DevToolKit

JWT Decoder | JSON Web Token Parser - DevToolKit

Free JWT decoder and parser. Decode JSON Web Tokens to inspect header, payload, and signature. Verify token expiration and claims.

What is JWT Decoder?

JWT Decoder is a free online tool that parses and decodes JSON Web Tokens. A JWT is a compact, URL-safe token format used for securely transmitting information between parties. It consists of three Base64URL-encoded parts separated by dots: header, payload, and signature. This tool lets you inspect all three parts without any server-side processing.

How to Use JWT Decoder

Paste a JSON Web Token (JWT) into the input field. The tool will instantly decode and display the header, payload, and signature sections. The header shows the algorithm and token type. The payload reveals all claims including issuer (iss), subject (sub), audience (aud), expiration (exp), and issued-at (iat) timestamps. Expiration status is shown automatically.

How JWT Decoder Works

A JWT consists of three parts separated by dots: header.payload.signature. The tool splits the token on the dot separator, then Base64URL-decodes the header and payload parts and parses them as JSON. The signature remains as a hex string. The tool also checks the exp (expiration) claim against the current time to show whether the token has expired.

Common Use Cases

  • Debugging authentication issues in web applications
  • Inspecting JWT claims and expiration times during API development
  • Verifying token payloads before sending them to an API
  • Learning how JWTs are structured and what claims they contain
  • Checking if a JWT has expired or contains expected fields

Frequently Asked Questions

What is a JWT?▼

A JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. It is commonly used for authentication and authorization in web APIs. A JWT has three parts: a header (algorithm info), a payload (claims), and a signature.

Can this tool verify a JWT signature?▼

This tool decodes and displays the signature but does not verify it, as verification requires the secret key or public key used to sign the token. It is designed for inspecting token contents, not for cryptographic validation.

Is it safe to paste my JWT here?▼

Yes. All decoding happens entirely in your browser. No data is sent to any server. However, never share JWTs publicly as they may contain sensitive information.

What are common JWT claims?▼

Common claims include iss (issuer), sub (subject), aud (audience), exp (expiration time), iat (issued at), nbf (not before), and jti (JWT ID). Custom claims can also be added by the token issuer.

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