JWT Token Decoder
Decode JSON Web Tokens (JWT) locally in your browser. Inspect headers, payload, and signatures.
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Your files never leave your computer — processed in-browser with WebAssembly.
No queues, no uploads — results in milliseconds, even on mobile.
Clean interface, dark mode, and no popups — built to beat legacy tools.
What you get
- Decode JWT header and payload
- Check token expiration status
- No data sent to the server
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Frequently asked questions
A JWT is an open standard (RFC 7519) that defines a compact and self-contained way for securely transmitting information between parties as a JSON object. They are commonly used for authentication and authorization.
No. Our JWT Decoder parses the token entirely on the client-side using JavaScript. Your token is never transmitted to our servers, keeping your sensitive session data safe.
A JWT consists of three parts separated by dots: Header (algorithm and token type), Payload (the data or claims), and Signature (used to verify the token hasn't been altered).
No, this tool only decodes the Base64-encoded Header and Payload so you can read the data. Verifying the signature requires the private secret key, which should never be exposed to a public tool.
It reads the `exp` (expiration time) claim from the decoded payload. The `exp` value is a Unix timestamp. The tool compares it to your computer's current time to determine if it has expired.
A valid JWT must have exactly three base64-encoded segments separated by two dots (`.`). Ensure you haven't accidentally copied extra whitespace or missed a portion of the token.
Currently, this tool is a decoder only. You cannot forge a valid JWT without the server's private secret key, as altering the payload will invalidate the signature.
The `sub` (Subject) claim usually contains a unique identifier for the user or entity that the token belongs to, such as a user ID or email address.
The `iat` (Issued At) claim is a Unix timestamp that identifies the exact time the JWT was generated by the server.
No. The header and payload of a standard JWT are merely Base64 encoded, not encrypted. Anyone who captures the token can decode it and read the data. Sensitive information should never be put in the payload.