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What is Next JS? All You Need to Know About Next.js

Are you looking to use Next.js for your next web project and want to understand how the framework works? Or are wondering what is Next JS? It is a web framework built on top of the React framework.

It extends the capabilities of React by including some powerful features like routing, optimized rendering, data fetching, etc.

In this tutorial, we’ll explain all there is to know about Next.js. This guide will serve as a starting point to help you become a better frontend developer.

Overview of Next.js

Next.js is a powerful framework for building web applications. It extends React, a popular JavaScript library for building user interfaces, by introducing the ability to render components on the server side.

This essentially means faster load times and better SEO because search engines can crawl the content more efficiently.

Brief History and Development of Next.js

Developed by Vercel (formerly Zeit), Next.js was launched in 2016. It addressed key challenges faced by React developers, particularly around SEO and performance. Over the years it has evolved significantly.

With each update, it has added features like static site generation and API routes, making it a comprehensive solution for building modern web apps.

This constant evolution reflects a commitment to meeting the changing needs of web developers and the industry.

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Importance of Next.js in Modern Web Development

Next.js is crucial in modern web development for several reasons:

  1. SEO-Friendly: It improves the visibility of web applications on search engines, a key factor for online success.

  2. Performance Optimization: Next enhances the performance of web applications. Faster load times and efficient data handling contribute to a better user experience.

  3. Developer Experience:

    Vercel designed this framework with the developer in mind. It simplifies processes, supports fast development cycles, and integrates seamlessly with various tools and libraries.
  4. Flexible Data Fetching: It offers multiple ways to fetch data, such as static generation and server-side rendering. This flexibility allows developers to choose the most efficient method for their projects.

  5. Productivity: Features like hot reloading and built-in CSS support streamline the development process, making it more efficient and less error-prone.

Core Concepts of Next.js

Let’s delve into the core concepts of Next.js, which have made it such a powerhouse in the world of modern web development.

Server-side Rendering (SSR) vs. Client-side Rendering

Rendering is all about how we get our web pages to appear in the user’s browser. Next.js brings an interesting twist to this process.

server room

Server-Side Rendering (SSR)

In SSR, the web page’s content is generated on the server before being sent to the client. This means the HTML, CSS, and JavaScript are already processed and rendered into the final page layout when it reaches the user’s browser.

This approach is beneficial for SEO, as search engines can easily crawl and index the content. It also ensures a faster initial page load.

Client-Side Rendering (CSR)

With CSR, the web page renders in the user’s browser using JavaScript. The server sends a minimal HTML page with JavaScript code that renders the actual page content.

Once loaded in the browser, the JavaScript fetches additional data and updates the page dynamically. This approach allows for interactive, app-like user experiences. However, it usually has a slower initial load and may pose challenges for SEO.

Server-side rendering vs Client-side rendering

Server-side RenderingClient-Side-Rendering
DescriptionSSR means that the HTML of a webpage is generated on the server, before it is sent to the client’s browser.CSR is when the webpage is rendered in the browser using JavaScript.
ProsSEO Benefits: Search engines can easily crawl and index the content.Reduced Server Load
Faster Page Transitions
ConsHeavier Server Load
Full Page Reloads
Slower Initial Load
Not easy for search engines to crawl

Automatic Code Splitting for Faster Page Loads

The framework automatically splits your code into small chunks. Think of it like a puzzle, where each piece is a part of your application.

When users visit a page, they only download the pieces needed for that page, not the entire puzzle. This significantly reduces the load time, as smaller files are faster to download and process.

Built-in CSS and Sass Support

Styling in Next.js is a breeze. It offers out-of-the-box support for CSS and Sass. This allows you to write styles in a way you’re probably already familiar with.

You can import CSS and Sass files directly into your JavaScript components. This feature simplifies the process of styling your applications.

Key Features of Next.js

Next.js offers a range of features designed to enhance your web application’s performance and user experience. This section will focus more on exploring some of these features.

Enhanced Performance

Next.js is for high performance, making your web applications run more efficiently. Imagine a highway where every car moves smoothly without traffic jams. That’s what this framework does for your web app.

It uses techniques like server-side rendering and static generation to serve content faster. This means your website loads quickly, providing a better experience for your users.

Image Optimization

Handling images can be tricky in web development, as large images can slow down your site. Next.js offers a built-in Image component that automatically optimizes images for you.

This component adjusts the size of your images based on the user’s screen, ensuring they’re not unnecessarily large and heavy. It’s like having a tool that automatically resizes and compresses your photos to keep your site speedy.

Script Optimization

Next.js intelligently manages the loading of external scripts, such as those used for analytics or ads. This optimization ensures these scripts do not slow down your site’s loading speed.

It’s akin to a traffic control system that intelligently manages the flow of vehicles, ensuring smooth travel without delays.

Developer Experience

The framework is designed with the developer in mind. It provides a range of features that make web development more efficient and enjoyable. Below, we’ll explain some of them.

