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Optimizing Next.js Build Performance: Strategies for Faster Web Apps

Posted on: Nov 22, 2023

12 mins read

Originally published at blog.logrocket.com

Optimizing Next.js Build Performance: Strategies for Faster Web Apps

Creating modern web applications is tough, especially as they get bigger. To keep your app running fast, you need to think about performance from the start. Luckily, frameworks like Next.js, a popular choice for React, make building robust web apps a breeze.

Next.js packs in features like server-side rendering, static site generation, and easy file-based routing. Plus, it has built-in optimizations to speed up your app. In this article, we'll check out some simple ways to make your Next.js app build even faster.

What is build performance?

Build performance is the time it takes to build your application, i.e., compile and generate the static files. A fast build performance is vital because it allows you to iterate faster and deliver your application to your users more quickly.

Many factors can affect the build performance of your application, including the size of your application, the number of dependencies, the number of pages, and the number of components. If the build performance of your application is slow, the overall performance of your application will be affected, thus affecting the user experience of your application.

By default, Next.js provides many optimizations to improve your application's build performance. And there are other things you can do too to improve the build performance of your application. Let's look at some of them.

Optimizing the build performance of your Next.js application

The following are some of the ways to optimize the build performance of your Next.js application:

Use the latest stable version of Next.js

The easiest way to improve the build performance of your Next.js application is to use the latest stable version of Next.js. Next.js is a fast-growing framework, and the team behind it is constantly working on improving the framework. New features and optimizations are continually added to it. Hence, it is vital to use the latest stable release.

As of the writing of this article, the latest stable version of Next.js is v13.4. (You can check the latest stable version of Next.js here). You can also upgrade your application to the latest stable version of Next.js by running the following command:

bash
npm install next@latest

Use Next.js built-in optimizations

As I mentioned earlier, Next.js provides you with many built-in optimizations to improve the build performance of your application. Some of these optimizations include:

  1. Automatic Static Optimization: By default, Next.js will automatically render your application as static HTML if there are no dynamic routes in your application. This is determined by whether the page has getServerSideProps or getInitialProps defined. If they are not, Next.js will not need to re-render the page on every request, as pages will be built once and served to all users.

    This improves the performance of your application by reducing the time it takes to generate the static HTML for your application. It is perfect for web applications without dynamic routes and pages that only change sometimes.

    For pages that do have dynamic routes or fetch data from an external API, using Next.js's getServerSideProps or getInitialProps functions will allow you to prerender the page on the server and fetch the necessary data before sending the HTML to the client. It helps improve the initial load time and overall performance of the page.

  2. Automatic Code Splitting: Code splitting is the process of splitting your code into smaller chunks. Each chunk contains the code needed for a particular page. By default, Next.js will automatically break your code into smaller chunks to reduce the time it takes to load the code for your application. So, Next.js will only load the code needed for that particular page on the initial page load.

    To further utilize the benefits of code splitting, you can use dynamic imports to load the code for a particular page only when needed. Code splitting is helpful for pages that are visited infrequently. For example, if you have a page only seen by a few users, you can use dynamic imports to load the code for that page only when needed.

  3. Automatic Image Optimization: Using the next/image component, Next.js built-in <img> element, you can benefit from Next.js automatic image optimization. Next.js will automatically optimize your images by lazy loading and automatically resizing/compressing images based on device size. Lazy loading is the process of loading images only when they are needed, i.e., when they are visible on the screen. Automatic Image Optimization reduces the time it takes to load the images in your application, improving your application's performance.

    You can also indicate to Next.js that you want some images to be loaded initially by setting the priority prop on the next/image component to true. Next.js will prioritize loading the essential images you want to load first.

  4. Automatic Font Optimization: Next.js also optimizes font using the next/font component. This component includes built-in automatic self-hosting for Google Fonts. You can use Google Fonts in your application without having to worry about "layout shift" or "flash of invisible text"(FOIT).

    What Next.js does is that it will automatically download the fonts and serve them from your application. So the fonts will be available to your users even offline. It cuts down on the time it takes to load the fonts in your application, improving your application's performance.

