JWT Decoder

JWT (JSON Web Token) is a compact, URL-safe token used for authentication and information exchange. It consists of three Base64Url-encoded parts: header, payload, and signature.

Absolutely. Everything runs locally in your browser - your tokens never leave your computer. No data is uploaded to any server.

No. Decoding only extracts the readable header and payload — it does NOT verify the signature. For signature verification, you need the secret key (HS256) or public key (RS256/ES256) and a JWT library. Never trust unverified JWT claims.

The exp claim is the expiration time as a Unix timestamp. JWTs should be rejected after this time to prevent replay attacks. Always validate exp on the server side. The decoder shows exp as both a timestamp and a human-readable date for convenience.

Yes, but with caveats. JWTs are stateless — the server doesn't need to store session data. However, this means you can't invalidate individual tokens without a blocklist. For most web apps, traditional session cookies with server-side storage are simpler and more secure.

The header shows the token type and signing algorithm. The payload contains claims like issuer, subject, expiration time, and custom data. The signature is shown in raw form.