File-system Based Routing

Setting up routes is as easy as creating a file in your project. No need for complex configuration. Just create a file in the pages directory; voila, it automatically becomes a route.

For example, creating a file named about.js in the pages directory automatically routes to /about.

// pages/about.js

export default function About() {
    return <div>About us</div>;

Just by creating this about.js file, you’ve defined a route. It’s that simple!

API Routes to Build API Endpoints with Serverless Functions

Next.js allows you to create API endpoints as serverless functions. These are also file-based. You simply create a JavaScript file under the pages/api directory, and this file becomes an API route.

For instance, to create a simple API endpoint to return a “Hello, World!” message:

// pages/api/hello.js

export default function handler(req, res) {
    res.status(200).json({ message: 'Hello, World!' });

Accessing /api/hello in your application will now return a JSON response with the “Hello, World!” message. It’s like having a mini-backend within your frontend framework.

Built-in TypeScript Support

TypeScript has grown in popularity thanks to its ability to catch errors early and make JavaScript more maintainable. Next.js comes with built-in TypeScript support, meaning you can start using TypeScript right out of the box.

To start using TypeScript, you just need to add a tsconfig.json file in your project root (Next can create this for you automatically) and rename your .js files to .tsx (if they contain JSX) or .ts (if they don’t).

Here’s a simple example in TypeScript:

// pages/index.tsx

type Props = {
    title: string;

const Home: React.FC<Props> = ({ title }) => <div>{title}</div>;

export default Home;

With TypeScript, you get autocomplete and type checking, which enhances code quality and developer productivity.

Deployment and Scalability

Deployment and scalability are crucial in modern web development. They determine how easily your application can be put into production and how well it adapts to increasing loads or changing needs.

Vercel Platform Integration

Vercel, the company behind Next.js, provides a cloud platform for hosting websites and web services. This platform is finely tuned for Next applications.

Support for Environment Variables

Next.js supports environment variables, a critical feature for modern applications. Environment variables let you manage and vary your app’s configuration between different environments (like development, staging, and production) without changing your code.

  1. Security and Flexibility: You can store sensitive information like API keys in environment variables, keeping them secure and out of your codebase. It’s like having a safe for your valuable items.

  2. Easy Configuration: Setting up environment variables in Next.js is straightforward. You can create a .env.local file in your project root and add your variables there. Next.js will load these variables automatically.

Setting Up a Next.js Project

Setting up a Next.js project is straightforward, thanks to its zero-config philosophy. Once you install Next and have a basic understanding of its directory structure, you’re well on your way to building fast, scalable web applications. This section will explain the steps to help you start with Next.js.


To fully understand how this framework works, you’ll need to have the following in place:

  • NPM installed on your machine

  • Basic understanding of JavaScript and the React framework

Please check out the video below if you need a refresher on React.

Installing and Configuring Next.js

1. Installation

To start, you need Node.js installed on your system. Next.js requires Node.js 10.13 or later. Once you have Node.js ready, you can create a new Next.js project using the following command:

npx create-next-app@latest my-next-app

This command creates a new directory called my-next-app with all the necessary files and configurations for a Next.js project.

2. Configuration

Next.js is designed to work out of the box with little need for configuration. However, if you need to customize your setup, you can do so by adding a next.config.mjs file in the root of your project.

This file is where you can configure various aspects of Next.js, like customizing the build process, adding environment variables, and more.

Directory Structure and File Organization

After installation, you’ll notice that Next.js creates a specific set of directories and files in your project:

  • pages/: This is where your application’s pages live. Each JavaScript file under this directory becomes a route for your application.

  • public/: Static files like images, fonts, and other assets go here. You can access them directly via the browser.

  • styles/: This is where custom CSS stylesheet should be added.

This structure helps organize your code logically and makes it easier for other developers to understand and contribute to your project.

To start the development server, navigate to your project directory in the terminal and run:

npm run dev

This command starts the Next.js development server on http://localhost:3000 by default.

Accessing Your Application: Open a web browser and go to http://localhost:3000. You will see your Next.js application running. Any changes you make to the components or pages will be automatically updated and reflected here, thanks to the hot reloading feature.

Using a Different Port If you need to run the server on a different port, you can do so by modifying the dev script in your package.json:

"scripts": {
  "dev": "next -p 4000"

This example changes the port to 4000. After making this change, running npm run dev will start the server on http://localhost:4000.

To learn more about using Next, check out the video below.

Advanced Topics in Next.js

Now, you have a basic understanding of how Next.js works and the steps to create your first Next.js app. Let’s explore some advanced concepts to improve your knowledge of the framework.

Dynamic Routing

Dynamic routing in Next.js allows you to create pages with dynamic routes. You can have dynamically generated URLs based on data, like user IDs or blog post slugs.

Creating Dynamic Routes: To create a dynamic route, add square brackets to the page name, like [id].js. This tells Next that this is a dynamic page. Here is an example.

