JSON Web Token Decoder
Decode the header and payload of a JWT (JSON Web Token) securely in your browser.
Key Capabilities
Decodes header, payload, and signature separately
The decoder splits and presents each section in a formatted, readable JSON view.
Token expiry and validity status
The tool checks the exp claim against the current time and displays whether the token is valid or expired.
Processes entirely in-browser for security
JWT tokens are decoded entirely in the browser using local JavaScript — the token never leaves your device.
How to Use
Paste your JWT
Copy the JWT token from your browser developer tools or API testing tool. Paste the full token.
Review the decoded sections
Check the header for signing algorithm and the payload for all claims.
Check expiry status
The expiry status banner shows whether the token is currently valid or expired.
Common Use Cases
- Developers debugging authentication failuresA developer can check whether the token has expired or whether the correct claims are present.
- Security engineers auditing JWT claimsA security engineer can verify that sensitive data is not being embedded unnecessarily in the payload.
- QA engineers verifying token contentsA QA engineer can verify that correct user ID, roles, and permissions are present in each token.
Frequently Asked Questions
What is a JWT and why decode it?
A JWT (JSON Web Token) is a Base64-encoded token used for authentication and authorization in web applications. Decoding it reveals the header (algorithm info), payload (user claims, expiration, permissions), and allows developers to debug authentication issues without verifying the signature.
Who uses this tool professionally?
Backend developers debug authentication failures by inspecting JWT payload claims. Security auditors review JWT tokens for sensitive data exposure and weak algorithm usage. QA engineers verify that correct user roles and permissions are encoded in API authentication tokens.
Does it verify the JWT signature?
No. This tool decodes and displays the header and payload for inspection purposes only. Signature verification requires the signing secret or public key, which should never be entered into a web tool. Use your application's JWT library for signature verification.
Is my JWT kept private?
Yes. All decoding happens locally in your browser. JWT tokens containing authentication credentials and user claims are never transmitted to any server.
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