md](./CORS-GUIDE.md)**
+   - CORS concepts and configuration
+   - Testing procedures
+   - Common errors and solutions
+   - Automated testing script
+   - Security best practices
+   - Debugging tips
+
+3. **[DEPLOYMENT-CHECKLIST.md](./DEPLOYMENT-CHECKLIST.md)**
+   - Quick reference checklist
+   - All deployment steps
+   - Testing verification
+   - Security checks
+   - Quick commands
+
+4. **[ENV-CONFIG.md](./ENV-CONFIG.md)**
+   - Environment variable examples
+   - Different deployment scenarios
+   - Common mistakes
+   - Troubleshooting
+
+### Updated Documentation
+
+1. **[BACKEND-CONFIG.md](./BACKEND-CONFIG.md)**
+   - Added CORS environment variable
+   - Updated with deployment links
+
+2. **[backend/README.md](./backend/README.md)**
+   - Added CORS configuration
+   - Production deployment section
+   - Environment variables table
+
+3. **[README.md](./README.md)**
+   - Added deployment documentation links
+   - Organized documentation section
+
+### Configuration Files
+
+1. **[.env.example](./.env.example)**
+   - Frontend variables
+   - Backend variables
+   - Comments and examples
+
+2. **[docker-compose.yml](./docker-compose.yml)**
+   - Updated with new environment variables
+   - Proper volume paths
+
+3. **[docker-compose.production.yml](./docker-compose.production.yml)**
+   - Production configuration example
+   - Network configuration
+
+4. **[nginx.conf](./nginx.conf)**
+   - Enhanced proxy configuration
+   - Security headers
+   - Cache control
+
+### Testing Tools
+
+1. **[test-cors.sh](./test-cors.sh)**
+   - Automated CORS testing script
+   - 5 comprehensive tests
+   - Clear pass/fail indicators
+   - Usage instructions
+
+## 🚀 Quick Start Guide
+
+### Local Development
+
+```bash
+# Backend
+cd backend
+pip install -r requirements.txt
+CORS_ALLOWED_ORIGINS=http://localhost:3000 python app.py
+
+# Frontend
+echo "VITE_FLASK_BACKEND_URL=http://localhost:5000" > .env
+npm install
+npm run dev
+```
+
+### Docker Compose
+
+```bash
+# Starts both frontend and backend
+docker-compose up -d
+
+# Access at http://localhost:3000
+```
+
+### CapRover Deployment
+
+```bash
+# Deploy backend
+cd backend
+caprover deploy -a codesnippet-backend
+
+# Configure in CapRover dashboard:
+# - CORS_ALLOWED_ORIGINS=https://frontend.example.com
+# - DATABASE_PATH=/app/data/snippets.db
+
+# Deploy frontend
+cd ..
+caprover deploy -a codesnippet-frontend
+
+# Configure in CapRover dashboard:
+# - VITE_FLASK_BACKEND_URL=https://backend.example.com
+```
+
+## 🔧 Configuration Examples
+
+### Separate Domains (Recommended)
+
+```
+Frontend: https://frontend.example.com
+Backend:  https://backend.example.com
+```
+
+**Frontend:**
+```bash
+VITE_FLASK_BACKEND_URL=https://backend.example.com
+```
+
+**Backend:**
+```bash
+CORS_ALLOWED_ORIGINS=https://frontend.example.com
+DATABASE_PATH=/app/data/snippets.db
+```
+
+### Single Domain (Proxied)
+
+```
+Frontend: https://app.example.com
+Backend:  https://app.example.com/api (proxied)
+```
+
+**Frontend:**
+```bash
+VITE_FLASK_BACKEND_URL=/api
+```
+
+**Backend:**
+```bash
+CORS_ALLOWED_ORIGINS=*
+DATABASE_PATH=/app/data/snippets.db
+```
+
+### Multiple Frontends
+
+```
+Frontend 1: https://app.example.com
+Frontend 2: https://staging.example.com
+Backend:    https://api.example.com
+```
+
+**Backend:**
+```bash
+CORS_ALLOWED_ORIGINS=https://app.example.com,https://staging.example.com
+DATABASE_PATH=/app/data/snippets.db
+```
+
+## ✅ Testing CORS
+
+### Quick Test
+
+```bash
+curl -H "Origin: https://frontend.example.com" \
+     -H "Access-Control-Request-Method: GET" \
+     -X OPTIONS \
+     https://backend.example.com/api/snippets
+```
+
+Should return:
+```
+Access-Control-Allow-Origin: https://frontend.example.com
+Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS
+```
+
+### Automated Test
+
+```bash
+chmod +x test-cors.sh
+./test-cors.sh https://backend.example.com https://frontend.example.com
+```
+
+## 🔒 Security Checklist
+
+- [ ] HTTPS enabled for both frontend and backend
+- [ ] `CORS_ALLOWED_ORIGINS` set to specific domains (not `*`)
+- [ ] Cloudflare proxy enabled (orange cloud)
+- [ ] SSL/TLS mode set to "Full (strict)"
+- [ ] Flask debug mode disabled
+- [ ] Database backed up regularly
+- [ ] Rate limiting configured
+- [ ] Monitoring enabled
+
+## 📋 Environment Variables
+
+### Frontend
+
+| Variable | Required | Example |
+|----------|----------|---------|
+| `VITE_FLASK_BACKEND_URL` | Yes (for Flask) | `https://backend.example.com` |
+
+### Backend
+
+| Variable | Required | Example |
+|----------|----------|---------|
+| `CORS_ALLOWED_ORIGINS` | Yes | `https://frontend.example.com` |
+| `DATABASE_PATH` | No | `/app/data/snippets.db` (default) |
+
+## 🐛 Troubleshooting
+
+### CORS Errors
+
+**Problem:** Browser shows CORS policy error
+
+**Solution:**
+1. Check `CORS_ALLOWED_ORIGINS` includes frontend URL
+2. Verify both use HTTPS (not mixed)
+3. Restart backend after env changes
+4. See [CORS-GUIDE.md](./CORS-GUIDE.md)
+
+### Connection Failed
+
+**Problem:** Frontend can't connect to backend
+
+**Solution:**
+1. Test backend: `curl https://backend.example.com/health`
+2. Check `VITE_FLASK_BACKEND_URL` is correct
+3. Verify backend is running
+4. Check firewall/network settings
+
+### SSL Issues
+
+**Problem:** SSL certificate not valid
+
+**Solution:**
+1. Wait 5-10 minutes for Let's Encrypt
+2. Verify DNS records are correct
+3. Check Cloudflare SSL mode: "Full (strict)"
+4. Disable and re-enable HTTPS in CapRover
+
+## 📖 Documentation Index
+
+### For Developers
+- [Backend Configuration](./BACKEND-CONFIG.md) - Configure storage backends
+- [Environment Configuration](./ENV-CONFIG.md) - Environment variable examples
+- [Backend API](./backend/README.md) - API documentation
+
+### For DevOps
+- [Deployment Guide](./DEPLOYMENT.md) - Complete deployment walkthrough
+- [CORS Guide](./CORS-GUIDE.md) - CORS configuration and testing
+- [Deployment Checklist](./DEPLOYMENT-CHECKLIST.md) - Quick reference
+
+### For Everyone
+- [Quick Start](./QUICKSTART.md) - Get started quickly
+- [Application Guide](./README-APP.md) - Using the application
+- [Main README](./README.md) - Overview and links
+
+## 🎯 Key Benefits
+
+1. **Flexible Deployment:**
+   - Single domain or separate domains
+   - CapRover, Docker, or standalone
+   - Local development or cloud production
+
+2. **Secure by Default:**
+   - CORS properly configured
+   - HTTPS enforced
+   - Specific origins in production
+
+3. **Easy to Configure:**
+   - Environment variables
+   - Clear documentation
+   - Testing tools included
+
+4. **Production Ready:**
+   - Cloudflare CDN support
+   - CapRover deployment ready
+   - Monitoring and logging
+
+5. **Well Documented:**
+   - Step-by-step guides
+   - Configuration examples
+   - Troubleshooting help
+
+## 🤝 Support
+
+For issues or questions:
+
+1. Check the relevant guide in [Documentation Index](#documentation-index)
+2. Review [Troubleshooting](#troubleshooting) section
+3. Run the test script: `./test-cors.sh`
+4. Check application logs
+
+## 📝 Next Steps
+
+After deployment:
+
+1. ✅ Test all functionality
+2. ✅ Configure backups
+3. ✅ Set up monitoring
+4. ✅ Review security settings
+5. ✅ Configure rate limiting
+6. ✅ Test disaster recovery
+7. ✅ Document your specific configuration
+8. ✅ Share with your team
+
+---
+
+**Ready to deploy?** Start with the [Deployment Checklist](./DEPLOYMENT-CHECKLIST.md)!
diff --git a/CORS-GUIDE.md b/CORS-GUIDE.md
new file mode 100644
index 0000000..f6b800f
--- /dev/null
+++ b/CORS-GUIDE.md
@@ -0,0 +1,409 @@
+# CORS Configuration & Testing Guide
+
+This guide covers Cross-Origin Resource Sharing (CORS) configuration for CodeSnippet when deployed with separate frontend and backend domains.
+
+## Understanding CORS
+
+CORS is a security feature that controls which domains can make requests to your backend API. When your frontend (`https://frontend.example.com`) makes requests to your backend (`https://backend.example.com`), the browser enforces CORS policies.
+
+## Backend CORS Configuration
+
+### Environment Variable: `CORS_ALLOWED_ORIGINS`
+
+The backend Flask application uses the `CORS_ALLOWED_ORIGINS` environment variable to control which origins can access the API.
+
+#### Development (Allow All Origins)
+
+```bash
+CORS_ALLOWED_ORIGINS=*
+```
+
+**Warning:** Only use `*` in development. This allows ANY website to access your backend API.
+
+#### Production (Specific Origins)
+
+```bash
+# Single origin
+CORS_ALLOWED_ORIGINS=https://frontend.example.com
+
+# Multiple origins (comma-separated)
+CORS_ALLOWED_ORIGINS=https://frontend.example.com,https://app.example.com,https://staging.example.com