// pages/posts/[id].js

import { useRouter } from 'next/router';

const Post = () => {
  const router = useRouter();
  const { id } = router.query;

  return <div>Post ID: {id}</div>;

export default Post;

With this setup, a path like /posts/123 will render the Post component, with id being 123.

Fetching Data for Dynamic Routes: Inside your dynamic page, you use getStaticProps to fetch data at build time or getServerSideProps to fetch data at request time. This data then renders the page.

Example: Suppose you have a blog. You can have a file named [slug].js under pages/posts that will match any route like /posts/my-first-post.

Fetching Data and Managing State

Next.js supports various data fetching methods and state management patterns:

  1. Static Generation with getStaticProps: Fetches data at build time. Useful for pages that can be pre-rendered with data that doesn’t change often.

  2. Server-side Rendering with getServerSideProps: Fetches data on each request. Good for pages that need constantly updated data.

  3. Client-side Data Fetching: You can fetch data directly on the client side, perhaps using React hooks like useEffect.

  4. State Management: Next.js also works with state management libraries like Redux or Context API for managing application state.

Integrating with Headless CMS

A headless CMS provides a way to manage content without a front-end layer. You can integrate a headless CMS with Next to manage your content:

  1. Fetching Content: Use APIs provided by the headless CMS to fetch content in your Next.js pages using getStaticProps or getServerSideProps.

  2. Dynamic Content Generation: Use dynamic routing to create pages based on content fetched from the headless CMS.

  3. Example CMSs: Popular choices include Contentful, Sanity, Strapi, and more.

Next.js Best Practices

Here are some SEO and security tips to help you become a better Next.js developer.

SEO Optimization Techniques

  1. Server-Side Rendering (SSR): Next.js’ SSR feature is a boon for SEO. It ensures that your content is fully rendered when search engines crawl your site, improving visibility and indexation.

  2. Dynamic Meta Tags: Use Next.js’s Head component to dynamically set meta tags for each page. This is crucial for providing unique, relevant meta information to search engines.

    import Head from 'next/head';
    const MyPage = () => (
          <title>My Page Title</title>
          <meta name="description" content="Description of my page" />
        {/* Page content */}
  3. Clean URLs with Dynamic Routing: Utilize Next.js’s file-system-based routing to create clean and readable URLs. For dynamic routes, use getStaticPaths and getStaticProps for SEO-friendly URL structures.

  4. Image Optimization with next/image: This component optimizes images for loading speed and performance, a critical aspect of SEO.

Security Best Practices

  1. Secure Headers with next.config.js: Implement security headers like Content Security Policy (CSP) and others in next.config.js to protect your site from common vulnerabilities.

  2. Environment Variables: Store sensitive data like API keys in environment variables instead of hardcoding them in your application.

  3. Avoid Inline Script Tags: Avoid using inline script tags to prevent Cross-Site Scripting (XSS) attacks. If necessary, use nonce-based CSP.

  4. API Route Security: Secure your API routes (under pages/api) by validating and sanitizing user input, and implementing proper error handling.

Frequently Asked Questions

Below, we’ve answered some of the top questions about Next.js in web development.

What is Next JS used for?

Next.js is a React-based framework used primarily for building server-side rendered (SSR) and statically generated web applications. It’s well-suited for creating SEO-friendly, high-performance websites with optimized page loading speeds.

What is the difference between Next.js and React.js?

React.js is a JavaScript library for building user interfaces, primarily focused on the client side. It’s the core library used to develop web apps with interactive UIs.

Next.js, on the other hand, is a framework built on top of React. It extends React’s capabilities by providing additional features like server-side rendering, static site generation, automatic code splitting, and built-in CSS support.

Is Next.js a frontend or backend framework?

Next.js is primarily a frontend framework, but it blurs the line between frontend and backend development. While it’s used to build the user interface of web applications (like a traditional frontend framework), its capabilities extend to server-side functionalities, such as server-side rendering and API routes.

Is Next.js the same as Node.js?

No, Next.js and Node.js are not the same. Node.js is a JavaScript runtime that allows you to run JavaScript on the server. It’s a platform that enables server-side programming with JavaScript, which was traditionally a client-side language.

Next.js is a framework for building web applications based on Node.js. It uses Node.js for server-side operations, such as rendering pages on the server, but it specifically focuses on building web applications using React. Next.js depends on Node.js, but they serve different purposes in web development.

Building Static Pages With Next.js

Next.js acts as a superset of the React framework, extending its capabilities. With Next.js, you can perform both frontend and backend tasks. So, you can call yourself a full-stack developer after learning the framework.

In this tutorial, we explained all the features of Next.js and showed you how to install and get started with the framework. This guide should be a starting point to help you become a good Next dev.

To build on your existing knowledge, check out the following tutorials from our blog.

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David Ozokoye

David Ozokoye

Software Engineer and Technical Writer