JWT Encoder/Decoder

What is JWT Encoder/Decoder?

JWT Encoder/Decoder is an online tool that allows you to encode and decode JSON Web Tokens (JWT). A JWT is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure.

JWTs are commonly used for authentication and information exchange in web applications. They consist of three parts separated by dots (.): Header, Payload, and Signature. This tool helps you understand the structure of JWTs by encoding your custom header and payload, or decoding existing tokens to view their contents.

JWT Structure

A JWT consists of three parts:

• Header: Contains metadata about the token, typically the type of token (JWT) and the signing algorithm being used (e.g., HMAC SHA256 or RSA)
• Payload: Contains the claims or statements about an entity (typically the user) and additional data. Claims can be registered, public, or private
• Signature: Used to verify that the sender of the JWT is who it says it is and to ensure that the message wasn't changed along the way

Common Use Cases

• Authentication: Once a user logs in, each subsequent request includes the JWT, allowing access to routes, services, and resources
• Information Exchange: JWTs are a secure way of transmitting information between parties because they can be signed
• API Authorization: Stateless authentication for RESTful APIs
• Single Sign-On (SSO): Share authentication across multiple applications
• Token-based Authentication: Replace session-based authentication with stateless tokens

How to Use JWT Encoder

1. Edit Header: Modify the JSON header to specify the algorithm and token type
2. Edit Payload: Add your claims and data to the payload JSON object
3. Enter Secret: Provide a secret key for signing (for demonstration purposes)
4. Click Encode: Generate your JWT token
5. Copy Token: Use the copy button to copy the encoded JWT

How to Use JWT Decoder

1. Paste JWT: Paste your JWT token into the input field
2. Click Decode: The tool will parse and display the header, payload, and signature
3. View Components: Examine the decoded header and payload in formatted JSON
4. Verify Signature: View the signature component of the token

Security Considerations

Important: This is a demonstration tool. In production environments:

• Never expose your secret keys in client-side code
• Always validate JWTs on the server side
• Use strong, randomly generated secrets
• Implement proper token expiration and refresh mechanisms
• Use HTTPS to prevent token interception
• Store tokens securely (avoid localStorage for sensitive data)

Example JWT

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

This token decodes to:

Header:

{
  "alg": "HS256",
  "typ": "JWT"
}

Payload:

{
  "sub": "1234567890",
  "name": "John Doe",
  "iat": 1516239022
}