Sign in with username and password in Next.js Pages Router

Before starting, make sure you’ve setup Lucia and your database.

This guide will cover how to implement a simple username and password authentication using Lucia in Next.js Pages Router. It will have 3 parts:

A sign up page
A sign in page
A profile page with a logout button

Clone project#

You can get started immediately by cloning the Next.js example from the repository.

npx degit lucia-auth/examples/nextjs-pages/username-and-password <directory_name>

Alternatively, you can open it in StackBlitz.

Update your database#

Add a username column to your table. It should be a string (TEXT, VARCHAR etc) type that’s unique.

Make sure you update Lucia.DatabaseUserAttributes whenever you add any new columns to the user table.

// app.d.ts

/// <reference types="lucia" />
declare namespace Lucia {
	type Auth = import("./lucia.js").Auth;
	type DatabaseUserAttributes = {
		username: string;
	};
	type DatabaseSessionAttributes = {};
}

Configure Lucia#

We’ll expose the user’s username to the User object by defining getUserAttributes.

// auth/lucia.ts
import { lucia } from "lucia";
import { nextjs_future } from "lucia/middleware";

export const auth = lucia({
	adapter: ADAPTER,
	env: process.env.NODE_ENV === "development" ? "DEV" : "PROD",
	middleware: nextjs_future(),

	getUserAttributes: (data) => {
		return {
			username: data.username
		};
	}
});

export type Auth = typeof auth;

Create pages/signup.tsx and add a form with inputs for username and password. The form should make a POST request to /api/signup.

// pages/signup.tsx
import { useRouter } from "next/router";

import Link from "next/link";

const Page = () => {
	const router = useRouter();
	return (
		<>
			<h1>Sign up</h1>
			<form
				method="post"
				action="/api/signup"
				onSubmit={async (e) => {
					e.preventDefault();
					const formData = new FormData(e.currentTarget);
					const response = await fetch(e.currentTarget.action, {
						method: "POST",
						body: JSON.stringify({
							username: formData.get("username"),
							password: formData.get("password")
						}),
						headers: {
							"Content-Type": "application/json"
						},
						redirect: "manual"
					});
					if (response.status === 0 || response.ok) {
						router.push("/"); // redirect to profile page on success
					}
				}}
			>
				<label htmlFor="username">Username</label>
				<input name="username" id="username" />
				<br />
				<label htmlFor="password">Password</label>
				<input type="password" name="password" id="password" />
				<br />
				<input type="submit" />
			</form>
			<Link href="/login">Sign in</Link>
		</>
	);
};

export default Page;

Create users#

Create pages/api/signup.ts and handle POST requests.

Users can be created with Auth.createUser(). This will create a new user, and if key is defined, a new key. The key here defines the connection between the user and the provided unique username (providerUserId) when using the username & password authentication method (providerId). We’ll also store the password in the key. This key will be used get the user and validate the password when logging them in. The type for attributes property is Lucia.DatabaseUserAttributes, which we added username to previously.

After successfully creating a user, we’ll create a new session with Auth.createSession() and store it as a cookie with AuthRequest.setSession(). AuthRequest can be created by calling Auth.handleRequest() with IncomingMessage and OutgoingMessage.

// pages/api/signup.ts
import { auth } from "@/auth/lucia";

import type { NextApiRequest, NextApiResponse } from "next";

const handler = async (req: NextApiRequest, res: NextApiResponse) => {
	if (req.method !== "POST") return res.status(405);
	const { username, password } = req.body as {
		username: unknown;
		password: unknown;
	};
	// basic check
	if (
		typeof username !== "string" ||
		username.length < 4 ||
		username.length > 31
	) {
		return res.status(400).json({
			error: "Invalid username"
		});
	}
	if (
		typeof password !== "string" ||
		password.length < 6 ||
		password.length > 255
	) {
		return res.status(400).json({
			error: "Invalid password"
		});
	}
	try {
		const user = await auth.createUser({
			key: {
				providerId: "username", // auth method
				providerUserId: username.toLowerCase(), // unique id when using "username" auth method
				password // hashed by Lucia
			},
			attributes: {
				username
			}
		});
		const session = await auth.createSession({
			userId: user.userId,
			attributes: {}
		});
		const authRequest = auth.handleRequest({
			req,
			res
		});
		authRequest.setSession(session);
		return res.redirect(302, "/"); // profile page
	} catch (e) {
		// this part depends on the database you're using
		// check for unique constraint error in user table
		if (
			e instanceof SomeDatabaseError &&
			e.message === USER_TABLE_UNIQUE_CONSTRAINT_ERROR
		) {
			return res.status(400).json({
				error: "Username already taken"
			});
		}

		return res.status(500).json({
			error: "An unknown error occurred"
		});
	}
};

export default handler;

Case sensitivity#

Depending on your database, user123 and USER123 may be treated as different strings. To avoid 2 users having the same username with different cases, we are going to make the username lowercase before creating a key. This is crucial when setting a user-provided input as a provider user id of a key.

