In the world of web applications, authentication is not just about login and logout — it’s about security, identity, trust, and system integrity.
In this article, we’ll walk through how I built a secure React-based authentication system with advanced features like:
- OTP & password manager
- One-device login logic
- Session management
- Device IP, OS, browser detection
All implemented using a frontend-only architecture (no backend APIs) — perfect for POCs, prototypes, and security-focused frontends.
📦 Source Code
The full codebase for this project is available on Gitlab
Feel free to explore the code, clone it, and try it out locally. Contributions and suggestions are welcome!
🔐 Key Features Covered
1. OTP Manager
- Generates and validates OTPs on the frontend
- Uses browser storage securely
- Includes resend limit and expiration timer
2. Password Manager
- Local password strength checker
- Encrypted storage using browser crypto APIs
- Shows real-time feedback on user input
3. Session & One-Device Login
- Allows only one active session per user
- New login revokes previous session automatically
- Simulates backend using in-memory logic
4. Device Detection
- Collects:
- Device IP
- Browser & version
- OS & version
- Device type (mobile, desktop, tablet)
This is useful for logging, analytics, and conditional auth flows.
⚙️ Tools & Libraries Used
- React (with hooks and functional components)
- TypeScript
- UAParser.js (for detecting browser, OS, and device info)
- CryptoJS (for hashing and secure storage)
- TailwindCSS (for UI styling)
🚧 Challenges Faced
- Managing security fully on the frontend
- Ensuring session persistence across tabs
- Avoiding overengineering while still demonstrating real-world complexity
- Keeping UX clean with all security prompts
🧠 Key Learnings
- Frontend-only auth is doable (for POCs), but always layer with a backend for production.
- Thinking like an attacker helps design better defensive mechanisms.
- React provides all the flexibility to modularize auth flows cleanly.
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📝 Originally published on Medium
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