JWT Decoder

A JSON Web Token (JWT) is a compact, URL-safe token format used for securely transmitting claims between two parties. This JWT decoder lets you decode JWT tokens online and inspect their contents instantly. JWTs consist of three Base64URL-encoded parts separated by dots — a header, a payload, and a signature — and are widely used in authentication systems, OAuth 2.0 flows, API authorization, and single sign-on (SSO).

It is critical to understand that JWT is an encoding format, not encryption. Anyone with access to a token can decode the header and payload without needing a secret key. The header identifies the signing algorithm (e.g., HS256, RS256) and token type, while the payload carries claims such as user ID, roles, expiration time (exp), issued-at time (iat), and subject (sub). This JWT inspector displays every claim clearly and flags whether the token has expired.

Security matters when working with tokens. Many online JWT decode tools send your token to a remote server for processing, which risks leaking sensitive claims such as user IDs or session data. This JWT token decoder runs entirely in your browser using JavaScript — no data ever leaves your machine. Even so, avoid pasting production tokens into any online tool unless you are certain it is client-side only.

This tool pairs well with our Base64 Decode and Base64 Encode utilities for working with the raw Base64URL segments of a token, and our article on JWT Tokens Explained provides a deeper dive into token structure, signing algorithms, and best practices. Whether you are debugging an authentication flow, reviewing API responses, or learning how JWTs work, this free JSON web token decoder gives you the full picture in seconds.