What is a JWT and how does the decoder work?

A JSON Web Token (JWT) is a compact, URL-safe means of representing claims between two parties. The decoder extracts and decodes the base64url-encoded header and payload sections, displaying them as readable JSON. The signature section cannot be verified without the secret key.

Is it safe to decode JWT tokens with this tool?

Yes, the JWT decoder is completely safe and private. All decoding happens locally in your browser - no JWT data is transmitted to external servers. This ensures your tokens remain secure and private throughout the decoding process.

Why can't the signature be verified?

JWT signature verification requires the secret key that was used to sign the token. Since this tool is client-side only and focused on decoding (not authentication), signature verification is not performed. The tool focuses on decoding header and payload information only.

What JWT claims are supported and displayed?

The decoder supports all standard JWT claims including iss (issuer), sub (subject), aud (audience), iat (issued at), exp (expires), and any custom claims present in the payload. Special formatting is provided for common timestamp and identifier claims.

What format should my JWT token be in?

Your JWT token should be in the standard format with three segments separated by dots: header.payload.signature. Each segment should be base64url encoded. The tool will validate the format and provide helpful error messages for malformed tokens.

Can I decode expired JWT tokens?

Yes, you can decode expired JWT tokens. The decoder will show the expiration timestamp and indicate that the token has expired, but will still decode and display the header and payload information for analysis and debugging purposes.

JWT Decoder

Decode and inspect JSON Web Tokens (JWT) instantly with header and payload analysis, claim validation, and security-focused design. Perfect for debugging authentication, API development, and security auditing with comprehensive error handling and example tokens.

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Try these example JWT tokens to see the decoding process

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Enter your JWT token to decode header and payload information

How it works: Decodes the JWT header and payload from base64url encoding and displays the JSON content. Only decoding is performed — signature verification requires the secret key and is not done. All processing happens locally in your browser.

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