Paste any JWT token and instantly decode the header, payload, and check expiry — no private key needed, runs entirely in your browser.
Also encode and decode data with our Base64 Encoder or test patterns with the Regex Tester.
🔒 Your token is processed locally — it is never sent to any server or stored anywhere.
A JWT (JSON Web Token) is a compact, URL-safe token format used to securely transmit information between parties as a JSON object. It consists of three Base64-encoded parts separated by dots: the Header (algorithm and token type), the Payload (claims and data), and the Signature (cryptographic verification). This JWT decoder tool works as a JWT parser, JWT inspector, and token claim viewer for developers debugging authentication flows.
Developers use JWT decoders constantly during API development and debugging. When an API returns a 401 Unauthorized response and you suspect the token may be expired or contain incorrect claims, decoding it instantly reveals the payload without needing to write a script or make a server call. You can see the exact expiry timestamp, the issued-at time, the user ID, roles, and any custom claims — all in plain JSON in seconds.
Front-end developers use JWT decoders to verify that the authentication token stored in localStorage or a cookie contains the expected user data before making API calls. If the user's role claim is missing or incorrect, that explains why certain UI elements are not appearing or certain API routes are returning permission errors. Reading the payload here confirms what the token actually contains versus what the application expects.
Security engineers and QA testers use JWT decoders to audit tokens during penetration testing and security reviews — checking that tokens include appropriate expiry windows, that sensitive data is not unnecessarily stored in the payload (since JWT payloads are only Base64-encoded, not encrypted), and that the algorithm claim matches the expected signing algorithm. The tool shows the exact alg field, making it easy to spot weak algorithms like none or HS256 where RS256 was expected.