Getting started in Sveltekit

Installation

Install Lucia using your package manager of your choice.

npm install -D lucia

Initialize Lucia

Import Lucia and initialize it with your adapter. Refer to the Database page to learn how to set up your database and initialize the adapter. Make sure to configure the sessionCookie option and register your Lucia instance type

// src/lib/server/auth.ts
import { Lucia } from "lucia";
import { dev } from "$app/environment";

const adapter = new BetterSQLite3Adapter(db); // your adapter

export const lucia = new Lucia(adapter, {
	sessionCookie: {
		attributes: {
			// set to `true` when using HTTPS
			secure: !dev
		}
	}
});

declare module "lucia" {
	interface Register {
		Lucia: typeof lucia;
	}
}

Setup hooks

We recommend setting up a handle hook to validate requests. The validated user will be available as local.user.

If you're curious about what's happening here, see the Validating requests page.

// src/hooks.server.ts
import { lucia } from "$lib/server/auth";
import type { Handle } from "@sveltejs/kit";

export const handle: Handle = async ({ event, resolve }) => {
	const sessionId = event.cookies.get(lucia.sessionCookieName);
	if (!sessionId) {
		event.locals.user = null;
		event.locals.session = null;
		return resolve(event);
	}

	const { session, user } = await lucia.validateSession(sessionId);
	if (session && session.fresh) {
		const sessionCookie = lucia.createSessionCookie(session.id);
		// sveltekit types deviates from the de-facto standard
		// you can use 'as any' too
		event.cookies.set(sessionCookie.name, sessionCookie.value, {
			path: ".",
			...sessionCookie.attributes
		});
	}
	if (!session) {
		const sessionCookie = lucia.createBlankSessionCookie();
		event.cookies.set(sessionCookie.name, sessionCookie.value, {
			path: ".",
			...sessionCookie.attributes
		});
	}
	event.locals.user = user;
	event.locals.session = session;
	return resolve(event);
};

Make sure to type App.Locals as well.

// src/app.d.ts
declare global {
	namespace App {
		interface Locals {
			user: import("lucia").User | null;
			session: import("lucia").Session | null;
		}
	}
}

export {};

Next steps

You can learn all the concepts and APIs by reading the Basics section in the docs. If you prefer writing code immediately, check out the Tutorials page or the examples repository.

This documentation often references the Copenhagen Book. This is an open-source guide on implementing auth and should come in handy when implementing anything auth, including passkeys, multi-factor authentication, and a bit of cryptography. We recommend reading it to learn more about auth in web applications.

If you have any questions, join our Discord server!