JWT Decoder & Security Inspector

Our JSON Web Token (JWT) Decoder & Security Inspector provides client-side parsing, syntactic validation, and claim inspection for tokens strictly adhering to RFC 7519 and RFC 7515 (JWS) standards. Every token is processed 100% in local memory using native Web APIs. Zero credentials, bearer headers, or user identity claims are ever dispatched across the network.

JWT Architecture & RFC 7519 Standards

A standard JSON Web Token consists of three base64url-encoded components joined by periods (.): Header, Payload, and Signature.

1. Header (JOSE Header): Defines the cryptographic envelope, specifying the signing algorithm (alg, e.g., HS256, RS256) and media type (typ: "JWT").
2. Payload (Claims Set): The verifiable body of statements about an entity (typically the user) and additional metadata. Divided into registered claims, public claims, and private application claims.
3. Cryptographic Signature: A binary digest produced by signing the serialized header and payload using a secret key or asymmetric private key. Proves non-repudiation and prevents unauthorized payload alteration.

Registered Claims Reference (RFC 7519 Section 4.1)

Cryptographic Signing Algorithm Comparison

Developer Verification Code Snippets

1. Node.js & TypeScript (jsonwebtoken)

import jwt from 'jsonwebtoken';

export function verifyUserToken(token: string, secretKey: string) {
  return jwt.verify(token, secretKey, {
    algorithms: ['HS256'],
    issuer: 'https://auth.x114.org',
    audience: 'x114-api'
  });
}

2. Python 3 (PyJWT)

import jwt

def authenticate_request(bearer_token: str, public_pem: str) -> dict:
    return jwt.decode(
        bearer_token,
        public_pem,
        algorithms=["RS256"],
        audience="x114-api"
    )

3. Go (github.com/golang-jwt/jwt/v5)

package auth

import "github.com/golang-jwt/jwt/v5"

func ValidateToken(tokenString string, hmacSecret []byte) (*jwt.MapClaims, error) {
	token, err := jwt.Parse(tokenString, func(t *jwt.Token) (interface{}, error) {
		return hmacSecret, nil
	})
	if err != nil || !token.Valid {
		return nil, err
	}
	claims := token.Claims.(jwt.MapClaims)
	return &claims, nil
}