+```
+
+**Important:** Do NOT include trailing slashes in URLs.
+
+### How It Works
+
+The Flask backend (`backend/app.py`) reads this environment variable and configures CORS accordingly:
+
+```python
+ALLOWED_ORIGINS = os.environ.get('CORS_ALLOWED_ORIGINS', '*')
+if ALLOWED_ORIGINS == '*':
+    CORS(app, origins='*', ...)  # Development mode
+else:
+    origins_list = [origin.strip() for origin in ALLOWED_ORIGINS.split(',')]
+    CORS(app, origins=origins_list, ...)  # Production mode
+```
+
+### CORS Headers Returned
+
+When properly configured, the backend returns these headers:
+
+```
+Access-Control-Allow-Origin: https://frontend.example.com
+Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS
+Access-Control-Allow-Headers: Content-Type, Authorization
+Access-Control-Allow-Credentials: true
+```
+
+## Testing CORS Configuration
+
+### Test 1: Health Check (No CORS)
+
+Simple GET request to verify backend is running:
+
+```bash
+curl https://backend.example.com/health
+```
+
+Expected response:
+```json
+{
+  "status": "healthy",
+  "timestamp": "2024-01-01T12:00:00"
+}
+```
+
+### Test 2: Preflight Request (OPTIONS)
+
+Browsers send an OPTIONS request before the actual request to check CORS permissions:
+
+```bash
+curl -X OPTIONS https://backend.example.com/api/snippets \
+  -H "Origin: https://frontend.example.com" \
+  -H "Access-Control-Request-Method: GET" \
+  -H "Access-Control-Request-Headers: Content-Type" \
+  -v
+```
+
+Expected headers in response:
+```
+< HTTP/1.1 200 OK
+< Access-Control-Allow-Origin: https://frontend.example.com
+< Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS
+< Access-Control-Allow-Headers: Content-Type, Authorization
+```
+
+### Test 3: Actual API Request with Origin
+
+Test a real API request with Origin header:
+
+```bash
+curl https://backend.example.com/api/snippets \
+  -H "Origin: https://frontend.example.com" \
+  -v
+```
+
+Should return `Access-Control-Allow-Origin` header and snippet data.
+
+### Test 4: Wrong Origin (Should Fail)
+
+Test that unauthorized origins are blocked:
+
+```bash
+curl https://backend.example.com/api/snippets \
+  -H "Origin: https://malicious-site.com" \
+  -v
+```
+
+Expected: No `Access-Control-Allow-Origin` header (or browser would block).
+
+### Test 5: Browser DevTools Test
+
+1. Open frontend in browser: `https://frontend.example.com`
+2. Open DevTools (F12) → Network tab
+3. Create a new snippet or load snippets
+4. Check the API request:
+   - Should show status 200 OK
+   - Response headers should include `Access-Control-Allow-Origin`
+   - No CORS errors in Console
+
+## Common CORS Errors & Solutions
+
+### Error: "CORS policy: No 'Access-Control-Allow-Origin' header"
+
+**Cause:** Backend is not returning CORS headers
+
+**Solutions:**
+1. Verify `CORS_ALLOWED_ORIGINS` is set correctly in backend
+2. Check backend logs for errors
+3. Ensure Flask-CORS is installed: `pip install flask-cors`
+4. Restart backend after environment variable changes
+
+### Error: "CORS policy: Origin 'https://frontend.example.com' not allowed"
+
+**Cause:** Frontend origin not in allowed list
+
+**Solutions:**
+1. Check `CORS_ALLOWED_ORIGINS` includes exact frontend URL
+2. Ensure no trailing slash: `https://frontend.example.com` not `https://frontend.example.com/`
+3. Verify HTTPS vs HTTP matches exactly
+4. Check for typos in domain name
+
+### Error: "CORS policy: Request header 'content-type' not allowed"
+
+**Cause:** Backend not allowing required headers
+
+**Solutions:**
+1. Verify backend allows `Content-Type` header
+2. Check Flask-CORS configuration in `app.py`
+3. Ensure `allow_headers` includes `Content-Type`
+
+### Error: Mixed Content (HTTP/HTTPS)
+
+**Cause:** Frontend uses HTTPS but backend uses HTTP (or vice versa)
+
+**Solutions:**
+1. Ensure both frontend and backend use HTTPS in production
+2. Update `VITE_FLASK_BACKEND_URL` to use `https://`
+3. Enable HTTPS in CapRover for both apps
+4. Verify Cloudflare SSL/TLS mode is "Full (strict)"
+
+### Error: "CORS policy: Credential is not supported if origin is '*'"
+
+**Cause:** Using `CORS_ALLOWED_ORIGINS=*` with `supports_credentials=True`
+
+**Solutions:**
+1. Set specific origins instead of `*`
+2. Or disable credentials if not needed
+
+## Deployment Scenarios
+
+### Scenario 1: Separate Domains (Recommended for Production)
+
+```
+Frontend: https://frontend.example.com
+Backend:  https://backend.example.com
+```
+
+**Frontend Config:**
+```bash
+VITE_FLASK_BACKEND_URL=https://backend.example.com
+```
+
+**Backend Config:**
+```bash
+CORS_ALLOWED_ORIGINS=https://frontend.example.com
+```
+
+**Pros:** Clean separation, independent scaling
+**Cons:** Requires CORS configuration
+
+### Scenario 2: Single Domain with Proxy
+
+```
+Frontend: https://app.example.com
+Backend:  https://app.example.com/api (proxied)
+```
+
+**Frontend Config:**
+```bash
+VITE_FLASK_BACKEND_URL=/api
+```
+
+**Backend Config:**
+```bash
+CORS_ALLOWED_ORIGINS=*  # Not needed if proxied through nginx
+```
+
+**Nginx Config:** (already configured in `nginx.conf`)
+```nginx
+location /api {
+    proxy_pass http://backend:5000;
+}
+```
+
+**Pros:** No CORS issues (same-origin), simpler configuration
+**Cons:** Tight coupling, single domain
+
+### Scenario 3: Multiple Frontends
+
+```
+Frontend 1: https://app.example.com
+Frontend 2: https://staging.example.com
+Backend:    https://api.example.com
+```
+
+**Frontend Config (both):**
+```bash
+VITE_FLASK_BACKEND_URL=https://api.example.com
+```
+
+**Backend Config:**
+```bash
+CORS_ALLOWED_ORIGINS=https://app.example.com,https://staging.example.com
+```
+
+## Cloudflare-Specific Configuration
+
+### Cloudflare SSL/TLS Mode
+
+Set to **"Full (strict)"** to ensure end-to-end encryption:
+
+1. Cloudflare Dashboard → SSL/TLS → Overview
+2. Select "Full (strict)"
+3. Ensures both Cloudflare-to-origin and client-to-Cloudflare use SSL
+
+### Cloudflare Always Use HTTPS
+
+1. SSL/TLS → Edge Certificates
+2. Enable "Always Use HTTPS"
+3. Automatically redirects HTTP to HTTPS
+
+### Cloudflare Transform Rules (Optional)
+
+Add security headers using Transform Rules:
+
+```
+Header: Strict-Transport-Security
+Value: max-age=31536000; includeSubDomains
+
+Header: X-Content-Type-Options
+Value: nosniff
+
+Header: X-Frame-Options
+Value: DENY
+```
+
+## Automated CORS Testing Script
+
+Save this as `test-cors.sh`:
+
+```bash
+#!/bin/bash
+
+FRONTEND_URL="https://frontend.example.com"
+BACKEND_URL="https://backend.example.com"
+
+echo "Testing CORS Configuration..."
+echo "================================"
+
+echo -e "\n1. Testing Health Endpoint..."
+curl -s "$BACKEND_URL/health" | jq .
+
+echo -e "\n2. Testing OPTIONS Preflight..."
+curl -X OPTIONS "$BACKEND_URL/api/snippets" \
+  -H "Origin: $FRONTEND_URL" \
+  -H "Access-Control-Request-Method: GET" \
+  -i -s | grep -i "access-control"
+
+echo -e "\n3. Testing GET with Origin..."
+curl -s "$BACKEND_URL/api/snippets" \
+  -H "Origin: $FRONTEND_URL" \
+  -i | grep -i "access-control"
+
+echo -e "\n4. Testing POST with Origin..."
+curl -X POST "$BACKEND_URL/api/snippets" \
+  -H "Origin: $FRONTEND_URL" \
+  -H "Content-Type: application/json" \
+  -d '{"id":"test","title":"Test","code":"test","language":"JavaScript","createdAt":"2024-01-01T00:00:00","updatedAt":"2024-01-01T00:00:00"}' \
+  -i -s | grep -i "access-control"
+
+echo -e "\nCORS tests complete!"
+```
+
+Make it executable and run:
+```bash
+chmod +x test-cors.sh
+./test-cors.sh
+```
+
+## Frontend Storage Config Helper
+
+The frontend automatically handles backend configuration through the `getStorageConfig()` function:
+
+### Automatic Configuration
+
+If `VITE_FLASK_BACKEND_URL` is set, the app automatically uses Flask backend:
+
+```typescript
+// src/lib/storage.ts
+function getDefaultConfig(): StorageConfig {
+  const flaskUrl = import.meta.env.VITE_FLASK_BACKEND_URL
+  
+  if (flaskUrl) {
+    return { backend: 'flask', flaskUrl: flaskUrl }
+  }
+  
+  return { backend: 'indexeddb' }
+}
+```
+
+### Manual Configuration
+
+Users can also manually configure in Settings page (if no env var is set).
+
+## Debugging Tips
+
+### Enable Verbose Logging
+
+Add logging to backend `app.py`:
+
+```python
+import logging
+logging.basicConfig(level=logging.DEBUG)
+
+@app.after_request
+def after_request(response):
+    app.logger.debug(f"Response headers: {response.headers}")
+    return response
+```
+
+### Browser DevTools
+
+1. Open DevTools (F12)
+2. Network tab → Enable "Preserve log"
+3. Filter by "Fetch/XHR"
+4. Look for OPTIONS and GET/POST requests
+5. Check Response Headers for `Access-Control-Allow-Origin`
+6. Check Console for CORS error messages
+
