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JSON Web Token

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What is JWT?

JSON Web Token (JWT) is an open standard (RFC 7519) used for secure and compact data exchange as a JSON token. It is widely used for authentication and authorization in stateless APIs.

JWT Structure

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

HEADER.PAYLOAD.SIGNATURE

  • Header: token type & algorithm
  • Payload: claims (data)
  • Signature: integrity verification

How It Works (Short Flow)

  1. User logs in
  2. Server generates JWT
  3. Token is sent to client
  4. Client sends token with each request
  5. Server verifies the token

Sample Payload

ex.json
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Advantages

  • Stateless
  • High performance
  • Ideal for APIs & microservices

Drawbacks

  • Hard to revoke
  • Payload is readable
  • Risky if token leaks

Best Practices

  • Always use HTTPS
  • Short expiration time
  • Implement refresh tokens
  • Never store sensitive data
JWT is not just about tokens, but about trust and access boundaries.