JWT Decoder & Builder

Decode JSON Web Tokens (JWT) instantly, or securely construct and sign new HS256 authentication tokens offline.

Encoded Token

Header

{
  "alg": "HS256",
  "typ": "JWT"
}

Payload

{
  "sub": "1234567890",
  "name": "John Doe",
  "iat": 1516239022
}

Secret Key (HS256)

How to Decode and Sign JWTs

Paste an encoded JWT string to view its decoded header and payload data. You can also modify the header/payload, enter a secret key, and securely generate a newly signed HS256 token directly in your browser. Since it runs client-side, your secret keys are never transmitted.

What is a JSON Web Token (JWT)?

JSON Web Tokens are an open, industry-standard (RFC 7519) method for representing claims securely between two parties. They are heavily used in modern web applications for stateless authentication and single sign-on (SSO) architectures.

Secure Local Token Generation

Most online JWT debuggers send your token or your secret key to a remote server. This is a massive security risk. This tool uses the native Web Crypto API to sign HS256 tokens locally. You can safely paste production tokens or secret keys knowing they will never leave your browser.