The What, the How, and the Why of JWTs

Security isn’t just a priority, it's one of the most important parts of web development today. Whether you’re building a SaaS platform, a collaborative editor, or even a cloud-based document management system, securely managing user authentication and access to resources is a fundamental challenge. That’s where JSON Web Tokens (JWTs) come in, providing a stateless, scalable way to handle authentication.
For example, TinyMCE’s Import from Word feature requires setting up JWT authentication to make sure that only authorized users can upload and manage Word documents. Without JWTs, it’s nearly impossible to enforce proper security in multi-user environments where sensitive documents might be handled. JWTs enable TinyMCE to offer a high quality user experience while maintaining strict security controls over file uploads.
JWTs aren’t just important for Rich Text Editors or web components; they’re widely used across web apps for their simplicity, flexibility, and stateless design. In this blog, we’ll walk through what JWTs are, how they work, and why they’re crucial for building secure, scalable auth systems.

What are JWTs?

JSON Web Token or JWT is a token that allows secure data transmission between web servers. It’s a lightweight, self-contained solution that helps manage authentication and authorization without the need for server-side session storage. It’s more secure than traditional session based user authorization, but how?

Traditional User Based Session vs JWT Session

In the traditional approach, when a user logs in, the server stores their information in a session and sends a session ID to the client as a cookie. That app then includes this cookie in all future requests which allows the server to identify and authorize the user. Each time the server receives a request, it has to retrieve and validate the session ID before responding.

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In the JWT approach, when the client requests access, the server generates a JWT containing user information and sends it back to the client. The server doesn’t need to store any user data—everything is stored in the token on the client side. For each future request, the client includes the JWT instead of the user information, and the server verifies the token’s signature to confirm the user’s identity before responding.

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What Makes a JWT Work?

At first glance, a JWT might look like a random mess of characters, but under the hood, it’s a well-structured token designed for secure data exchange.

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

Let’s take a look at it this token the JWT debugger:

So here we see that the token is made up of 3 parts. The header, the Payload and the Signature:

Header – Contains metadata about the token, like the signing algorithm used.
Payload – This is where the actual data (e.g., user information) is stored.
Signature – This ensures the token hasn’t been tampered with.

Think of a JWT like a digital passport. The payload holds user-specific data, while the signature acts as a tamper-proof seal.

Why JWTs Matter for Stateless Authentication

Stateless authentication is crucial today. With JWTs, the server doesn’t need to maintain session data. Everything it needs to know is in the token. This makes JWTs perfect for scaling, especially when you’re dealing with microservices, serverless functions, or distributed systems where maintaining centralized session storage would be a nightmare. Remember, while JWTs are great for auth and data integrity, they’re not designed for data confidentiality. So if you need to transmit sensitive info, you’ll still need SSL/TLS and possibly encryption at the application level.

Common Pitfalls:

Token bloat – Keep the payload minimal. Don’t throw everything in just because you can.
Long-lived tokens – Short-lived tokens reduce the risk of exposure. For long-term sessions, consider using refresh tokens.
Insecure secret keys – Your secret key isn’t just a "key"; it’s the backbone of your token’s security. Use a long, complex, random string—no shortcuts.

JWTs are not just popular, they are also a practical solution for modern authentication challenges. Their stateless nature makes them ideal for scalable architectures, and when implemented correctly, they offer a clean, efficient way to manage user sessions without the need for server-side storage. But like any tool, they come with caveats. JWTs ensure data integrity, not confidentiality, so it’s on you to use them responsibly. Keep the payload light, avoid sensitive data, and always, always use a strong secret key.

At the end of the day, JWTs let you build faster, more scalable apps while keeping things secure. In a world where speed and security are everything, that’s a win-win.