On the other hand, making the username stored as a user attribute lowercase is optional. However, if you need to query users using usernames (e.g. url /user/user123), it may be beneficial to require the username to be lowercase, store 2 usernames (lowercase and normal), or set the database to ignore casing when compare strings (e.g. using LOWER() in SQL).

const user = await auth.createUser({
	key: {
		providerId: "username", // auth method
		providerUserId: username.toLowerCase(), // unique id when using "username" auth method
		password // hashed by Lucia
	},
	attributes: {
		username
	}
});

Error handling#

Lucia throws 2 types of errors: LuciaError and database errors from the database driver or ORM you’re using. Most database related errors, such as connection failure, duplicate values, and foreign key constraint errors, are thrown as is. These need to be handled as if you were using just the driver/ORM.

if (
	e instanceof SomeDatabaseError &&
	e.message === USER_TABLE_UNIQUE_CONSTRAINT_ERROR
) {
	// username already taken
}

Redirect authenticated users#

Authenticated users should be redirected to the profile page whenever they try to access the sign up page. You can validate requests by creating by calling AuthRequest.validate(). This method returns a Session if the user is authenticated or null if not.

// pages/signup.tsx
import { useRouter } from "next/router";
import { auth } from "@/auth/lucia";

import Link from "next/link";

import type { GetServerSidePropsContext, GetServerSidePropsResult } from "next";

export const getServerSideProps = async (
	context: GetServerSidePropsContext
): Promise<GetServerSidePropsResult<{}>> => {
	const authRequest = auth.handleRequest(context);
	const session = await authRequest.validate();
	if (session) {
		return {
			redirect: {
				destination: "/",
				permanent: false
			}
		};
	}
	return {
		props: {}
	};
};

const Page = () => {
	// ...
};

export default Page;

Create pages/login.tsx and also add a form with inputs for username and password. The form should make a POST request to /api/login.

// pages/login.tsx
import { useRouter } from "next/router";

import Link from "next/link";

const Page = () => {
	const router = useRouter();
	return (
		<>
			<h1>Sign in</h1>
			<form
				method="post"
				action="/api/login"
				onSubmit={async (e) => {
					e.preventDefault();
					const formData = new FormData(e.currentTarget);
					const response = await fetch(e.currentTarget.action, {
						method: "POST",
						body: JSON.stringify({
							username: formData.get("username"),
							password: formData.get("password")
						}),
						headers: {
							"Content-Type": "application/json"
						},
						redirect: "manual"
					});

					if (response.status === 0 || response.ok) {
						router.push("/"); // redirect to profile page on success
					}
				}}
			>
				<label htmlFor="username">Username</label>
				<input name="username" id="username" />
				<br />
				<label htmlFor="password">Password</label>
				<input type="password" name="password" id="password" />
				<br />
				<input type="submit" />
			</form>
			<Link href="/signup">Create an account</Link>
		</>
	);
};

export default Page;

Authenticate users#

Create pages/api/login.ts and handle POST requests.

The key we created for the user allows us to get the user via their username, and validate their password. This can be done with Auth.useKey(). If the username and password is correct, we’ll create a new session just like we did before. If not, Lucia will throw an error. Make sure to make the username lowercase before calling useKey().

