Is my JWT token secure when using this decoder?

Yes, absolutely. All decoding and verification happens entirely in your browser using SubtleCrypto. Your tokens and secret keys never leave your machine or reach our servers.

What JWT algorithms does this tool support for verification?

The tool supports HMAC algorithms: HS256, HS384, and HS512. RSA and ECDSA tokens can be decoded to view their contents but cannot be verified without a public key.

Why does my token show as expired?

The 'exp' claim contains a Unix timestamp in seconds. If this timestamp is earlier than the current time, the token has expired and will be rejected by most authentication systems.

Can I verify JWT tokens without providing a secret key?

You can decode any JWT to view its header and payload without a secret key. However, signature verification requires the appropriate secret key or public key depending on the algorithm used.

What should I do if my JWT signature verification fails?

Check that you're using the correct secret key, verify the algorithm matches what was used to sign the token, and ensure there are no extra spaces or characters in your inputs.

JWT Decoder & Verifier - Free Online JSON Web Token Tool

The JWT Decoder & Verifier is a comprehensive online tool designed to decode and verify JSON Web Tokens (JWTs) directly in your browser. This powerful utility allows developers, security professionals, and system administrators to inspect JWT payloads, validate token integrity, and troubleshoot authentication issues without compromising security or privacy.

Key Features and Usage

This JWT decoder supports complete token analysis by parsing the header, payload, and signature components of any JSON Web Token. The tool automatically decodes base64-encoded sections to reveal readable JSON data, making it easy to examine claims, expiration times, and token metadata. For JWT verification, the tool supports HMAC algorithms including HS256, HS384, and HS512, allowing you to validate token signatures using your secret key. Simply paste your JWT into the decoder, and optionally provide your secret key for signature verification.

Security and Best Practices

Security is paramount when working with JWTs. This tool processes all tokens entirely within your browser using the SubtleCrypto API, ensuring that tokens never leave your machine or reach external servers. When using the verification feature, always use strong, randomly generated secret keys and rotate them regularly. Pay attention to the exp (expiration) claim to ensure tokens haven't expired, as expired tokens will be rejected by most authentication systems.

Benefits for Developers

This JWT debugger streamlines the development and debugging process by providing instant token analysis without requiring additional software installation. Whether you're implementing OAuth flows, debugging API authentication, or auditing security tokens, this tool offers a quick and secure way to inspect JWT structure and validate token integrity while maintaining complete privacy and security.

JWT Decoder & Verifier - Free Online JSON Web Token Tool