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What Is JWT Decoder?
JWT Decoder is a free online jwt decoder that lets you inspect JSON Web Tokens instantly. Paste any JWT to see its decoded header, payload, and signature details without installing any software.
Key Features
Decode JWT tokens in real time as you paste. View header with algorithm and token type. Inspect payload claims including expiration, issuer, and custom data. Timestamps are automatically converted to human-readable dates. Syntax-highlighted JSON output for easy reading.
Benefits of Decoding JWTs
Understanding what is inside a JWT helps you debug authentication issues, verify token claims, and check expiration times. This is essential during API development, OAuth integration, and troubleshooting login flows in web and mobile applications.
Common Use Cases
Debug authentication failures by checking token expiration. Verify user roles and permissions stored in JWT claims. Inspect tokens received from third-party OAuth providers. Validate that tokens contain the expected data before deploying to production.
JWT Security Tips
Never store JWTs in localStorage for sensitive applications; use httpOnly cookies instead. Always validate tokens on the server side. Set short expiration times and use refresh tokens. Never include sensitive data like passwords in JWT payloads since they are only encoded, not encrypted.
Frequently Asked Questions
A JSON Web Token (JWT) is a compact, URL-safe token used for authentication and information exchange. It consists of three parts: a header, a payload, and a signature, each separated by dots and Base64-encoded.
This tool decodes and displays the header and payload of a JWT token. It shows the signature algorithm used but does not verify the signature, since that requires the secret key or public key.
Yes. All decoding happens locally in your browser. Your token is never sent to any server. However, avoid sharing JWT tokens publicly as they may contain sensitive user information.
You can see the algorithm and token type in the header, and claims like user ID, email, roles, issued-at time, and expiration time in the payload. The exact fields depend on what the issuer included.
This tool focuses on decoding and inspecting tokens. Re-encoding a valid JWT requires signing it with the correct secret key, which is a server-side operation for security reasons.