Generate output instantly with JWT Decoder. Customizable options and one-click copy.
Paste a JWT token.
Header, payload, and signature are decoded.
View claims, expiration, and token details.
A JSON Web Token (JWT) is a compact, URL-safe token format used for securely transmitting information between parties as a JSON object. It consists of three Base64-encoded parts: a header (algorithm and type), a payload (claims and data), and a signature (integrity verification). JWTs are widely used for authentication, authorization, and secure API communication.
The decoder extracts and displays the signature portion of the JWT, but actual cryptographic verification requires the secret key (for HMAC) or public key (for RSA/ECDSA). Without the signing key, you can inspect the token contents but cannot confirm its authenticity. This is by design — signature verification should happen server-side.
Yes, all JWT decoding happens entirely in your browser using client-side JavaScript. No tokens are ever transmitted to any server, ensuring complete privacy for your authentication tokens. This is critical because JWTs often contain sensitive user claims, session data, and authorization scopes that should never be exposed to third parties.
