JWT Debugger

What this tool does

JWT Debugger helps you decode and analyze JSON Web Tokens used in authentication and API security. It breaks a token into its header, payload, and signature, allowing you to clearly see claims, expiration time, issuer details, and signing algorithm.

This tool is designed for developers who need quick visibility into JWT contents while debugging login failures, authorization issues, or token validation errors. Instead of manually decoding base64 strings, you can inspect everything in a readable format instantly.

How to use this tool

• Paste the JWT token into the input field.
• Provide a secret or public key if verification is required.
• Select the appropriate signing algorithm.
• Click decode to analyze the token.
• Review the decoded header, payload, and signature status.

Common use cases

• Debug API authentication and authorization failures.
• Inspect JWT claims such as user ID, roles, and permissions.
• Check token expiration and time-based issues.
• Verify HS256 or RS256 signatures during development.
• Analyze OAuth or OpenID Connect access tokens.
• Validate tokens exchanged between microservices.
• Confirm claim changes after regenerating tokens.

Tips and limitations

• JWT payloads are readable and not encrypted.
• Always validate tokens on the server in production.
• Signature verification requires the exact secret or public key.
• Expired tokens will fail validation even with a valid signature.
• Avoid using sensitive production tokens in shared environments.
• This tool is intended for debugging, not token generation.

FAQ

What is a JSON Web Token (JWT)?

A JWT is a compact, URL-safe token used to securely transmit information between systems. It consists of a header, payload, and signature and is commonly used for authentication and authorization.

Is JWT data encrypted?

No. JWT payloads are only base64 encoded, not encrypted. Anyone with access to the token can read its contents, but cannot modify it without invalidating the signature.

Does this tool store my tokens?

No. Tokens are processed only for decoding and verification. They are not stored, logged, or shared by the tool.

Why does my token show an invalid signature?

This usually happens when the wrong secret, public key, or signing algorithm is used. Even small mismatches will cause verification to fail.

What causes a JWT token to expire?

JWT expiration is controlled by the exp claim. Once the expiration time passes, the token becomes invalid and should no longer be accepted by the server.

Which JWT algorithms are supported?

Common algorithms such as HS256 and RS256 are supported. Verification depends on providing the correct key and matching algorithm.