+### CapRover Logs
+
+View real-time backend logs:
+
+```bash
+# Via CapRover CLI
+caprover logs codesnippet-backend --lines 100 --follow
+
+# Via Dashboard
+Apps → codesnippet-backend → Logs
+```
+
+## Security Best Practices
+
+### Production CORS Checklist
+
+- [ ] Set specific origins (not `*`)
+- [ ] Use HTTPS for all URLs
+- [ ] Enable Cloudflare proxy (orange cloud)
+- [ ] Set Cloudflare SSL mode to "Full (strict)"
+- [ ] Remove trailing slashes from origin URLs
+- [ ] Test with automated script
+- [ ] Monitor for CORS errors in production logs
+- [ ] Document allowed origins
+
+### Regular Audits
+
+Periodically review:
+1. Which origins are allowed
+2. Whether all origins are still needed
+3. CORS-related errors in logs
+4. Unauthorized access attempts
+
+## Additional Resources
+
+- [MDN CORS Documentation](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS)
+- [Flask-CORS Documentation](https://flask-cors.readthedocs.io/)
+- [Cloudflare SSL/TLS Documentation](https://developers.cloudflare.com/ssl/)
+- [CapRover Environment Variables](https://caprover.com/docs/app-configuration.html)
diff --git a/DEPLOYMENT-CHECKLIST.md b/DEPLOYMENT-CHECKLIST.md
new file mode 100644
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--- /dev/null
+++ b/DEPLOYMENT-CHECKLIST.md
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+# Deployment Checklist
+
+Quick reference checklist for deploying CodeSnippet with separate frontend and backend domains.
+
+## Pre-Deployment
+
+- [ ] CapRover server is running and accessible
+- [ ] Domain name configured in DNS provider (Cloudflare)
+- [ ] CapRover CLI installed: `npm install -g caprover`
+- [ ] Logged into CapRover: `caprover login`
+
+## DNS Configuration (Cloudflare)
+
+- [ ] A record for `frontend.example.com` → CapRover IP (Proxied ☁️)
+- [ ] A record for `backend.example.com` → CapRover IP (Proxied ☁️)
+- [ ] DNS records propagated (check with `dig` or `nslookup`)
+
+## Backend Deployment
+
+- [ ] Create app in CapRover: `codesnippet-backend`
+- [ ] Enable "Has Persistent Data" with path: `/app/data`
+- [ ] Set environment variable: `CORS_ALLOWED_ORIGINS=https://frontend.example.com`
+- [ ] Set environment variable: `DATABASE_PATH=/app/data/snippets.db`
+- [ ] Deploy code: `cd backend && caprover deploy -a codesnippet-backend`
+- [ ] Enable HTTPS in CapRover
+- [ ] Connect custom domain: `backend.example.com`
+- [ ] Force HTTPS redirect enabled
+- [ ] SSL certificate issued successfully
+- [ ] Test health endpoint: `curl https://backend.example.com/health`
+
+## Frontend Deployment
+
+- [ ] Create app in CapRover: `codesnippet-frontend`
+- [ ] Set environment variable: `VITE_FLASK_BACKEND_URL=https://backend.example.com`
+- [ ] Deploy code: `caprover deploy -a codesnippet-frontend` (from project root)
+- [ ] Enable HTTPS in CapRover
+- [ ] Connect custom domain: `frontend.example.com`
+- [ ] Force HTTPS redirect enabled
+- [ ] SSL certificate issued successfully
+- [ ] Test frontend loads: Visit `https://frontend.example.com`
+
+## Cloudflare Configuration
+
+- [ ] SSL/TLS mode set to "Full (strict)"
+- [ ] "Always Use HTTPS" enabled
+- [ ] "Automatic HTTPS Rewrites" enabled
+- [ ] "Auto Minify" enabled (JS, CSS, HTML)
+- [ ] "Brotli" compression enabled
+
+## Testing
+
+- [ ] Backend health check responds: `curl https://backend.example.com/health`
+- [ ] CORS preflight test passes (see CORS-GUIDE.md)
+- [ ] Frontend loads without errors
+- [ ] Backend indicator shows "Backend" status (not "Local")
+- [ ] Can create new snippet
+- [ ] Can view existing snippet
+- [ ] Can edit snippet
+- [ ] Can delete snippet
+- [ ] No CORS errors in browser console (F12)
+- [ ] Mobile responsive layout works
+
+## Post-Deployment
+
+- [ ] Database backup strategy configured
+- [ ] Monitoring enabled (CapRover metrics)
+- [ ] Rate limiting configured (Cloudflare)
+- [ ] Error logging reviewed
+- [ ] Documentation updated with actual URLs
+
+## Security Verification
+
+- [ ] Both domains use HTTPS only
+- [ ] `CORS_ALLOWED_ORIGINS` set to specific domain (not `*`)
+- [ ] Flask debug mode disabled (`debug=False`)
+- [ ] No sensitive data in environment variables
+- [ ] CapRover firewall rules configured
+- [ ] Cloudflare security features enabled
+
+## Quick Commands
+
+### Deploy Backend
+```bash
+cd backend
+caprover deploy -a codesnippet-backend
+```
+
+### Deploy Frontend
+```bash
+caprover deploy -a codesnippet-frontend
+```
+
+### Check Backend Logs
+```bash
+caprover logs codesnippet-backend --lines 100 --follow
+```
+
+### Check Frontend Logs
+```bash
+caprover logs codesnippet-frontend --lines 100 --follow
+```
+
+### Test CORS
+```bash
+curl -X OPTIONS https://backend.example.com/api/snippets \
+  -H "Origin: https://frontend.example.com" \
+  -H "Access-Control-Request-Method: GET" \
+  -v
+```
+
+### Backup Database
+```bash
+docker cp captain--codesnippet-backend:/app/data/snippets.db ./backup-$(date +%Y%m%d).db
+```
+
+## Troubleshooting Quick Fixes
+
+### Frontend can't connect to backend
+1. Check `VITE_FLASK_BACKEND_URL` in frontend environment variables
+2. Verify backend is running: `curl https://backend.example.com/health`
+3. Check CORS configuration in backend
+
+### CORS errors in browser
+1. Verify `CORS_ALLOWED_ORIGINS` includes frontend URL exactly
+2. Ensure both use HTTPS (not mixed HTTP/HTTPS)
+3. Restart backend app after environment changes
+
+### SSL certificate issues
+1. Wait 5-10 minutes for Let's Encrypt
+2. Verify DNS records point to CapRover
+3. Disable and re-enable HTTPS in CapRover
+
+### Data lost after restart
+1. Verify "Has Persistent Data" enabled in backend app
+2. Check persistent directory path: `/app/data`
+3. Verify volume is mounted correctly
+
+## Environment Variables Quick Reference
+
+### Backend (codesnippet-backend)
+```
+CORS_ALLOWED_ORIGINS=https://frontend.example.com
+DATABASE_PATH=/app/data/snippets.db
+```
+
+### Frontend (codesnippet-frontend)
+```
+VITE_FLASK_BACKEND_URL=https://backend.example.com
+```
+
+## Alternative: Single Domain Deployment
+
+For single domain setup (`https://app.example.com`):
+
+### Backend
+- [ ] Deploy backend (internal only, no custom domain)
+- [ ] Set `CORS_ALLOWED_ORIGINS=*` (not needed if proxied)
+
+### Frontend
+- [ ] Set `VITE_FLASK_BACKEND_URL=/api`
+- [ ] nginx proxies `/api` to backend (already configured)
+- [ ] Deploy with custom domain: `app.example.com`
+
+Benefits: No CORS issues, simpler DNS
+Drawbacks: Tightly coupled services
+
+## Rollback Plan
+
+If deployment fails:
+
+1. **Frontend issues:** Redeploy previous version
+2. **Backend issues:** Check logs, fix errors, redeploy
+3. **Database corruption:** Restore from backup
+4. **DNS issues:** Verify Cloudflare settings
+5. **SSL issues:** Disable HTTPS temporarily, debug, re-enable
+
+## Maintenance Schedule
+
+- **Daily:** Check error logs
+- **Weekly:** Review metrics and performance
+- **Monthly:** Update dependencies, security patches
+- **Quarterly:** Review and rotate secrets/keys
+
+## Support Resources
+
+- [Full Deployment Guide](./DEPLOYMENT.md)
+- [CORS Configuration Guide](./CORS-GUIDE.md)
+- [Backend Configuration](./BACKEND-CONFIG.md)
+- [CapRover Documentation](https://caprover.com/docs/)
+- [Cloudflare Documentation](https://developers.cloudflare.com/)
diff --git a/DEPLOYMENT.md b/DEPLOYMENT.md
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--- /dev/null
+++ b/DEPLOYMENT.md
@@ -0,0 +1,380 @@
+# CapRover / Cloudflare Deployment Guide
+
+This guide explains how to deploy CodeSnippet with separate frontend and backend domains using CapRover and Cloudflare.
+
+## Architecture
+
+```
+┌─────────────────────────────────────────────┐
+│          Cloudflare DNS & Proxy             │
+│  https://frontend.example.com               │
+│  https://backend.example.com                │
+└─────────────┬───────────────────────────────┘
+              │
+              │ HTTPS (Cloudflare SSL)
+              │
+┌─────────────▼───────────────────────────────┐
+│             CapRover Server                 │
+│                                             │
+│  ┌──────────────┐      ┌─────────────────┐ │
+│  │   Frontend   │      │    Backend      │ │
+│  │   (Nginx)    │      │    (Flask)      │ │
+│  │   Port 3000  │      │   Port 5000     │ │
+│  └──────────────┘      └─────────────────┘ │
+└─────────────────────────────────────────────┘
+```
+
+## Prerequisites
+
+1. CapRover server installed and configured
+2. Domain name configured in Cloudflare
+3. DNS records pointing to your CapRover server
+4. CapRover CLI installed: `npm install -g caprover`
+
+## Step 1: Configure DNS in Cloudflare
+
+Add these DNS records in Cloudflare:
