What is Next.js?

Updated: 09/01/2022

Web applications are a fundamental part of the modern internet. As a web developer, you likely spend a lot of time trying to make the development process for these apps simpler and more efficient. That's why you should understand how Next.js works.

Next.js is a popular framework that makes it easier to develop JavaScript applications of all kinds. In this guide, you'll learn the answers to questions like, "What is Next.js?" and, "Why use Next.js?" You’ll also learn about the best use cases for Next.js in your development process. If you're ready to learn more, then let's dive in.

Next.js is a React framework that gives programmers a structured environment to quickly create fast web applications. With Next.js, you can use React’s powerful tools without having to build your application from the ground up.

React is a specific JavaScript library designed to help you develop interactive user interfaces (UIs). On its own, React is a useful tool, but it still requires a significant amount of work to use it correctly. That's why Next.js was built. But how does Next.js work?

Next.js is a React framework. The difference between libraries and frameworks is important. Libraries are just collections of useful tools. Like with a brick-and-mortar library, you're responsible for finding the specific information and tools you need. You have to call the library and tell it what you need.

In contrast, frameworks handle that for you. When you work within a framework, you don't need to worry about calling the library or pulling the tools. It acts as a frame for your application, giving it a fundamental structure and preventing errors from creeping in.

That's what Next.js does for React. The Next.js framework structures the React library and gives it a solid form. When you start a project using Next.js, the framework configures many settings behind the scenes and provides extra commands that allow you to accomplish tasks that aren't possible through the React library alone. Because of that, building applications within the Next.js framework takes less time while still offering all the benefits of the React library.

Next.js offers a broad range of functionalities. The framework was designed to provide not only structured access to the React library but also extra features. When you choose to use Next.js to build an application, you're guaranteeing that you'll have access to these functionalities.

One of the most valuable tools Next.js offers is client-side rendering. There are three ways that Next.js can render a user interface: client-side, server-side, or static site generation. Client-side rendering is the best way to make an interactive, responsive UI.

With client-side rendering, the UI is generated on the client's end of the application. The server sends basic HTML to the app along with JavaScript code. That JavaScript code contains the instructions for the app to generate the UI, including more complex HTML, in the moment.

This allows the connection between the client's device and the server to happen quickly. All of the complicated parts of the rendering the UI happen on the client's end. As a result, there's no need to constantly query the server regarding how the UI should change based on the client's actions. The UI is able to react to the client instantly, making interactive elements smoother and less prone to delays.

If interactivity isn't a primary goal of the application, then Next.js also supports static site generation. With this method, the user interface is prerendered by the server. More importantly, the server needs to generate this only once. The HTML is created and then stored in a content delivery network (CDN). Whenever that specific UI is needed, the app pulls the HTML from the CDN and presents it. There's no need for any rendering in the moment for the client or the server.

Prerendering your UI with Next.js's static site generation is a great way to automate certain parts of your process. Static pages may not be the most interactive, but they're quick to load and require no work from your own servers. This method takes some pressure off your servers and allows you to automate routine tasks like displaying loading screens, menus, and other low-interaction pages.

Part of what makes working in any framework so appealing is the way it can speed up application development. When you work with Next.js, you don't need to build your app from scratch. The framework has already laid the foundation and set the parameters for you. It even has rules and guidelines in place to help you avoid making mistakes that could cause delays or failures.

That functionality makes it easy to build your next web application quickly. Next.js helps you avoid wasting time on basic tasks and setup. Instead, you can start working on the meat of your application right away, building a complete, functional, good-looking app in less time.

It's clear that Next.js offers developers many potential tools to make applications faster and more efficient. However, the framework also impacts the user experience (UX). Next.js provides flexibility and customization options that make the UX better in three important ways:

Here's how the Next.js framework supports each of these UX elements.

Application security is a fundamental necessity for modern developers. If you don't create a secure app, your users are at risk of having their devices hacked and their information stolen. Obviously, this has a significant negative impact on the user experience.

Next.js can help make your apps more secure, particularly if you use static site generation. With static generation, there's no direct connection to any databases. User devices query the CDN instead, which provides the prerendered code. As a result, there's no easy way for hackers to inject malicious code into the database results. Users face a lower risk of malware because Next.js has stripped the need to render code on either end of the process.

Furthermore, static site generation protects user information on your servers, too. Hackers who access your web application won't be able to study its direct connection to your servers because there isn't one. There's no way for them to learn how to call your server databases and potentially access sensitive information like sign-in details or payment information.

Whether you choose static site generation or client-side rendering, Next.js can help you significantly reduce page load times. According to Google, visitors are 32% more likely to leave a webpage that takes three seconds to load compared to a page that loads in one second. Reducing page load times is a simple but valuable way to keep users engaged with your site and prevent bounces.

Static site generation means that there's no need to render a page at all. Next.js allows the next page to load significantly faster because all it needs is the HTML that the CDN provides. There's no additional rendering requirement on either end.

Client-side rendering can be almost as fast. There's no extra delay between your server and the client's device, since your server is just providing HTML and JavaScript instructions. The client's device is responsible for rendering the actual user interface. As long as the device has reasonable rendering times, the user will see the entire page significantly faster than other methods allow.

