JWT Decoder & Validator

What is a JWT Decoder?

A JWT decoder is a tool that parses and displays the contents of a JSON Web Token (JWT). JWTs are the most widely used authentication tokens in modern web applications: used by OAuth 2.0, OpenID Connect, and stateless REST APIs. They consist of three Base64URL-encoded parts: a header describing the algorithm, a payload containing claims (user data and metadata), and a signature for verification.

CodeHelper's JWT Decoder & Validator decodes tokens instantly and can verify HMAC signatures (HS256, HS384, HS512) entirely in your browser, so your tokens never leave your machine.

JWT Claims Explained

• exp: Expiration time: the token is invalid after this UNIX timestamp.
• iat: Issued at: when the token was created.
• sub: Subject: typically the user ID the token represents.
• iss: Issuer: the entity that created the token (e.g., your auth server URL).
• aud: Audience: the intended recipient(s) of the token.
• nbf: Not Before: the token is not valid before this time.

How to decode a JWT token

1. Paste your JWT token (starting with "eyJ...") into the input field.
2. The header and payload are decoded and displayed as formatted JSON instantly.
3. Review token claims, expiration status, and time remaining.
4. Optionally enter your HMAC secret to verify the signature.
5. Copy individual parts for use in debugging or documentation.

Whether you are debugging authentication issues, inspecting OAuth tokens, auditing API security, or learning how JWTs work, this free JWT decoder and validator is the most private and convenient tool available.