JSON Web Tokens (JWT)

What are JSON Web Tokens (JWT)?

A JSON Web Token (JWT) is a widely used open standard designed for securely exchanging information between two parties—typically a client and a server.

Each JWT contains encoded JSON objects that include a set of claims.

These claims represent various types of data, such as user identity, permissions, or other essential details.

Structure of a JWT

A JWT is divided into three key components:

• **Header: **Provides details about the type of token and the algorithm used for signing.
• Payload: Contains the claims, which include the data to be shared.
• Signature: Ensures the token's authenticity and guards against tampering.

Common Use Cases

1. Authentication: JWTs are frequently used for user authentication. After a successful login, the server generates a JWT, which is included in subsequent client requests.
2. Authorization: JWTs can store user roles and permissions, granting access to specific resources.
3. Single Sign-On (SSO): JWTs streamline authentication across multiple systems or applications without requiring repeated logins.

Best Practices for Using JWTs

Set an expiration time to limit the token’s lifespan.

• Always use HTTPS when transmitting JWTs to prevent interception.
• Avoid embedding sensitive data in the JWT payload, as it is visible to anyone with access to the token.

🔗 Connect with me on LinkedIn:

Let’s dive deeper into the world of software engineering together! I regularly share insights on JavaScript, TypeScript, Node.js, React, Next.js, data structures, algorithms, web development, and much more. Whether you're looking to enhance your skills or collaborate on exciting topics, I’d love to connect and grow with you.

Follow me: Nozibul Islam

Comments

[Jason Purdy]

Can you provide some more information here? Maybe an example of what a JWT looks like? And what a payload looks like. I'm puzzled by what you mean by sensitive data in the payload.

Thanks!

[Aaron Moss]

A payload can be any set of data that stores information about the user, for example: {
"sub": "1234567890",
"name": "John Doe",
"admin": true
}, a helpful note I found online about the JWT payload though is for signed tokens, you should never store and sensitive information in the payload OR header elements as they are readable by anyone.

I suppose by sensitive data, they meant user personal info?

[Jay Pancholi]

Here you go

spellbook.muggleborn.dev

[Nozibul Islam]

thanks.

[Nozibul Islam]

Thanks for your comment! Apologies, but I’m unable to share more information at the moment. I’ll get back to you as soon as I can.

[Dhaval Gojiya]

How is a JWT token safe? Anyone can decrypt it and can see the payload dictionary data. There is an online tool available to decrypt tokens, and it shows the payload. 

[Thomas Broyer]

For anyone wanting to go a bit deeper on JWT: dev.to/tbroyer/what-are-jwt-nm0

TL;DR: you probably don't need them.