🔐 JWT (JSON Web Token) in a Nutshell! 🌐

Chandradeep Kumar
4 min readAug 1, 2023

Introduction to JWT

In the realm of modern web applications, secure and reliable user authentication is paramount. JWT, or JSON Web Token, has emerged as a popular solution for this purpose. JWT is a compact, secure token format widely used for authentication and data exchange in web applications. JWTs are a powerful tool that can be used to secure and simplify communication between systems.

What is JWT?

It is digitally signed token authentication method, as the name suggests, represented in JSON format. JWTs are designed in such a way that if correct Bearer token is provided in the header then only one can access the data stored in the apis . It is the secured way communcating between two clients.

Structure of JWT :-

A JWT token consists of maily three parts: the header, the payload, and the signature. Each part have its own distinct pupose . Lets get deep into this :

  1. Header: This part of token generally contains the hashing algorithm of the token and type of token that has been passed into it.For example, the header could be {"alg": "HS256", "typ": "JWT"}.
  2. Payload: This part basically contains the data that is being transmitted. It is typically used to represent user’s identity such as username or password.
  3. Signature: This part is used to verify the authenticity of the token. It is calculated using the header, the payload, and a secret key. The signature is created by encoding the base64Url-encoded header and payload along with a secret key using the specified algorithm.

🌐 Example:

Let’s go through this example , where you have logged into an online platform or you want to fetch data from the database through api calling .The server generates a new JWT token that looks like this:

  • Header: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9
  • Payload: eyJ1c2VyX2lkIjoiMTIzNDUiLCJyb2xlIjoiYWRtaW4iLCJleHAiOjE2Nzk5MzI0MTJ9
  • Signature: uDuhKdu03OLvLju42EfPDP0bK9-P8s14sj1jXjTzE_w

This token basically contains your user ID, role (admin in this case), and an expiration time ,after that expiration time you’ll need to regenerate the token to access the data.

Structure of JWT

How JWT Works

JWT’s working principle revolves around the exchange of tokens between a server and a client. Here’s a step-by-step breakdown:

  1. User Authentication: When a user logs in, the server authenticates their credentials and generates a fresh random JWT token.
  2. Token Transmission: The JWT token is securely transmitted to the client.
  3. Token Usage: For subsequent requests, the client includes the JWT token in the Authorization header.
  4. Server Verification: The server then verifies the token’s integrity, authenticity, and expiration. If all checks pass, the request is processed.

Advantages of JWT

JWT comes with a range of benefits, making it a popular choice for modern applications:

  1. Enhanced Security: JWTs are digitally signed, ensuring that the data hasn’t been tampered with. You can trust the information stored in the token.
  2. Compact & Efficient: Being lightweight, JWTs can be easily transmitted as URL parameters or within an HTTP header.
  3. Single Sign-On (SSO): JWTs can be used to implement SSO solutions, allowing users to log in to multiple systems with a single set of credentials.
  4. Reduced Server Load: Stateless nature means servers don’t need to store session data, reducing the load and improving performance.
  5. Extensibility: You can include custom claims in the payload, allowing you to tailor JWTs to your specific needs.

Security Considerations

While JWT is a powerful tool, it’s essential to be mindful of security considerations:

  1. Token Expiration: Always set a reasonable expiration time to limit the window of vulnerability.
  2. Secure Transmission: Use HTTPS to protect the token during transmission.
  3. Avoid Sensitive Information: Never include sensitive data in the payload; use the token for identification, not for confidential data storage.

Real-World Applications

JWT finds diverse applications, including:

  1. User Authentication: JWTs serve as a robust authentication mechanism for web and mobile applications.
  2. Authorization: By incorporating user roles and permissions in the payload, JWTs can manage access control.
  3. Single Sign-On (SSO): JWTs enable seamless authentication across multiple applications.
  4. Secure Communication: JWTs can be used to secure API communication between microservices.


JWT is a versatile and efficient method for securing user authentication in web applications. Understanding its inner workings and best practices can significantly contribute to building safer, more scalable, and performant systems.

For a more in-depth exploration of JWT and its applications, don’t forget to read the full article: [Insert Medium Article Link]

Unlock the power of JWT and elevate your web application’s security today! 🗝️💪