Getting started in Astro

Installation

Install Lucia using your package manager of your choice.

npm install 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/auth.ts
import { Lucia } from "lucia";

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

export const lucia = new Lucia(adapter, {
	sessionCookie: {
		attributes: {
			// set to `true` when using HTTPS
			secure: import.meta.env.PROD
		}
	}
});

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

Set up middleware

We recommend setting up a middleware to validate requests. The validated user will be available as local.user. You can just copy-paste the code into src/middleware.ts.

It's a bit verbose, but it just reads the session cookie, validates it, and sets a new cookie if necessary. Since Astro doesn't implement CSRF protection out of the box, it must be implemented. If you're curious about what's happening here, see the Validating requests page.

// src/middleware.ts
import { lucia } from "./auth";
import { verifyRequestOrigin } from "lucia";
import { defineMiddleware } from "astro:middleware";

export const onRequest = defineMiddleware(async (context, next) => {
	if (context.request.method !== "GET") {
		const originHeader = context.request.headers.get("Origin");
		const hostHeader = context.request.headers.get("Host");
		if (!originHeader || !hostHeader || !verifyRequestOrigin(originHeader, [hostHeader])) {
			return new Response(null, {
				status: 403
			});
		}
	}

	const sessionId = context.cookies.get(lucia.sessionCookieName)?.value ?? null;
	if (!sessionId) {
		context.locals.user = null;
		context.locals.session = null;
		return next();
	}

	const { session, user } = await lucia.validateSession(sessionId);
	if (session && session.fresh) {
		const sessionCookie = lucia.createSessionCookie(session.id);
		context.cookies.set(sessionCookie.name, sessionCookie.value, sessionCookie.attributes);
	}
	if (!session) {
		const sessionCookie = lucia.createBlankSessionCookie();
		context.cookies.set(sessionCookie.name, sessionCookie.value, sessionCookie.attributes);
	}
	context.locals.session = session;
	context.locals.user = user;
	return next();
});

Make sure to type App.Locals as well.

// src/env.d.ts

/// <reference types="astro/client" />
declare namespace App {
	interface Locals {
		session: import("lucia").Session | null;
		user: import("lucia").User | null;
	}
}

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!