JWT Decoder

The JWT Decoder decodes and inspects JSON Web Tokens without needing any secret key or server call. JWTs are used extensively in modern authentication systems — every time you log in to an application that uses OAuth, OpenID Connect, or stateless authentication, you likely receive a JWT in response.

To use it, paste the JWT into the input field. The tool automatically splits the token into its three parts — header, payload, and signature — and decodes the header and payload into readable JSON. You will immediately see information such as the signing algorithm used, the subject (user identifier), permission scopes, issuance and expiration dates, and any custom claims the application included.

The tool also checks whether the token is expired by comparing the 'exp' field against the current time on your device. This is extremely useful during development to understand why a request is failing with a 401: often the token has simply expired.

Important: this tool does not validate the token signature. It only decodes the public content. To verify that a token is genuine, you need to check the signature against the secret key on the server side. No data is sent outside the browser — the base64 decoding happens entirely on the client side.