+
+| Type | Name     | Content              | Proxy Status |
+|------|----------|----------------------|--------------|
+| A    | frontend | YOUR_CAPROVER_IP     | Proxied      |
+| A    | backend  | YOUR_CAPROVER_IP     | Proxied      |
+
+**Important:** Enable "Proxied" (orange cloud) to use Cloudflare's CDN and SSL.
+
+## Step 2: Deploy Backend to CapRover
+
+### Create Backend App
+
+1. Login to CapRover dashboard
+2. Go to "Apps" → "One-Click Apps/Databases"
+3. Create a new app named `codesnippet-backend`
+4. Enable "Has Persistent Data" and set persistent directory to `/app/data`
+
+### Configure Backend Environment Variables
+
+In the backend app settings, add these environment variables:
+
+```bash
+CORS_ALLOWED_ORIGINS=https://frontend.example.com
+DATABASE_PATH=/app/data/snippets.db
+```
+
+### Deploy Backend Code
+
+From the `backend` directory:
+
+```bash
+cd backend
+caprover deploy -a codesnippet-backend
+```
+
+### Enable HTTPS for Backend
+
+1. In CapRover dashboard → Apps → codesnippet-backend
+2. Go to "HTTP Settings"
+3. Enable "HTTPS"
+4. Connect domain: `backend.example.com`
+5. Enable "Force HTTPS by redirecting all HTTP traffic to HTTPS"
+6. Wait for SSL certificate to be issued
+
+## Step 3: Deploy Frontend to CapRover
+
+### Create Frontend App
+
+1. In CapRover dashboard, create new app: `codesnippet-frontend`
+2. No persistent data needed for frontend
+
+### Configure Frontend Environment Variables
+
+In the frontend app settings, add:
+
+```bash
+VITE_FLASK_BACKEND_URL=https://backend.example.com
+```
+
+### Deploy Frontend Code
+
+From the project root:
+
+```bash
+caprover deploy -a codesnippet-frontend
+```
+
+### Enable HTTPS for Frontend
+
+1. In CapRover dashboard → Apps → codesnippet-frontend
+2. Go to "HTTP Settings"
+3. Enable "HTTPS"
+4. Connect domain: `frontend.example.com`
+5. Enable "Force HTTPS by redirecting all HTTP traffic to HTTPS"
+6. Wait for SSL certificate to be issued
+
+## Step 4: Configure Cloudflare Settings
+
+### SSL/TLS Settings
+
+1. Go to Cloudflare dashboard → SSL/TLS
+2. Set encryption mode to "Full (strict)"
+3. Enable "Always Use HTTPS"
+4. Enable "Automatic HTTPS Rewrites"
+
+### Security Settings
+
+1. Go to Security → WAF
+2. Consider enabling Bot Fight Mode for backend
+3. Set up rate limiting rules if needed
+
+### Speed Settings
+
+1. Enable "Auto Minify" for JavaScript, CSS, HTML
+2. Enable "Brotli" compression
+3. Set Browser Cache TTL appropriately
+
+## Step 5: Verify Deployment
+
+### Test Backend
+
+```bash
+curl https://backend.example.com/health
+```
+
+Expected response:
+```json
+{
+  "status": "healthy",
+  "timestamp": "2024-01-01T12:00:00.000000"
+}
+```
+
+### Test CORS
+
+```bash
+curl -H "Origin: https://frontend.example.com" \
+     -H "Access-Control-Request-Method: GET" \
+     -X OPTIONS \
+     https://backend.example.com/api/snippets
+```
+
+Should return CORS headers:
+```
+Access-Control-Allow-Origin: https://frontend.example.com
+Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS
+```
+
+### Test Frontend
+
+Visit `https://frontend.example.com` and verify:
+- Frontend loads correctly
+- Backend indicator shows "Backend" status
+- Can create, edit, and delete snippets
+- No CORS errors in browser console
+
+## Environment Variables Reference
+
+### Backend Environment Variables
+
+| Variable              | Description                                    | Example                          |
+|-----------------------|------------------------------------------------|----------------------------------|
+| `CORS_ALLOWED_ORIGINS`| Comma-separated list of allowed frontend URLs | `https://frontend.example.com`   |
+| `DATABASE_PATH`       | Path to SQLite database file                  | `/app/data/snippets.db`          |
+
+**Note:** Use `*` for `CORS_ALLOWED_ORIGINS` only in development. In production, always specify exact origins.
+
+### Frontend Environment Variables
+
+| Variable                  | Description                  | Example                        |
+|---------------------------|------------------------------|--------------------------------|
+| `VITE_FLASK_BACKEND_URL`  | Backend API URL             | `https://backend.example.com`  |
+
+## Alternative: Single Domain Setup
+
+If you prefer a single domain (e.g., `https://app.example.com`), you can deploy frontend with nginx proxying to backend:
+
+### Deploy Both Services
+
+1. Deploy backend as before (internal only, no custom domain)
+2. Frontend proxies `/api` requests to backend via nginx
+
+### Frontend Configuration
+
+```bash
+# Frontend environment variables
+VITE_FLASK_BACKEND_URL=/api
+```
+
+### Nginx Configuration
+
+The included `nginx.conf` already handles this:
+
+```nginx
+location /api {
+    proxy_pass http://backend:5000;
+    # ... proxy headers
+}
+```
+
+### Benefits
+
+- Simplified DNS (single domain)
+- No CORS issues (same-origin requests)
+- Easier SSL management
+
+### Drawbacks
+
+- Frontend and backend tightly coupled
+- Can't independently scale services
+- Single point of failure
+
+## Troubleshooting
+
+### CORS Errors
+
+**Problem:** Browser console shows CORS errors
+
+**Solutions:**
+1. Verify `CORS_ALLOWED_ORIGINS` in backend matches frontend URL exactly
+2. Ensure both domains use HTTPS (not mixed HTTP/HTTPS)
+3. Check Cloudflare proxy status is enabled for both domains
+4. Clear browser cache and hard refresh
+
+### Backend Connection Failed
+
+**Problem:** Frontend shows "Connection failed" error
+
+**Solutions:**
+1. Verify backend is running: `curl https://backend.example.com/health`
+2. Check CapRover logs for backend app
+3. Verify `VITE_FLASK_BACKEND_URL` in frontend matches backend URL
+4. Test from command line: `curl -v https://backend.example.com/api/snippets`
+
+### SSL Certificate Issues
+
+**Problem:** SSL certificate not issued or invalid
+
+**Solutions:**
+1. Wait 5-10 minutes for Let's Encrypt to issue certificate
+2. Verify DNS records are correct and propagated
+3. Check CapRover can reach Let's Encrypt (port 80 open)
+4. Try disabling and re-enabling HTTPS in CapRover
+
+### Data Persistence Issues
+
+**Problem:** Backend loses data after restart
+
+**Solutions:**
+1. Verify "Has Persistent Data" is enabled in CapRover
+2. Check persistent directory path is `/app/data`
+3. Verify `DATABASE_PATH` environment variable is correct
+4. Check CapRover volume is properly mounted
+
+### Multiple Origins
+
+**Problem:** Need to allow multiple frontend domains
+
+**Solution:** Set comma-separated origins:
+```bash
+CORS_ALLOWED_ORIGINS=https://frontend.example.com,https://app.example.com,https://staging.example.com
+```
+
+## Security Best Practices
+
+### Production Checklist
+
+- [ ] HTTPS enabled for both frontend and backend
+- [ ] `CORS_ALLOWED_ORIGINS` set to specific domains (not `*`)
+- [ ] Cloudflare proxy enabled (orange cloud)
+- [ ] Rate limiting configured in Cloudflare
+- [ ] Backend database backed up regularly
+- [ ] Environment variables stored securely (not in code)
+- [ ] Debug mode disabled in Flask (`debug=False`)
+- [ ] Cloudflare WAF rules configured
+- [ ] HTTPS-only cookies enabled
+- [ ] Security headers configured in nginx
+
+### Recommended Cloudflare Rules
+
+1. **Rate Limiting:** Limit API requests to 100 per minute per IP
+2. **Bot Protection:** Challenge or block known bad bots
+3. **Geographic Restrictions:** Block countries you don't serve (optional)
+4. **DDoS Protection:** Enable automatic DDoS mitigation
+
+## Monitoring
+
+### CapRover Monitoring
+
+1. Enable app metrics in CapRover dashboard
+2. Monitor CPU and memory usage
+3. Set up alerts for app crashes
+4. Review logs regularly for errors
+
+### Cloudflare Analytics
+
+1. Monitor traffic patterns
+2. Check for unusual spikes or attacks
+3. Review security events
+4. Analyze performance metrics
+
+## Backup Strategy
+
+### Automated Backups
+
+Set up a cron job in CapRover to backup database:
+
+```bash
+# In backend app settings, add a schedule:
+0 2 * * * tar -czf /app/data/backup-$(date +%Y%m%d).tar.gz /app/data/snippets.db
+```
+
+### Manual Backup
+
+1. SSH into CapRover server
+2. Copy database file:
+   ```bash
+   docker cp captain--codesnippet-backend:/app/data/snippets.db ./backup.db
+   ```
+
+### Restore from Backup
+
+1. Copy backup to container:
+   ```bash
+   docker cp ./backup.db captain--codesnippet-backend:/app/data/snippets.db
+   ```
+2. Restart backend app in CapRover
+
+## Scaling Considerations
+
+### Vertical Scaling
+
+Increase resources in CapRover:
+1. Go to app settings → "Resources"
+2. Increase CPU and memory limits
+3. Restart app
+
+### Horizontal Scaling
+
+For high traffic:
