Just Between Us - Shhh...it's just between us.

Create a private chat room, share the link, and chat. The room disappears after 10 minutes (or you can destroy it manually). All messages are encrypted client-side using AES-256-GCM - the server never sees your encryption keys or plaintext messages.

✨ Features

📡 Real-Time

• Instant Message Delivery - Real-time messaging powered by Upstash Realtime
• Live Updates - Messages appear instantly without page refresh
• WebSocket Communication - Efficient bidirectional communication

⚡ Performance

• Serverless Infrastructure - Scales automatically with Upstash Redis and Realtime
• Efficient Real-Time - WebSocket-based messaging with minimal latency
• Robust Backend - Bun-first web framework with exceptional performance.
• Bun Runtime - Ultra-fast JavaScript runtime with native TypeScript support, faster startup times, and optimized package management
• React Compiler - Automatic memoization and optimization, eliminating manual useMemo, useCallback, and React.memo
• Turbopack - Rust-powered bundler from Vercel, up to 700x faster than Webpack for incremental builds

🎨 UI/UX

• Modern Minimal Interface - Clean, distraction-free design built with Tailwind CSS 4
• Progressive Web App (PWA) - Installable app with offline support and service worker caching
• Intuitive Navigation - Simple, straightforward user flow
• Fully Responsive - Works seamlessly across all devices and screen sizes
• Enhanced Error Handling - Clear error messages for room not found, room full, and encryption key issues

👨‍💻 Developer Experience

• End-to-End Type Safety - Type-safe API calls with Elysia and Eden
• Runtime Validation - Zod schemas ensure data integrity at runtime
• Clean Architecture - Well-organized codebase with separation of concerns

🔐 Security

• True End-to-End Encryption - Messages encrypted client-side with AES-256-GCM. Only participants can read messages, even if the server is compromised
• Secure Key Sharing - Encryption keys shared via URL fragments (never sent to server)
• Zero-Knowledge Architecture - Server never sees encryption keys or plaintext messages
• Client-Side Key Management - Encryption keys never leave the browser, stored only in memory
• Anonymous Identity - Auto-generated usernames for privacy with regeneration support
• No Persistent User Data - No user accounts, tracking, or data collection
• Room Isolation - Complete data separation between rooms with token-based authentication
• Self-Destructing Rooms - Automatic room expiration after 10 minutes with manual destroy option
• Automatic Data Expiration - Rooms and messages auto-delete after expiration
• Authenticated Encryption - AES-GCM provides message authentication and tamper detection

📊 Project Flow Diagram

Diagram: Just Between Us app architecture, encryption, and real-time flow.

🔗 View Interactive Flow Diagram on tldraw

🛠️ Tech Stack

Frontend

• Next.js 16.1 - React framework with App Router
• React 19.2 - Latest React with React Compiler
• Tailwind CSS 4 - Modern utility-first CSS framework
• TanStack Query - Powerful data synchronization for React

Backend & Infrastructure

• Elysia - Fast, type-safe web framework (Bun runtime)
• Upstash Redis - Serverless Redis for data persistence
• Upstash Realtime - Real-time messaging infrastructure
• Zod - TypeScript-first schema validation

Development Tools

• TypeScript 5.0 - Type-safe development
• Turbopack - Next-generation bundler for fast development
• ESLint - Code linting and quality
• React Compiler - Automatic React optimization
• Bun - Fast JavaScript runtime and package manager
• Serwist - Service worker library for PWA functionality and offline support

🚀 Getting Started

Prerequisites

• Node.js 18+ or Bun (recommended)
• Upstash Redis account (free tier available)

Installation

1. Clone the repository

   git clone <repository-url>
   cd justbetweenus

2. Install dependencies

   bun install
   # or
   npm install

3. Set up environment variables

   Create a .env.local file in the root directory:

   UPSTASH_REDIS_REST_URL=your_redis_url
   UPSTASH_REDIS_REST_TOKEN=your_redis_token

4. Run the development server

   bun dev
   # or
   npm run dev

5. Open your browser

   Navigate to http://localhost:3000

🔑 How End-to-End Encryption Works

Just Between Us uses true end-to-end encryption to ensure your messages remain private. All encryption happens client-side using the browser's Web Crypto API - no external dependencies required.

Key Features

• AES-256-GCM Encryption - Industry-standard authenticated encryption
• Zero-Knowledge Architecture - Server never sees encryption keys or plaintext messages
• Secure Key Exchange - Keys shared via URL fragments (never transmitted to server)
• Unique IV per Message - Each message uses a random initialization vector for forward secrecy
• Client-Side Only - All encryption/decryption happens in your browser

For a detailed explanation of the encryption flow, key generation, message encryption, and security guarantees, see the End-to-End Encryption Documentation.

📄 License

This project is open source and available under the MIT License.

🤝 Contributing

Contributions, issues, and feature requests are welcome! Feel free to check the issues page.

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Built with ❤️ using Next.js, React, and modern web technologies