After security and speed, the third element of a great user experience is a beautiful, functional user interface. Next.js gives UX teams the ability to build a completely customized front end to fit the app's brand and target audience.

Some frameworks limit what developers can do with various elements. That's the nature of a framework: While it offers support, it also imposes limitations, just like walls in a house. However, Next.js has been carefully constructed to give developers complete freedom to customize the front end of their web applications.

That freedom means it's easy to develop appealing front-end UIs that users enjoy interacting with. There are no clunky requirements that may get in the way of your dev team's goals or needs. You can focus on providing a great experience for your users instead of fighting with the framework or reinventing the wheel.

You might still be wondering, "Why use Next.js?" It might help to understand its appeal to front-end developers. Devs using the framework appreciate it for the following functionalities.

Server-side rendering allows your web application to quickly display interactive pages that may not be easy to render on client devices. This tool lets you implement more complicated user interfaces by placing the load on your servers instead of the client's device.

Your server will generate the HTML for each request, along with JavaScript instructions for interactivity. The HTML will allow the page to quickly display a noninteractive page. After that's displayed, the JavaScript instructions will be interpreted behind the scenes to make the page interactive. In most cases, users won't notice the delay between the page appearing and the JavaScript making it functional, since they need time to decide what to click next. Meanwhile, you get to develop more complex interactive pages without risking slowing down your site.

A significant benefit of using a good framework like Next.js is the way it takes basic tasks off your plate. Next.js is structured to provide automatic compilation and bundling, meaning that it's "zero config." You don't need to do any configuration to get the framework ready for production.

Without the need to configure anything, Next.js is perfectly optimized for production from the moment you start development. That can save you significant time and prevent annoying and wasteful compilation failures. When your application is finished, all you need to do is test the compilation and bundling process once, and then move it to production. You can trust Next.js to handle the rest.

Next.js allows you to directly import CSS files from a JavaScript file. The built-in CSS parser makes it easy to import global style sheets that will apply to the entire web application. The style sheet will ensure that every part of your app is presented consistently, so you don't need to set the presentation for each element individually.

If you do have specific components that need unique CSS, that's possible too. You can import CSS Module files anywhere in an application just as easily as you would apply a global style sheet. The module will override the global style sheet in the locations you apply it to, so you can customize specific elements with ease.

This is possible because Next.js extends the import function to cover more than just JavaScript. If you choose to use the framework, this extended import functionality makes rapid development simpler and more accessible.

Next.js data fetching includes server-side rendering, client-side rendering, and static page generation. You're not limited to just one of these methods, either. While you can develop your entire application with one data-fetching technique, you can also combine them so each page of your site is generated as efficiently as possible.

For instance, you could use static generation to automate your simplest pages, such as news articles or blog posts. Meanwhile, you could use server-side generation to load your homepage, where things may frequently change but speed is of the essence. Finally, if you have a ticker page or other pages that should update without a refresh, client-side rendering is ideal. Next.js allows you to choose which pages are loaded with which method, giving you more flexibility.

Web applications rely on code splitting to function. Most web applications involve multiple pages, each of which can be visited through a specific URL. That makes every page a unique entry point to the app.

Code splitting is the process of dividing the total application's code bundle into chunks that are relevant to each page in particular. This speeds up load times by avoiding the need to render code that's irrelevant to the specific page.

Next.js automatically handles code splitting for you. The framework takes each file in the "pages/" directory and generates a specific JavaScript bundle for it, which will be called up when visitors access the page. This saves you time and effort.

Finally, Next.js gives you access to the entire React ecosystem. As a React framework, it's built to cooperate with other React components. You can use all of the features the React library offers, taking advantage of a broad range of tools to make your UI more appealing.

If you're still not sure about whether Next.js is right for your application, it might help to understand the situations in which the framework really shines. Some of the best opportunities to use Next.js include the following.

If you have a software-as-a-service (SaaS) product that you want to expand, time is of the essence. Both development time and page load times are essential factors when you're trying to make your SaaS product more appealing. Next.js helps you trim the time wasted on both of these issues.

You can use Next.js to build out new SaaS features and products in less time. The framework will help you move from idea to finished product without having to waste time on configuration and bundling. Meanwhile, the data -fetching options allow you to build an application that loads faster on every page.

Similarly, Next.js is a great way to build new web applications and portals. Paired with the right Next.js authentication solution, the static site generation feature helps you build fast-loading pages that allow your users to quickly sign into the app or portal. You can even implement multifactor authentication in your portal to strengthen your security and protect your users' data.

Next.js is structured to make interactivity a priority for the user interface. Whether you use server-side or client-side rendering, you can produce highly interactive webpages that load in less time. Each page can be built with the rendering method that allows for the most efficient interaction.

Furthermore, the ability to customize your front end makes Next.js a valuable tool for developing a unique UI that's interactive in the ways you need. You're not stuck trying to build an application around the framework's assumptions. The result is a front-end UX that's ideal for any interactive application.

If you're interested in using Next.js in your development environment, Clerk can help. Clerk offers the easiest solution for Next.js authentication on the market. Learn more about how you can keep your Next.js application secure and accelerate your development with Clerk's Next.js authentication tool today.