Next.js Authentication: Code Examples and Libraries to Get You Started


React frameworks have come a long way in recent years. Next.js is another variation that is helping SaaS companies create apps and services at a faster pace. But what about the user management and authentication side of things? This mini-guide will shed some light on these key aspects.

What Is Next.js Authentication? 

Next.js is a JavaScript framework that’s used for building server-side rendered, static, and dynamic web applications with React. It provides a minimal setup for developers to get started and features a fast development cycle with automatic code splitting, optimized builds, and easy client-side and server-side rendering.
Authentication helps ensure that only authorized users can access a website or application and its data. It helps to protect sensitive information and prevents unauthorized access. This is commonly achieved through methods such as login and password authentication, OAuth, or JWT tokens. In Next.js, authentication can be implemented using various strategies, including server-side rendering, client-side only, or a combination of both.

In this article:

Next.js Rendering Patterns 

There are three ways that Next.js can render pages. These rendering patterns are:

  • Client-Side Rendering (CSR): The browser executes JavaScript to render the content dynamically on the client side. This means that the user’s browser will download and run JavaScript code that will generate the content for the user to view. This can lead to a faster initial loading experience, as the amount of data sent from the server to the client is minimized. However, the overall performance can be impacted if the JavaScript code is complex or if the user has a slow internet connection, as the rendering will be slower.
  • Server-Side Rendering (SSR): The server generates and sends an HTML page to the client, which is then displayed directly in the browser. This approach can lead to slower initial loading times, as the server has to generate the entire HTML page and send it to the client. However, the user can see the content immediately, even if they have a slow internet connection, as the page has already been pre-rendered by the server.

Static Site Generation (SSG): The HTML pages are pre-rendered at build time, which results in faster loading times and improved SEO, as the content is already available to search engines. This approach is best for sites that don’t have frequently changing content or that don’t require user interaction, such as blogs or portfolios.

Next.js Authentication Examples 

Static Page Authentication

This type of authentication applies to statically generated pages. They don’t have any data requirements that would block the page from rendering, such as getServerSideProps or getInitialProps. A static page renders the loading state and fetches the user from the client-side.

This pattern allows Next.js to serve preloaded pages from the central CDN – i.e., implementing authentication on pages that are pre-rendered at build time. This results in faster interactions.

Here is an example script for a profile page in Next.js using static page authentication:
Note: The next-auth/client package has been deprecated. In this example, we’ll use the next-auth/react package.

Install it by running this command:

npm install next-auth

Modify the _app.tsx file located in <next_js_project_folder>/pages/_app.tsx to include the SessionProvider library from the next-auth/react package:

import type { AppProps } from 'next/app'
import { SessionProvider } from "next-auth/react"

export default function App({
Component, pageProps: { session, ...pageProps }, }) {

  return (
        <SessionProvider session={session}>
        <Component {...pageProps} />

Add following code to <next_js_project_folder>/pages/index.tsx:

import { useSession  } from 'next-auth/react'

//const inter = Inter({ subsets: ['latin'] })

export default function Home() {
  const { data: session } = useSession()

if (session) {
         return <p>Authenticated</p>


return <p>Not Authenticated</p>

When you try to access the application via a web browser, the output should look like this:

Dynamic Page Authentication

This pattern applies to pages that are generated dynamically based on the URL. In other words, it’s the process of securing pages that are not statically defined in the code, but rather generated dynamically based on the URL. This prevents the exposure of unauthorized content before Next.js redirects the page.

Here’s an example of dynamic authentication for a profile page in Next.js using the getServerSideProps method:

import { useRouter } from 'next/router';
import axios from 'axios';

const ProfilePage = ({ user }) => {
  const router = useRouter();
  const { userId } = router.query;

  if (!user) {
    return <div>Not authorized</div>;

  return (
      <h1>Welcome, {}</h1>
      <p>Your email is {}</p>

export async function getServerSideProps({ req, res, query }) {
  const { userId } = query;

  try {
    const { data } = await axios.get(`$(userId)`);

    if (! {
      res.statusCode = 404;
      return { props: { user: null } };
    const { data: currentUser } = await axios.get('', {

    if (!== {
      res.statusCode = 403;
      return { props: { user: null } };

    return { props: { user:} };
  } catch (error) {
    res.statusCode = 500;
    return { props: { user: null } };

export default ProfilePage;

The output should look like this:

Note: The above code uses a free testing API, The API has the following data structure:

    "data": {
        "id": 2,
        "email": "[email protected]",
        "first_name": "Janet",
        "last_name": "Weaver",
        "avatar": ""
    "support": {
        "url": "",
        "text": "To keep ReqRes free, contributions towards server costs are appreciated!"

Open Source Next.js Authentication Libraries 


Auth.js is a JavaScript library or module that provides authentication and authorization functionality. It is used to handle the process of logging in, logging out, and managing user authentication and authorization within a Web and SaaS application.

Auth.js typically integrates with a backend service to manage user data, such as storing and retrieving user credentials and session information. It can also be used to implement various authentication strategies, such as email/password authentication, social media authentication, and token-based authentication.

Auth.js is commonly used in single-page applications (SPAs) and progressive web applications (PWAs) to manage the user authentication and authorization process.


NextAuth.js is an authentication and authorization library for Next.js. NextAuth.js provides a simple and flexible way to implement authentication and authorization functionality within Next.js applications.

NextAuth.js integrates with various identity providers, such as Google, Facebook, and Twitter, to allow users to log in using their existing accounts. It also supports email/password authentication, session management, and token-based authentication.

NextAuth.js handles the entire authentication and authorization process, including user sign-up, sign-in, and sign-out. It provides a secure and scalable solution for managing user authentication and authorization in Next.js applications.


Passport.js is a popular authentication middleware for Node.js that provides a simple and flexible way to add authentication to web applications. Passport.js supports a wide range of authentication strategies, including local authentication (using email/password), OAuth-based authentication (using social media platforms like Facebook, Twitter, and Google), and token-based authentication (using JSON Web Tokens, JWT).

Passport.js can be used in Next.js applications to implement authentication and authorization. To do this, Passport.js is integrated into the Next.js server-side runtime, where it can handle authentication requests and manage user sessions.

To use Passport.js in a Next.js application, you would typically create a middleware function that initializes Passport.js and sets up the desired authentication strategies. This middleware function would be included in the Next.js server-side runtime, so that it can be executed for every incoming request.

Iron Session 

Iron Session is a session middleware for the Iron framework, which is a high-level web framework for the Rust programming language. It allows you to store session data on the server, which can be used to persist information across multiple requests from the same client.

In a web application, a session is a mechanism for storing data on the server that is associated with a specific client. This data can be used to track the client’s activity and maintain state between requests. The Iron Session middleware provides a simple and secure way to manage sessions in a Rust web application.

With Iron Session, you can store data such as the user’s session ID, login status, and other information, and retrieve this data on subsequent requests to the server. This allows you to build web applications that can maintain state and provide a seamless experience for the user.

Authentication and Authorization with Frontegg

The industry standard today is to use Authentication providers to “build the door”, but what about Authorization (the door knob)? Most authentication vendors don’t go that extra mile, forcing SaaS vendors to invest in expensive in-house development or look for third-party fixes that introduce more technical challenges. This often delays investment in core technology development, which negatively impacts innovation and time-to-market (TTM) metrics. 

Frontegg’s end-to-end user management platform allows you to authenticate and authorize users with just a few clicks. Integration takes just a few minutes and lines of code, thanks to its plug-and-play nature. It’s also multi-tenant by design.