JWT is an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. It's widely used for authentication and information exchange in web applications.

Key Components of JWT 📦

JWT consists of three parts:

  1. Header 🔐

    • Contains metadata like token type and signing algorithm
      JWT_Header

  2. Payload 📄

    • Holds the actual data (claims)
    • Example claims: sub (subject), exp (expiration time), iat (issue time)
      JWT_Payload

  3. Signature ⚙️

    • Verifies token integrity using the header and payload
    • Generated via: HMACSHA256(base64UrlEncode(header) + "." + base64UrlEncode(payload), secret_key)
      JWT_Signature

Common Use Cases 🌐

  • API Authentication 🔄
    GET /api/data requires valid JWT in Authorization header
  • Single Sign-On (SSO) 🎒
    Cross-domain session management through token sharing
  • User Information Exchange 📱
    Securely transfer user data between services
    OAuth2_JWT

Security Best Practices ⚠️

✅ Always use HTTPS
✅ Prefer HS256 or RS256 signing algorithms
✅ Set appropriate token expiration times
✅ Store tokens securely (never in local storage!)
⚠️ Avoid including sensitive data in payload

Related Resources 📚

Learn about OAuth2 implementation
View JWT validation code examples
JWT.io official documentation 🔗

Note: This guide follows the IETF standard for JWT format and usage