JSON Web Tokens (JWT) have become the standard for modern web authentication. Learn how they work and best practices for implementation.
What is JWT?
A JWT is a compact, URL-safe token format that contains claims about a user. It consists of three parts separated by dots:
- Header - Algorithm and token type
- Payload - Claims (user data, expiration, etc.)
- Signature - Verification hash
How JWT Authentication Works
The typical JWT authentication flow:
- User logs in with credentials
- Server validates and creates a JWT
- Client stores the JWT (localStorage/cookie)
- Client sends JWT with each request
- Server validates JWT and processes request
Security Best Practices
Always use HTTPS, set short expiration times, and implement token refresh mechanisms.
Common Claims
- iss - Issuer of the token
- sub - Subject (user ID)
- exp - Expiration time
- iat - Issued at time
- aud - Audience (intended recipient)
JWT vs Sessions
JWTs are stateless and scalable, while sessions require server-side storage. Choose based on your application's needs.