JWT Decoder & Validator

JSON Web Tokens (JWT) have become the de facto standard for secure authentication and information exchange in modern web applications. These tokens are particularly useful in microservices architectures, single sign-on (SSO) implementations, and API authentication scenarios. Each JWT consists of three distinct parts encoded in base64: the header, payload, and signature.

The header typically contains information about the type of token and the algorithm used for signing, such as HS256 or RS256. The payload carries the actual data, known as claims, which can include user information, permissions, and token metadata. The signature, created using a secret key, ensures the token hasn't been tampered with during transmission.

When implementing JWT authentication, it's crucial to handle token expiration properly. Short-lived tokens (usually 15-60 minutes) are recommended for access tokens, while longer-lived refresh tokens can be used to obtain new access tokens. Always validate tokens on the server side, check for proper signature verification, and never store sensitive information like passwords or credit card details in the token payload.

Common security considerations include protecting against XSS attacks by storing tokens securely (preferably in HTTP-only cookies), implementing proper CORS policies, and using strong encryption keys. For high-security applications, consider implementing token revocation mechanisms and keeping track of issued tokens.