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JWT Decoder

Decode and analyze JWT (JSON Web Token). Check header, payload, signature and verify expiration time.

About JWT

JWT (JSON Web Token) is a compact, URL-safe means of representing claims to be transferred between two parties. It consists of three parts: Header, Payload, and Signature.

Common Payload Claims

  • sub - Subject (user ID)
  • iat - Issued at (timestamp)
  • exp - Expiration time (timestamp)
  • iss - Issuer
  • aud - Audience
  • nbf - Not before (timestamp)

Key Features​

🔓 JWT Decoding​

  • Automatic separation of header, payload, signature
  • Base64 URL decoding
  • JSON formatting

⏰ Timestamp Analysis​

  • Check iat (issued at)
  • Check exp (expiration) and display expiration status
  • Check nbf (not before)

📋 Copy Function​

  • Copy header JSON
  • Copy payload JSON
  • Copy signature

What is JWT?​

JWT (JSON Web Token) is a compact and URL-safe way to securely transfer information between two parties.

JWT Structure​

JWT consists of three parts separated by dots (.):

header.payload.signature
  1. Header: Token type and algorithm information
  2. Payload: Claim data
  3. Signature: Value signed with secret key from header and payload

Common Claims​

Standard Claims​

  • sub (Subject): Token subject (user ID)
  • iss (Issuer): Token issuer
  • aud (Audience): Token audience
  • exp (Expiration): Expiration time
  • iat (Issued At): Issue time
  • nbf (Not Before): Valid start time

Custom Claims​

You can freely add necessary information to JWT payload:

  • User name, email
  • Permissions, roles
  • Other metadata

Security Notes​

⚠️ Important: This tool runs client-side and does not perform signature verification.

  • JWT signature verification must be done server-side with secret key
  • Do not store sensitive information in payload (Base64 is not encryption)
  • Use HTTPS to transmit JWT

Use Cases​

1. Authentication​

Issue JWT after user login, include in subsequent requests

2. Information Exchange​

Secure information transfer between two systems

3. API Authorization​

Token for verifying API access permissions

4. SSO (Single Sign-On)​

Share authentication across multiple services

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Feel free to send us your feedback or suggestions anytime!

Privacy​

This tool operates entirely on the client side. Your JWT data is never sent to a server and is processed only in your browser.