+1. Deploy multiple backend instances in CapRover
+2. Use CapRover's load balancing
+3. Consider shared database (PostgreSQL instead of SQLite)
+4. Use Redis for session management
+
+## Cost Optimization
+
+### Cloudflare
+
+- Free plan includes SSL, CDN, and basic DDoS protection
+- Pro plan ($20/mo) adds WAF and additional performance features
+
+### CapRover
+
+- Single VPS can run both frontend and backend
+- Recommended: 2 CPU / 4GB RAM minimum
+- Estimated cost: $10-20/month (DigitalOcean, Linode, Vultr)
+
+## Support
+
+For issues specific to:
+- **CapRover:** https://caprover.com/docs/
+- **Cloudflare:** https://support.cloudflare.com/
+- **CodeSnippet:** Check the main README.md and BACKEND-CONFIG.md
diff --git a/ENV-CONFIG.md b/ENV-CONFIG.md
new file mode 100644
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--- /dev/null
+++ b/ENV-CONFIG.md
@@ -0,0 +1,329 @@
+# Environment Configuration Examples
+
+This directory contains example environment configurations for different deployment scenarios.
+
+## Quick Reference
+
+Copy the appropriate example to `.env` in the project root:
+
+```bash
+cp .env.example .env
+# Edit .env with your values
+```
+
+## Scenarios
+
+### 1. Local Development (Default)
+
+**Use case:** Developing frontend only with local browser storage
+
+```bash
+# No backend URL - uses IndexedDB
+VITE_FLASK_BACKEND_URL=
+```
+
+### 2. Local Development with Backend
+
+**Use case:** Developing with local Flask backend
+
+```bash
+# Frontend (.env)
+VITE_FLASK_BACKEND_URL=http://localhost:5000
+
+# Backend (environment or .env)
+CORS_ALLOWED_ORIGINS=http://localhost:3000,http://localhost:5173
+DATABASE_PATH=/app/data/snippets.db
+```
+
+### 3. Docker Compose (Full Stack)
+
+**Use case:** Running both frontend and backend with Docker
+
+```bash
+# Frontend automatically connects to backend via nginx proxy
+# No .env needed - configured in docker-compose.yml
+```
+
+**docker-compose.yml already includes:**
+```yaml
+environment:
+  - VITE_FLASK_BACKEND_URL=http://localhost:5000
+  - CORS_ALLOWED_ORIGINS=http://localhost:3000
+  - DATABASE_PATH=/app/data/snippets.db
+```
+
+### 4. Production - Separate Domains (CapRover)
+
+**Use case:** Frontend and backend on different domains
+
+```bash
+# Frontend environment variables (in CapRover)
+VITE_FLASK_BACKEND_URL=https://backend.example.com
+
+# Backend environment variables (in CapRover)
+CORS_ALLOWED_ORIGINS=https://frontend.example.com
+DATABASE_PATH=/app/data/snippets.db
+```
+
+### 5. Production - Multiple Frontend Domains
+
+**Use case:** Multiple frontend deployments (prod, staging, dev)
+
+```bash
+# Backend environment variables
+CORS_ALLOWED_ORIGINS=https://app.example.com,https://staging.example.com,https://dev.example.com
+DATABASE_PATH=/app/data/snippets.db
+
+# Frontend 1 (Production)
+VITE_FLASK_BACKEND_URL=https://api.example.com
+
+# Frontend 2 (Staging)
+VITE_FLASK_BACKEND_URL=https://api.example.com
+
+# Frontend 3 (Development)
+VITE_FLASK_BACKEND_URL=https://api.example.com
+```
+
+### 6. Production - Single Domain (Proxied)
+
+**Use case:** Frontend and backend on same domain, nginx proxy
+
+```bash
+# Frontend environment variables
+VITE_FLASK_BACKEND_URL=/api
+
+# Backend environment variables
+CORS_ALLOWED_ORIGINS=*
+# Note: CORS not needed since nginx proxies requests (same-origin)
+DATABASE_PATH=/app/data/snippets.db
+```
+
+**nginx.conf includes:**
+```nginx
+location /api {
+    proxy_pass http://backend:5000;
+}
+```
+
+## Environment Variables Reference
+
+### Frontend Variables
+
+| Variable | Description | Example |
+|----------|-------------|---------|
+| `VITE_FLASK_BACKEND_URL` | Backend API URL. When set, forces Flask backend usage. | `https://backend.example.com` |
+
+**Notes:**
+- Must start with `VITE_` to be exposed to frontend
+- If not set, app uses IndexedDB (local storage)
+- Can be relative (`/api`) if using nginx proxy
+- Requires rebuild for production: `npm run build`
+
+### Backend Variables
+
+| Variable | Description | Example |
+|----------|-------------|---------|
+| `CORS_ALLOWED_ORIGINS` | Comma-separated list of allowed origins | `https://frontend.example.com` |
+| `DATABASE_PATH` | Path to SQLite database file | `/app/data/snippets.db` |
+
+**Notes:**
+- Use `*` only in development
+- In production, always specify exact origins
+- No trailing slashes on URLs
+- Must match frontend URL exactly (including https://)
+
+## Setting Environment Variables
+
+### Local Development (.env file)
+
+```bash
+# Create .env file
+cat > .env << EOF
+VITE_FLASK_BACKEND_URL=http://localhost:5000
+EOF
+
+# Start dev server
+npm run dev
+```
+
+### Docker Build
+
+```bash
+# Build with environment variable
+docker build --build-arg VITE_FLASK_BACKEND_URL=https://backend.example.com -t frontend .
+```
+
+### Docker Compose
+
+```yaml
+# docker-compose.yml
+services:
+  frontend:
+    environment:
+      - VITE_FLASK_BACKEND_URL=https://backend.example.com
+```
+
+### CapRover
+
+1. Go to CapRover dashboard
+2. Select your app
+3. Click "App Configs" tab
+4. Add environment variables in "Environment Variables" section
+5. Redeploy app
+
+### Kubernetes
+
+```yaml
+# deployment.yaml
+env:
+  - name: VITE_FLASK_BACKEND_URL
+    value: "https://backend.example.com"
+  - name: CORS_ALLOWED_ORIGINS
+    value: "https://frontend.example.com"
+```
+
+## Testing Configuration
+
+### Test Frontend Backend Connection
+
+```bash
+# Check if environment variable is set
+echo $VITE_FLASK_BACKEND_URL
+
+# Check in browser console
+console.log(import.meta.env.VITE_FLASK_BACKEND_URL)
+```
+
+### Test Backend CORS
+
+```bash
+# Quick test
+curl -H "Origin: https://frontend.example.com" \
+     -H "Access-Control-Request-Method: GET" \
+     -X OPTIONS \
+     https://backend.example.com/api/snippets
+
+# Full test suite
+./test-cors.sh https://backend.example.com https://frontend.example.com
+```
+
+## Common Mistakes
+
+### ❌ Wrong: Missing VITE_ Prefix
+
+```bash
+FLASK_BACKEND_URL=http://localhost:5000  # Won't work!
+```
+
+### ✅ Correct: VITE_ Prefix Required
+
+```bash
+VITE_FLASK_BACKEND_URL=http://localhost:5000
+```
+
+---
+
+### ❌ Wrong: Trailing Slash in CORS
+
+```bash
+CORS_ALLOWED_ORIGINS=https://frontend.example.com/  # Won't work!
+```
+
+### ✅ Correct: No Trailing Slash
+
+```bash
+CORS_ALLOWED_ORIGINS=https://frontend.example.com
+```
+
+---
+
+### ❌ Wrong: HTTP/HTTPS Mismatch
+
+```bash
+# Frontend
+VITE_FLASK_BACKEND_URL=https://backend.example.com
+
+# Backend
+CORS_ALLOWED_ORIGINS=http://frontend.example.com  # Wrong protocol!
+```
+
+### ✅ Correct: Matching Protocols
+
+```bash
+# Frontend
+VITE_FLASK_BACKEND_URL=https://backend.example.com
+
+# Backend
+CORS_ALLOWED_ORIGINS=https://frontend.example.com
+```
+
+---
+
+### ❌ Wrong: Using * in Production
+
+```bash
+CORS_ALLOWED_ORIGINS=*  # Security risk in production!
+```
+
+### ✅ Correct: Specific Origins
+
+```bash
+CORS_ALLOWED_ORIGINS=https://frontend.example.com
+```
+
+## Troubleshooting
+
+### Environment variable not working
+
+1. **Frontend not rebuilding:**
+   - Vite requires rebuild for env vars: `npm run build`
+   - Dev server: Restart `npm run dev`
+
+2. **Variable not prefixed correctly:**
+   - Must start with `VITE_` for frontend
+   - Backend vars don't need prefix
+
+3. **Docker not picking up changes:**
+   - Rebuild: `docker-compose up -d --build`
+   - Check: `docker-compose config`
+
+### CORS errors persist
+
+1. **Backend not restarted:**
+   - Restart after env changes
+   - Check logs: `docker-compose logs backend`
+
+2. **URL mismatch:**
+   - Frontend URL must match CORS_ALLOWED_ORIGINS exactly
+   - Check browser console for actual origin
+
+3. **Cloudflare issues:**
+   - Verify proxy status (orange cloud)
+   - Check SSL/TLS mode: "Full (strict)"
+
+## Security Best Practices
+
+### Development
+- ✅ Use `*` for CORS_ALLOWED_ORIGINS
+- ✅ Use http:// for local URLs
+- ✅ Keep .env out of version control
+
+### Staging
+- ✅ Use specific origins for CORS
+- ✅ Use https:// for all URLs
+- ✅ Test with production-like configuration
+
+### Production
+- ✅ Always use specific origins
+- ✅ Always use https://
+- ✅ Store secrets in secure environment
+- ✅ Never commit .env files
+- ✅ Rotate credentials regularly
+- ✅ Monitor access logs
+
+## Additional Resources
+
+- [Backend Configuration Guide](./BACKEND-CONFIG.md)
+- [CORS Configuration & Testing](./CORS-GUIDE.md)
+- [Deployment Guide](./DEPLOYMENT.md)
+- [Deployment Checklist](./DEPLOYMENT-CHECKLIST.md)
diff --git a/README.md b/README.md
index 2a04e31..1ea3d21 100644
--- a/README.md
+++ b/README.md
@@ -74,10 +74,18 @@ When set, the app automatically connects to Flask backend and disables manual co
 
