Second Brain App

Second Brain is a full-stack TypeScript monorepo (React frontend + Express backend) for personal knowledge management. Save links, articles, videos and notes; organize them into multiple “brains,” tag and search items, auto-extract URL metadata, and share public collections via unique links. Built with MongoDB, JWT auth, TailwindCSS and TypeScript for a reliable, developer-friendly foundation.

🚀 Quick Start

1. Install dependencies

   npm install

2. Set up environment

   cp packages/server/.env.example packages/server/.env
   # Edit .env with your MongoDB URI and JWT secret

3. Start development

   npm run dev

   This starts both the server (port 5000) and client (port 3000) concurrently.

📁 Project Structure

second-brain/
├── packages/
│   ├── server/           # Express.js backend
│   │   ├── src/
│   │   │   ├── models/   # MongoDB schemas
│   │   │   ├── routes/   # API endpoints
│   │   │   └── middleware/
│   │   └── package.json
│   └── client/           # React frontend
│       ├── src/
│       │   ├── components/
│       │   ├── contexts/
│       │   └── main.tsx
│       └── package.json
└── package.json          # Workspace root

🛠 Tech Stack

Backend:

• Node.js + Express
• TypeScript
• MongoDB + Mongoose
• JWT Authentication
• bcrypt for password hashing
• Automatic URL metadata extraction

Frontend:

• React 18
• TypeScript
• Tailwind CSS
• React Router
• Axios for API calls
• Lucide React icons

🔥 Features

• Authentication: Register/login with JWT
• Multiple Brains: Organize content into different collections
• Content Types: Links, articles, videos, notes
• Auto Metadata: Automatic title/description extraction from URLs
• Safety Moderation: Groq AI checks shared content safety
• Age Restriction: Unsafe content is automatically marked 18+
• Source Health: Shared links show "Source Deleted" if unreachable
• Search & Filter: Full-text search and type filtering
• Tags: Organize items with custom tags
• Sharing: Share brains publicly with unique URLs
• Responsive: Works on desktop and mobile

🌐 API Endpoints

Auth

• POST /api/auth/register - Create account
• POST /api/auth/login - Sign in

Brains

• GET /api/brains - Get user's brains
• POST /api/brains - Create new brain
• POST /api/brains/:id/share - Generate share link
• GET /api/brains/shared/:token - View shared brain

Items

• GET /api/items - Get items (with search/filter)
• POST /api/items - Add new item
• PUT /api/items/:id - Update item
• DELETE /api/items/:id - Delete item

🚢 Deployment

Environment Variables

# Server (.env)
PORT=5000
MONGODB_URI=mongodb://localhost:27017/second-brain
JWT_SECRET=your-super-secret-jwt-key
GROQ_API_KEY=your-groq-api-key
GROQ_MODERATION_MODEL=llama-3.1-8b-instant

# Client (packages/client/.env)
VITE_API_BASE_URL=/api
VITE_GOOGLE_CLIENT_ID=your-google-client-id

Build & Deploy

# Build for production
npm run build

# Start production server
npm start

Chrome Extension

A Chrome extension is available at packages/extension for one-click capture.

Load In Chrome

1. Go to chrome://extensions
2. Enable Developer mode
3. Click Load unpacked
4. Select packages/extension

Setup

1. Start backend: npm run dev
2. Open extension popup and set API URL (default http://localhost:5000/api)
3. Login with your Second Brain account
4. Select default brain
5. Click Add to Brain on any webpage