What is a JWT?
A JSON Web Token (JWT) is a compact, URL-safe way to represent claims between two parties. The token has three Base64URL-encoded parts separated by dots: a header, a payload, and a signature. Developers use JWTs for API authentication, session handoff, and service-to-service trust.
How this decoder works
Cyberway decodes the header and payload in your browser with no network round-trip for the token itself. You can inspect registered claims such as iss, sub, aud, and exp, see whether the token is expired, and optionally verify the signature with a shared secret or public key. Because processing stays on-device, you can debug real tokens without sending them to a third-party server.
Security notes
Decoding is not the same as trusting a token. Always verify signatures on your server, reject alg: none, and avoid weak HMAC secrets. Use this tool to understand what a token contains — then validate it in your application with production-grade key management.
Need to create a token for local testing? Try the JWT Generator. For deeper reading, start with the Complete JWT Guide.