JWT Decoder

JWT Security Guide

Understanding JSON Web Tokens and their role in modern authentication.

JWT Structure

A JWT consists of three parts separated by dots:

  • Header: Algorithm and token type
  • Payload: Claims (user data, expiration, etc.)
  • Signature: Verifies token integrity

Security Best Practices

When working with JWTs:

  • Always validate the signature
  • Check expiration (exp claim)
  • Use HTTPS for transmission
  • Store tokens securely (not in localStorage)

JWT Example

Sample JWT Token

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyLCJleHAiOjE1MTYyMzkwMjJ9.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c
Note: This is a test token with the secret "your-256-bit-secret". Never use hardcoded secrets in production.