 ## 📚 Documentation
 
+### Getting Started
 - **[Quick Start Guide](./QUICKSTART.md)** - Get up and running quickly
 - **[Application Guide](./README-APP.md)** - Features and usage
-- **[Backend Configuration](./BACKEND-CONFIG.md)** - Detailed backend setup
+
+### Backend & Storage
+- **[Backend Configuration](./BACKEND-CONFIG.md)** - Detailed backend setup and environment variables
 - **[Backend API](./backend/README.md)** - Flask API documentation
+
+### Production Deployment
+- **[Deployment Guide](./DEPLOYMENT.md)** - Complete CapRover/Cloudflare deployment walkthrough
+- **[CORS Configuration](./CORS-GUIDE.md)** - CORS setup and troubleshooting
+- **[Deployment Checklist](./DEPLOYMENT-CHECKLIST.md)** - Quick deployment reference
 - **[Docker Examples](./docker-compose.README.md)** - Docker deployment options
 
 ## 🛠️ Technology Stack
diff --git a/backend/Dockerfile b/backend/Dockerfile
index 1789c9c..35e1b8e 100644
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@@ -7,10 +7,12 @@ RUN pip install --no-cache-dir -r requirements.txt
 
 COPY app.py .
 
-RUN mkdir -p /data
+RUN mkdir -p /app/data
+
+ENV FLASK_APP=app.py
+ENV DATABASE_PATH=/app/data/snippets.db
+ENV CORS_ALLOWED_ORIGINS=*
 
 EXPOSE 5000
 
-ENV DB_PATH=/data/snippets.db
-
 CMD ["python", "app.py"]
diff --git a/backend/README.md b/backend/README.md
index 423869c..abce013 100644
--- a/backend/README.md
+++ b/backend/README.md
@@ -113,10 +113,14 @@ docker build -t codesnippet-backend ./backend
 
 ```bash
 # With volume for persistent data
-docker run -p 5000:5000 -v $(pwd)/data:/data codesnippet-backend
+docker run -p 5000:5000 -v $(pwd)/data:/app/data codesnippet-backend
 
-# With custom database path
-docker run -p 5000:5000 -e DB_PATH=/data/custom.db -v $(pwd)/data:/data codesnippet-backend
+# With custom database path and CORS
+docker run -p 5000:5000 \
+  -e DATABASE_PATH=/app/data/custom.db \
+  -e CORS_ALLOWED_ORIGINS=https://frontend.example.com \
+  -v $(pwd)/data:/app/data \
+  codesnippet-backend
 ```
 
 ### Using Docker Compose
@@ -162,7 +166,24 @@ CREATE TABLE snippets (
 
 ## Environment Variables
 
-- `DB_PATH` - Path to SQLite database file (default: `/data/snippets.db`)
+| Variable | Description | Default | Example |
+|----------|-------------|---------|---------|
+| `DATABASE_PATH` | Path to SQLite database file | `/app/data/snippets.db` | `/app/data/snippets.db` |
+| `CORS_ALLOWED_ORIGINS` | Comma-separated list of allowed frontend origins | `*` (all origins) | `https://frontend.example.com` |
+
+### Production Configuration
+
+For production deployments, always set specific CORS origins:
+
+```bash
+# Single origin
+export CORS_ALLOWED_ORIGINS=https://frontend.example.com
+
+# Multiple origins
+export CORS_ALLOWED_ORIGINS=https://frontend.example.com,https://app.example.com
+```
+
+**Important:** Using `*` for CORS in production is a security risk. Only use in development.
 
 ## Troubleshooting
 
@@ -172,9 +193,34 @@ CREATE TABLE snippets (
 - Verify the port (5000) is not in use
 
 ### CORS Errors
-- The backend allows all origins by default
-- Modify `CORS(app)` in `app.py` if you need to restrict origins
+- The backend allows all origins by default in development (`CORS_ALLOWED_ORIGINS=*`)
+- For production, set specific origins: `CORS_ALLOWED_ORIGINS=https://frontend.example.com`
+- See [CORS-GUIDE.md](../CORS-GUIDE.md) for detailed CORS configuration and testing
+- Verify frontend URL matches exactly (including https:// and no trailing slash)
 
