JWT Decoder
Paste a JSON Web Token to decode its header and payload. Everything runs locally in your browser.
Token
Your JWT is decoded entirely in your browser using atob() and JSON.parse(). No tokens are ever transmitted to or stored on our servers.
About JSON Web Tokens
JWTs are the most common token format for web authentication. They consist of three Base64URL-encoded parts separated by dots:
eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxMjM0NTY3ODkwIn0.SflKxwRJSMeKKF2QT4fw...
- Header: Algorithm and token type (e.g., HS256, RS256)
- Payload: Claims — the data (user ID, roles, expiration)
- Signature: Proves the token hasn't been tampered with