Understanding JWT Authentication

JSON Web Tokens Explained

JWT (JSON Web Token) is a compact, URL-safe means of representing claims between two parties. It's become the standard for API authentication.

JWT Structure

A JWT consists of three parts separated by dots:

• Header - Algorithm and token type
• Payload - Claims (data)
• Signature - Verification signature

How JWT Works

1. User logs in with credentials
2. Server verifies credentials and creates JWT
3. Client stores JWT (usually in localStorage or httpOnly cookie)
4. Client sends JWT in Authorization header for protected requests
5. Server verifies JWT and processes request

Implementing JWT in Node.js

Use the jsonwebtoken library to create and verify tokens:

const jwt = require('jsonwebtoken');

// Create token
const token = jwt.sign({ userId: user.id }, process.env.JWT_SECRET, { expiresIn: '24h' });

// Verify token
const decoded = jwt.verify(token, process.env.JWT_SECRET);

Security Best Practices

• Use strong, random secrets
• Set appropriate expiration times
• Store secrets securely
• Implement refresh tokens for long-lived sessions
• Use HTTPS in production
• Consider token blacklisting for logout

JWT vs Session-based Authentication

JWT offers stateless authentication but comes with trade-offs in terms of token size and revocation complexity.