 ### Database Locked
 - Ensure only one instance of the backend is running
 - Check file permissions on the database file
+
+## Production Deployment
+
+For deploying to production with separate frontend and backend domains:
+
+1. **See [DEPLOYMENT.md](../DEPLOYMENT.md)** - Complete CapRover/Cloudflare deployment guide
+2. **See [CORS-GUIDE.md](../CORS-GUIDE.md)** - CORS configuration and testing
+3. **See [DEPLOYMENT-CHECKLIST.md](../DEPLOYMENT-CHECKLIST.md)** - Quick deployment checklist
+
+### Quick Production Setup
+
+```bash
+# Build and deploy backend to CapRover
+cd backend
+caprover deploy -a codesnippet-backend
+
+# Set environment variables in CapRover dashboard:
+# - CORS_ALLOWED_ORIGINS=https://frontend.example.com
+# - DATABASE_PATH=/app/data/snippets.db
+
+# Enable persistent storage at /app/data
+# Enable HTTPS and connect custom domain
+```
diff --git a/backend/app.py b/backend/app.py
index 8fcfbbd..afa9f98 100644
--- a/backend/app.py
+++ b/backend/app.py
@@ -1,181 +1,191 @@
-from flask import Flask, request, jsonify
-from flask_cors import CORS
-from datetime 
-
-from datetime import datetime
-import os
-
-app = Flask(__name__)
-
-
-    cursor = conn.cursor()
-
-            i
-            code TEXT NOT NULL,
-            description TEXT,
-            cat
-
-            up
-    ''')
-    conn.commit()
-
-def 
-
-def get_snippets():
-        conn = get_db()
-        cursor.execute('SELECT *
-        conn.close()
-        snippets = []
-            snippet = dict(ro
-                snippe
-                snippet['p
-        
-    except Exception as e:
-
-            updatedAt TEXT NOT NULL
-        )
-    ''')
-    
-    conn.commit()
-    conn.close()
-
-@app.route('/health', methods=['GET'])
-def health():
-    return jsonify({'status': 'healthy', 'timestamp': datetime.utcnow().isoformat()})
-
-@app.route('/api/snippets', methods=['GET'])
-def get_snippets():
-        
-        conn = get_db()
-        preview_params_json = 
-        cursor.execute('SELECT * FROM snippets ORDER BY updatedAt DESC')
-        rows = cursor.fetchall()
-        conn.close()
-        
-        snippets = []
-        for row in rows:
-            snippet = dict(row)
-            if snippet.get('tags'):
-                snippet['tags'] = json.loads(snippet['tags'])
-            if snippet.get('previewParams'):
-                snippet['previewParams'] = json.loads(snippet['previewParams'])
-            snippets.append(snippet)
-        
-        return jsonify(snippets)
-    except Exception as e:
-        return jsonify({'error': str(e)}), 500
-
-@app.route('/api/snippets/<snippet_id>', methods=['GET'])
-            UPDATE snippets
-        
-            data['title
-            data['language'],
-            tags_json,
-            data.get('component
-            data['up
-        
-        conn.commit
-        
-        
-        return jsonify(data
-        return jsonify({'error'
-@app.route('/api/snippets/<snippet_id>', methods=['DELETE
-    try:
-        cursor = conn.cursor()
-        
-        
-            return jsonify
-        return jsonify({'success': True})
-
-if __name__ == '__main__':
-    app.run(host='0.0
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-            UPDATE snippets
-            SET title = ?, code = ?, language = ?, description = ?, tags = ?, category = ?, componentName = ?, previewParams = ?, updatedAt = ?
-            WHERE id = ?
-        ''', (
-            data['title'],
-            data['code'],
-            data['language'],
-            data.get('description', ''),
-            tags_json,
-            data.get('category', 'general'),
-            data.get('componentName', ''),
-            preview_params_json,
-            data['updatedAt'],
-            snippet_id
-        ))
-        
-        conn.commit()
-        conn.close()
-        
-        if cursor.rowcount == 0:
-            return jsonify({'error': 'Snippet not found'}), 404
-        
-        return jsonify(data)
-    except Exception as e:
-        return jsonify({'error': str(e)}), 500
-
-@app.route('/api/snippets/<snippet_id>', methods=['DELETE'])
-def delete_snippet(snippet_id):
-    try:
-        conn = get_db()
-        cursor = conn.cursor()
-        cursor.execute('DELETE FROM snippets WHERE id = ?', (snippet_id,))
-        conn.commit()
-        conn.close()
-        
-        if cursor.rowcount == 0:
-            return jsonify({'error': 'Snippet not found'}), 404
-        
-        return jsonify({'success': True})
-    except Exception as e:
-        return jsonify({'error': str(e)}), 500
-
-if __name__ == '__main__':
-    init_db()
-    app.run(host='0.0.0.0', port=5000, debug=True)
+from flask import Flask, request, jsonify
+from flask_cors import CORS
+from datetime import datetime
+import sqlite3
+import json
+import os
+
+app = Flask(__name__)
+
+ALLOWED_ORIGINS = os.environ.get('CORS_ALLOWED_ORIGINS', '*')
+if ALLOWED_ORIGINS == '*':
+    CORS(app, 
+         origins='*',
+         methods=['GET', 'POST', 'PUT', 'DELETE', 'OPTIONS'],
+         allow_headers=['Content-Type', 'Authorization'],
+         supports_credentials=False)
+else:
+    origins_list = [origin.strip() for origin in ALLOWED_ORIGINS.split(',')]
+    CORS(app, 
+         origins=origins_list,
+         methods=['GET', 'POST', 'PUT', 'DELETE', 'OPTIONS'],
+         allow_headers=['Content-Type', 'Authorization'],
+         supports_credentials=True)
+
+DATABASE_PATH = os.environ.get('DATABASE_PATH', '/app/data/snippets.db')
+os.makedirs(os.path.dirname(DATABASE_PATH), exist_ok=True)
+
+def get_db():
+    conn = sqlite3.connect(DATABASE_PATH)
+    conn.row_factory = sqlite3.Row
+    return conn
+
+def init_db():
+    conn = get_db()
+    cursor = conn.cursor()
+    cursor.execute('''
+        CREATE TABLE IF NOT EXISTS snippets (
+            id TEXT PRIMARY KEY,
+            title TEXT NOT NULL,
+            code TEXT NOT NULL,
+            language TEXT NOT NULL,
+            description TEXT,
+            tags TEXT,
+            category TEXT DEFAULT 'general',
+            componentName TEXT,
+            previewParams TEXT,
+            createdAt TEXT NOT NULL,
+            updatedAt TEXT NOT NULL
+        )
+    ''')
+    conn.commit()
+    conn.close()
+
+@app.route('/health', methods=['GET'])
+def health():
+    return jsonify({'status': 'healthy', 'timestamp': datetime.utcnow().isoformat()})
+
+@app.route('/api/snippets', methods=['GET'])
+def get_snippets():
+    try:
+        conn = get_db()
+        cursor = conn.cursor()
+        cursor.execute('SELECT * FROM snippets ORDER BY updatedAt DESC')
+        rows = cursor.fetchall()
+        conn.close()
+        
+        snippets = []
+        for row in rows:
+            snippet = dict(row)
+            if snippet.get('tags'):
+                snippet['tags'] = json.loads(snippet['tags'])
+            if snippet.get('previewParams'):
+                snippet['previewParams'] = json.loads(snippet['previewParams'])
+            snippets.append(snippet)
+        
+        return jsonify(snippets)
+    except Exception as e:
+        return jsonify({'error': str(e)}), 500
+
+@app.route('/api/snippets/<snippet_id>', methods=['GET'])
+def get_snippet(snippet_id):
+    try:
+        conn = get_db()
+        cursor = conn.cursor()
+        cursor.execute('SELECT * FROM snippets WHERE id = ?', (snippet_id,))
+        row = cursor.fetchone()
+        conn.close()
+        
+        if not row:
+            return jsonify({'error': 'Snippet not found'}), 404
+        
+        snippet = dict(row)
+        if snippet.get('tags'):
+            snippet['tags'] = json.loads(snippet['tags'])
+        if snippet.get('previewParams'):
+            snippet['previewParams'] = json.loads(snippet['previewParams'])
+        
+        return jsonify(snippet)
+    except Exception as e:
+        return jsonify({'error': str(e)}), 500
+
+@app.route('/api/snippets', methods=['POST'])
+def create_snippet():
+    try:
+        data = request.json
+        conn = get_db()
+        cursor = conn.cursor()
+        
+        tags_json = json.dumps(data.get('tags', []))
+        preview_params_json = json.dumps(data.get('previewParams', {}))
+        
+        cursor.execute('''
+            INSERT INTO snippets (id, title, code, language, description, tags, category, componentName, previewParams, createdAt, updatedAt)
+            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+        ''', (
+            data['id'],
+            data['title'],
+            data['code'],
+            data['language'],
+            data.get('description', ''),
+            tags_json,
+            data.get('category', 'general'),
+            data.get('componentName', ''),
+            preview_params_json,
+            data['createdAt'],
+            data['updatedAt']
+        ))
+        
+        conn.commit()
+        conn.close()
+        
+        return jsonify(data), 201
+    except Exception as e:
+        return jsonify({'error': str(e)}), 500
+
+@app.route('/api/snippets/<snippet_id>', methods=['PUT'])
+def update_snippet(snippet_id):
+    try:
+        data = request.json
+        conn = get_db()
+        cursor = conn.cursor()
+        
+        tags_json = json.dumps(data.get('tags', []))
+        preview_params_json = json.dumps(data.get('previewParams', {}))
+        
+        cursor.execute('''
+            UPDATE snippets
+            SET title = ?, code = ?, language = ?, description = ?, tags = ?, category = ?, componentName = ?, previewParams = ?, updatedAt = ?
+            WHERE id = ?
+        ''', (
+            data['title'],
+            data['code'],
+            data['language'],
+            data.get('description', ''),
+            tags_json,
+            data.get('category', 'general'),
+            data.get('componentName', ''),
+            preview_params_json,
+            data['updatedAt'],
+            snippet_id
+        ))
+        
+        conn.commit()
+        conn.close()
+        
+        if cursor.rowcount == 0:
+            return jsonify({'error': 'Snippet not found'}), 404
+        
+        return jsonify(data)
+    except Exception as e:
+        return jsonify({'error': str(e)}), 500
+
+@app.route('/api/snippets/<snippet_id>', methods=['DELETE'])
+def delete_snippet(snippet_id):
+    try:
+        conn = get_db()
+        cursor = conn.cursor()
+        cursor.execute('DELETE FROM snippets WHERE id = ?', (snippet_id,))
+        conn.commit()
+        conn.close()
+        
+        if cursor.rowcount == 0:
+            return jsonify({'error': 'Snippet not found'}), 404
+        
+        return jsonify({'success': True})
+    except Exception as e:
+        return jsonify({'error': str(e)}), 500
+
+if __name__ == '__main__':
+    init_db()
+    app.run(host='0.0.0.0', port=5000, debug=False)
diff --git a/backend/captain-definition b/backend/captain-definition
new file mode 100644
index 0000000..0e14f82
--- /dev/null
+++ b/backend/captain-definition
@@ -0,0 +1,4 @@
+{
+  "schemaVersion": 2,
+  "dockerfilePath": "./Dockerfile"
+}
diff --git a/captain-definition b/captain-definition
new file mode 100644
index 0000000..0e14f82
--- /dev/null
+++ b/captain-definition
@@ -0,0 +1,4 @@
+{
+  "schemaVersion": 2,
+  "dockerfilePath": "./Dockerfile"
+}
diff --git a/docker-compose.production.yml b/docker-compose.production.yml
new file mode 100644
index 0000000..234c7bb
--- /dev/null
+++ b/docker-compose.production.yml
@@ -0,0 +1,35 @@
+version: '3.8'
+
+services:
+  backend:
+    build: ./backend
+    ports:
+      - "5000:5000"
+    volumes:
+      - snippet-data:/app/data
+    environment:
+      - DATABASE_PATH=/app/data/snippets.db
+      - CORS_ALLOWED_ORIGINS=https://frontend.example.com,https://app.example.com
+    restart: unless-stopped
+    networks:
+      - app-network
+
+  frontend:
+    build:
+      context: .
+      args:
+        - VITE_FLASK_BACKEND_URL=https://backend.example.com
+    ports:
+      - "3000:3000"
+    depends_on:
+      - backend
+    restart: unless-stopped
+    networks:
+      - app-network
+
+volumes:
+  snippet-data:
+
+networks:
+  app-network:
+    driver: bridge
diff --git a/docker-compose.yml b/docker-compose.yml
index 76172c1..f70dd80 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -6,9 +6,10 @@ services:
     ports:
       - "5000:5000"
     volumes:
-      - snippet-data:/data
+      - snippet-data:/app/data
     environment:
-      - DB_PATH=/data/snippets.db
+      - DATABASE_PATH=/app/data/snippets.db
+      - CORS_ALLOWED_ORIGINS=http://localhost:3000
     restart: unless-stopped
 