// pages/api/login.ts
import { auth } from "@/auth/lucia";
import { LuciaError } from "lucia";

import type { NextApiRequest, NextApiResponse } from "next";

const handler = async (req: NextApiRequest, res: NextApiResponse) => {
	if (req.method !== "POST") return res.status(405);
	const { username, password } = req.body as {
		username: unknown;
		password: unknown;
	};
	// basic check
	if (
		typeof username !== "string" ||
		username.length < 1 ||
		username.length > 31
	) {
		return res.status(400).json({
			error: "Invalid username"
		});
	}
	if (
		typeof password !== "string" ||
		password.length < 1 ||
		password.length > 255
	) {
		return res.status(400).json({
			error: "Invalid password"
		});
	}
	try {
		// find user by key
		// and validate password
		const key = await auth.useKey("username", username.toLowerCase(), password);
		const session = await auth.createSession({
			userId: key.userId,
			attributes: {}
		});
		const authRequest = auth.handleRequest({
			req,
			res
		});
		authRequest.setSession(session);
		return res.redirect(302, "/"); // profile page
	} catch (e) {
		if (
			e instanceof LuciaError &&
			(e.message === "AUTH_INVALID_KEY_ID" ||
				e.message === "AUTH_INVALID_PASSWORD")
		) {
			// user does not exist
			// or invalid password
			return res.status(400).json({
				error: "Incorrect username or password"
			});
		}
		return res.status(500).json({
			error: "An unknown error occurred"
		});
	}
};

export default handler;

Redirect authenticated users#

As we did in the sign up page, redirect authenticated users to the profile page.

// pages/login.tsx
import { auth } from "@/auth/lucia";

import Link from "next/link";

import type { GetServerSidePropsContext, GetServerSidePropsResult } from "next";

export const getServerSideProps = async (
	context: GetServerSidePropsContext
): Promise<GetServerSidePropsResult<{}>> => {
	const authRequest = auth.handleRequest(context);
	const session = await authRequest.validate();
	if (session) {
		return {
			redirect: {
				destination: "/",
				permanent: false
			}
		};
	}
	return {
		props: {}
	};
};

const Page = () => {
	// ...
};

export default Page;

Profile page#

Create pages/index.tsx. This page will show some basic user info and include a logout button.

Unauthenticated users should be redirected to the login page. The user object is available in Session.user, and you’ll see that User.username exists because we defined it in first step with getUserAttributes() configuration.

// pages/index.tsx
import { auth } from "@/auth/lucia";
import { useRouter } from "next/router";

import type {
	GetServerSidePropsContext,
	GetServerSidePropsResult,
	InferGetServerSidePropsType
} from "next";

export const getServerSideProps = async (
	context: GetServerSidePropsContext
): Promise<
	GetServerSidePropsResult<{
		userId: string;
		username: string;
	}>
> => {
	const authRequest = auth.handleRequest(context);
	const session = await authRequest.validate();
	if (!session) {
		return {
			redirect: {
				destination: "/login",
				permanent: false
			}
		};
	}
	return {
		props: {
			userId: session.user.userId,
			username: session.user.username
		}
	};
};

const Page = (
	props: InferGetServerSidePropsType<typeof getServerSideProps>
) => {
	const router = useRouter();
	return (
		<>
			<h1>Profile</h1>
			<p>User id: {props.userId}</p>
			<p>Username: {props.username}</p>
			<form
				method="post"
				action="/api/logout"
				onSubmit={async (e) => {
					e.preventDefault();
					const response = await fetch("/api/logout", {
						method: "POST",
						redirect: "manual"
					});
					if (response.status === 0 || response.ok) {
						router.push("/login"); // redirect to login page on success
					}
				}}
			>
				<input type="submit" value="Sign out" />
			</form>
		</>
	);
};

export default Page;

Sign out users#

Create pages/api/logout.ts and handle POST requests.

When logging out users, it’s critical that you invalidate the user’s session. This can be achieved with Auth.invalidateSession(). You can delete the session cookie by overriding the existing one with a blank cookie that expires immediately. This can be created by passing null to Auth.createSessionCookie().

// pages/api/logout.ts
import { auth } from "@/auth/lucia";

import type { NextApiRequest, NextApiResponse } from "next";

const handler = async (req: NextApiRequest, res: NextApiResponse) => {
	if (req.method !== "POST") return res.status(405);
	const authRequest = auth.handleRequest({ req, res });
	// check if user is authenticated
	const session = await authRequest.validate();
	if (!session) {
		return res.status(401).json({
			error: "Unauthorized"
		});
	}
	// make sure to invalidate the current session!
	await auth.invalidateSession(session.sessionId);
	// delete session cookie
	authRequest.setSession(null);
	return res.redirect(302, "/login");
};

export default handler;

Sign in with username and password in Next.js Pages Router

Clone project#

Update your database#

Configure Lucia#

Sign up page#

Create users#

Case sensitivity#

Error handling#

Redirect authenticated users#

Sign in page#

Authenticate users#

Redirect authenticated users#

Profile page#

Sign out users#