JWT decoder for headers, payloads and token claims

What is JWT Decoder?

A JWT decoder reads the Base64URL-encoded header and payload of a JSON Web Token so claims become visible.

Main use case: Decode a JWT to inspect claims such as exp, iat, sub, aud, issuer or custom API fields.

Common use cases

API debugging

Read token claims while investigating authentication issues.

Expiration checks

Inspect exp, iat and nbf timestamps before testing access flows.

Auth documentation

Prepare readable token examples for integration notes.

How to use the tool

1. Paste the JWT token.
2. Inspect the decoded header and payload.
3. Optionally enter a HS256 secret for testing.
4. Review status messages before using the token.

Best practices

• Use realistic test values when validating forms, exports or API payloads.
• Keep real customer, banking and production secrets out of public tools.
• Check the output format before copying it into a production workflow.
• Document whether a value is generated, validated, converted or only estimated.

Common mistakes

Confusing valid format with real-world validity

A generated or locally validated value can match a format without proving that it exists in an official system.

Using real production data

Public utilities are best for test data, demos, fixtures, QA and quick checks, not for confidential values.

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