   frontend:
@@ -18,8 +19,6 @@ services:
         - VITE_FLASK_BACKEND_URL=http://localhost:5000
     ports:
       - "3000:3000"
-    environment:
-      - VITE_FLASK_BACKEND_URL=http://backend:5000
     depends_on:
       - backend
     restart: unless-stopped
diff --git a/nginx.conf b/nginx.conf
index 10f81be..ae726e1 100644
--- a/nginx.conf
+++ b/nginx.conf
@@ -6,6 +6,10 @@ server {
 
     location / {
         try_files $uri $uri/ /index.html;
+        
+        add_header Cache-Control "no-cache, no-store, must-revalidate";
+        add_header Pragma "no-cache";
+        add_header Expires "0";
     }
 
     location /api {
@@ -14,6 +18,12 @@ server {
         proxy_set_header Upgrade $http_upgrade;
         proxy_set_header Connection 'upgrade';
         proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
         proxy_cache_bypass $http_upgrade;
+        
+        proxy_buffering off;
+        proxy_request_buffering off;
     }
 }
diff --git a/test-cors.sh b/test-cors.sh
new file mode 100644
index 0000000..35dc410
--- /dev/null
+++ b/test-cors.sh
@@ -0,0 +1,138 @@
+#!/bin/bash
+
+# CORS Testing Script for CodeSnippet
+# Usage: ./test-cors.sh [BACKEND_URL] [FRONTEND_URL]
+# Example: ./test-cors.sh https://backend.example.com https://frontend.example.com
+
+BACKEND_URL="${1:-http://localhost:5000}"
+FRONTEND_URL="${2:-http://localhost:3000}"
+
+echo "======================================"
+echo "CodeSnippet CORS Testing Script"
+echo "======================================"
+echo "Backend URL:  $BACKEND_URL"
+echo "Frontend URL: $FRONTEND_URL"
+echo "======================================"
+echo ""
+
+# Test 1: Health Check
+echo "🔍 Test 1: Health Check (No CORS required)"
+echo "--------------------------------------"
+HEALTH_RESPONSE=$(curl -s "$BACKEND_URL/health")
+if [ $? -eq 0 ]; then
+    echo "✅ Health check successful"
+    echo "Response: $HEALTH_RESPONSE"
+else
+    echo "❌ Health check failed - backend may not be running"
+    exit 1
+fi
+echo ""
+
+# Test 2: OPTIONS Preflight
+echo "🔍 Test 2: OPTIONS Preflight Request"
+echo "--------------------------------------"
+PREFLIGHT_HEADERS=$(curl -s -X OPTIONS "$BACKEND_URL/api/snippets" \
+    -H "Origin: $FRONTEND_URL" \
+    -H "Access-Control-Request-Method: GET" \
+    -H "Access-Control-Request-Headers: Content-Type" \
+    -i | grep -i "access-control")
+
+if echo "$PREFLIGHT_HEADERS" | grep -q "access-control-allow-origin"; then
+    echo "✅ CORS preflight successful"
+    echo "$PREFLIGHT_HEADERS"
+else
+    echo "❌ CORS preflight failed - missing CORS headers"
+    echo "Response headers:"
+    curl -s -X OPTIONS "$BACKEND_URL/api/snippets" \
+        -H "Origin: $FRONTEND_URL" \
+        -H "Access-Control-Request-Method: GET" \
+        -i | head -n 20
+fi
+echo ""
+
+# Test 3: GET with Origin
+echo "🔍 Test 3: GET Request with Origin"
+echo "--------------------------------------"
+GET_HEADERS=$(curl -s "$BACKEND_URL/api/snippets" \
+    -H "Origin: $FRONTEND_URL" \
+    -i | grep -i "access-control")
+
+if echo "$GET_HEADERS" | grep -q "access-control-allow-origin"; then
+    echo "✅ GET request CORS successful"
+    echo "$GET_HEADERS"
+else
+    echo "❌ GET request CORS failed - missing CORS headers"
+fi
+echo ""
+
+# Test 4: POST with Origin
+echo "🔍 Test 4: POST Request with Origin"
+echo "--------------------------------------"
+TEST_SNIPPET='{
+  "id": "test-cors-'$(date +%s)'",
+  "title": "CORS Test Snippet",
+  "code": "console.log(\"CORS test\");",
+  "language": "JavaScript",
+  "description": "Test snippet for CORS validation",
+  "tags": ["test"],
+  "category": "general",
+  "createdAt": "'$(date -u +"%Y-%m-%dT%H:%M:%S.000Z")'",
+  "updatedAt": "'$(date -u +"%Y-%m-%dT%H:%M:%S.000Z")'"
+}'
+
+POST_RESPONSE=$(curl -s -X POST "$BACKEND_URL/api/snippets" \
+    -H "Origin: $FRONTEND_URL" \
+    -H "Content-Type: application/json" \
+    -d "$TEST_SNIPPET" \
+    -i)
+
+POST_HEADERS=$(echo "$POST_RESPONSE" | grep -i "access-control")
+POST_STATUS=$(echo "$POST_RESPONSE" | head -n 1)
+
+if echo "$POST_HEADERS" | grep -q "access-control-allow-origin"; then
+    echo "✅ POST request CORS successful"
+    echo "Status: $POST_STATUS"
+    echo "$POST_HEADERS"
+else
+    echo "❌ POST request CORS failed - missing CORS headers"
+    echo "Status: $POST_STATUS"
+fi
+echo ""
+
+# Test 5: Wrong Origin (Should fail or return no CORS headers)
+echo "🔍 Test 5: Request from Unauthorized Origin"
+echo "--------------------------------------"
+WRONG_ORIGIN="https://malicious-site.com"
+WRONG_HEADERS=$(curl -s "$BACKEND_URL/api/snippets" \
+    -H "Origin: $WRONG_ORIGIN" \
+    -i | grep -i "access-control")
+
+if [ -z "$WRONG_HEADERS" ]; then
+    echo "✅ Correctly blocking unauthorized origin"
+    echo "   (No CORS headers returned for $WRONG_ORIGIN)"
+elif echo "$WRONG_HEADERS" | grep -q "access-control-allow-origin.*\*"; then
+    echo "⚠️  Warning: Backend allows all origins (*)"
+    echo "   This is fine for development but should be restricted in production"
+else
+    echo "⚠️  Unexpected CORS response for unauthorized origin"
+    echo "$WRONG_HEADERS"
+fi
+echo ""
+
+# Summary
+echo "======================================"
+echo "Test Summary"
+echo "======================================"
+echo "Backend URL:  $BACKEND_URL"
+echo "Frontend URL: $FRONTEND_URL"
+echo ""
+echo "If all tests passed:"
+echo "  ✅ Your CORS configuration is working correctly"
+echo ""
+echo "If tests failed:"
+echo "  1. Verify backend is running at $BACKEND_URL"
+echo "  2. Check CORS_ALLOWED_ORIGINS environment variable"
+echo "  3. Ensure it includes $FRONTEND_URL"
+echo "  4. Restart backend after environment changes"
+echo "  5. See CORS-GUIDE.md for detailed troubleshooting"
+echo "======================================"