SvelteKit JWT Authentication with Middleware: A Complete Implementation

Introduction

While there are many approaches to handling authentication, using JSON Web Tokens (JWT) without storing session data in a database provides a scalable and efficient solution that's perfect for distributed systems.

In this tutorial, I'll show you how to build a complete authentication system using SvelteKit (with TypeScript) that implements "pure JWT" authentication.

By "pure JWT," I mean we won't be querying the database to validate tokens on each request - instead, we'll rely on cryptographic verification of the JWT itself.

We'll still use a database to

• store user information and
• log JWT issuance for audit purposes

But the actual authentication will happen without database lookups, making our system more scalable and performant.

Sequence Diagram

This diagram is important, but you don't have to understand everything in the beginning.

If you only care about implementation & making it work quickly, you can skip this section.

Feel free to come back to this as and when you need to enhance your understanding.

Here's how our authentication flow works:

Now, let's dive in

• Part 1: Setup & JWT Basics
• Part 2: Authentication Flows
• Part 3: Protecting Routes & Security