Inside the Token: Understanding JSON Web Tokens
A **JWT (JSON Web Token)** is a compact URL-safe means of representing claims to be transferred between two parties. Our decoder allows you to inspect the contents of any JWT instantly, revealing the user identity, expiration times, and algorithm details stored within the encoded dots.
The Header
Specifies the token type (JWT) and the signing algorithm (e.g., HS256 or RS256).
The Payload
Contains the "claims"—statements about a user (e.g., name, admin status) and metadata.
The Signature
Created by taking the encoded header & payload and a secret key to ensure the token hasn't been tampered with.
Security Check: 100% Local Decoding
JWTs often contain sensitive user IDs or scopes. SUDT's JWT Decoder runs entirely in your **local memory**. Your token is never transmitted to any server—not even our own. Debug with absolute peace of mind.