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JWT Decoder

Decode and inspect JSON Web Tokens

Important: This tool decodes JWT tokens but does NOT verify signatures. Do not use for security decisions. All processing happens client-side.

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Understanding JWT Structure

A JWT has three parts separated by dots: Header.Payload.Signature

Header

Contains token type (JWT) and signing algorithm (HS256, RS256, etc.). Base64URL encoded.

Payload

Contains claims (user data, expiration, issuer, etc.). Base64URL encoded. Not encrypted - anyone can read this.

Signature

Verifies token hasn\'t been tampered with. Created by signing header+payload with secret or private key.

JWT Best Practices

  • Keep tokens short-lived: Use 15-60 minute expiration times
  • Use refresh tokens: Issue new access tokens without re-authentication
  • Never store secrets in JWTs: Payload is visible to anyone
  • Always verify signatures: Check token hasn\'t been tampered with
  • Validate all claims: Check exp, iss, aud, nbf before trusting token
  • Use HTTPS only: Prevent token interception

Frequently Asked Questions

Common questions about the JWT Decoder

A JWT is a compact, URL-safe token format used for securely transmitting information between parties. It consists of three parts: header (algorithm and token type), payload (claims/data), and signature (for verification). JWTs are commonly used for authentication and information exchange.

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ℹī¸ Disclaimer

This tool is provided for informational and educational purposes only. All processing happens entirely in your browser - no data is sent to or stored on our servers. While we strive for accuracy, we make no warranties about the completeness or reliability of results. Use at your own discretion.