Hello welcome! Today we'll be looking at JWT authentication, what it is? why it is used for and everything we need to know.

Authentication is a crucial part of any web application, ensuring that users can securely access their accounts and data. One of the most popular authentication methods today is JSON Web Tokens (JWT). We'll dive deep into JWT authentication in Node.js, explaining how it works, its benefits, and how you can implement it in your application.

What is JWT?

JWT (JSON Web Token) is a compact and self-contained way of securely transmitting information between parties as a JSON object. It is often used for authentication and authorization in web applications.

A JWT consists of three parts:

1. Header – Contains metadata about the token, including the signing algorithm.

2. Payload – Contains user information and other claims.

3. Signature – A cryptographic signature that ensures the token hasn’t been tampered with.

A sample JWT looks like this:

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOiIxMjM0NTY3ODkwIiwiaWF0IjoxNjUxMjM0NTY3LCJleHAiOjE2NTEyMzgxNjd9.LhYKKO8YqTAS67Y9qSOKGOUr4IU1DJYq5S5U1AMOQyU

Notice the three parts separated by dots.

• "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9" contains Header information.

• "eyJ1c2VySWQiOiIxMjM0NTY3ODkwIiwiaWF0IjoxNjUxMjM0NTY3LCJleHAiOjE2NTEyMzgxNjd9" contains the payload,

• "LhYKKO8YqTAS67Y9qSOKGOUr4IU1DJYq5S5U1AMOQyU" contains the signature.

You can check header and payload of your token in https://jwt.io . It will look something the in picture below.