  5. Automatic Prefetching: Prefetching means loading the code for a particular page before the user navigates to that page. By default, Next.js will automatically prefetch the code for the page the user will likely visit next if you use the Link component from next/link. So when the initial page is loaded, the visible links on the screen are prefetched. It is handy for pages that are visited often.

    For pages that are not visited often, you can use the prefetch prop on the Link component and set it to false to disable prefetching for that page. So only when the user hovers over the link will the code for that page prefetch. Depending on the use case of prefetch, you can improve the performance of your application, reducing the time it takes to load the code for the next page.

  6. Optimizing third-party scripts: Next.js provides you with next/script component to load third-party scripts. By default, the next/script component allows you to load scripts early but after some critical content has loaded to prevent blocking the page load.

    Next.js also ensures that a script is only loaded once. It is beneficial for scripts used across multiple pages in your application. It means that even when the user navigates to a page that does not use the script, the script will not be loaded again when they navigate to a page that uses it.

Critical Rendering Path Optimization

The Critical Rendering Path (CRP) refers to browsers' steps to convert HTML, CSS, and JavaScript into a rendered webpage. Optimizing the Critical Rendering Path is essential for improving a web application's initial load time and perceived performance. CRP optimization involves optimizing the delivery and rendering of the most critical content to the user as quickly as possible. By minimizing the time it takes for the browser to render the page, you can improve the perceived performance and provide a better user experience.

The following are some techniques for optimizing CRP:

  1. Optimize Large Contentful Paint: Large Contentful Paint (LCP) is a Core Web Vitals metric for measuring the time it takes for the largest content element in the viewport to become visible. LCP is crucial because it measures the perceived load speed of your application. Utilizing tools like Lighthouse and PageSpeed Insights can help you identify opportunities to improve the LCP of your application. Some of the ways to enhance the LCP of your application include:

    • Minimize render-blocking resources: Render-blocking resources block the browser from rendering the page. These resources include CSS and JavaScript files. By minimizing the number of render-blocking resources, you can improve the LCP of your application.
    • Minimize main thread work: The main thread parses HTML, executes JavaScript, and renders the page. By minimizing the amount of work done on the main thread, you can improve the LCP of your application.
    • Reduce JavaScript execution time: JavaScript is a single-threaded language, meaning that only one task executes at a time. By reducing the amount of JavaScript executed on the main thread, you can improve the LCP of your application.

    Using async and the next/script component to load your scripts can also help improve the LCP of your application by allowing the browser to download the script asynchronously without blocking the rendering of the page.

  2. Use Intersection Observer API: The Intersection Observer API is a browser API that allows one to observe changes in the intersection of a target element with its ancestor element or a top-level document's viewport. It is helpful for lazy loading images and other content not visible on the screen. By using the Intersection Observer API, you can improve the LCP of your application by loading contents only when they are visible on the screen.

  3. CSS and JS Optimization and Minification: CSS and JavaScript optimization and minification remove unnecessary characters from your CSS and JavaScript files without changing their functionality. Avoid using CSS prepossessors that add unnecessary characters to your CSS files. You can also use tools like PurgeCSS to remove unused CSS from your application. It will reduce the size of your CSS files, improving the LCP of your application.

    Similarly, avoid using unnecessary characters in your JavaScript files. Tools like Terser also help you to minify your JavaScript files, reducing their size and improving the LCP of your application.

Improving Network Performance

Improving network performance is another way to improve the build performance of your Next.js application. Network performance is the time it takes for the browser to download the resources for your application. The following are some ways to improve the network performance of your application:

  1. Caching: Caching stores the resources for your application in the browser. Implementing caching strategies like Cache-Control headers and Service Workers can help improve the network performance of your application. Cache-Control headers allow you to specify browser caching policies like how long to cache a resource and when to revalidate the resource. Next.js enables you to set the Cache-Control headers for your application by using the headers property in the next.config.js file.

    Service Workers allow you to cache resources in the browser and serve them from the cache when the user is offline. It reduces the time it takes to load the resources in your application, hence, improving the network performance of your application.

  2. CDN Integration: A Content Delivery Network (CDN) is a network of servers distributed globally. You store your static assets on these servers, which get delivered to users based on location. You can cache static assets and serve them from edge locations using a CDN for faster global delivery.

    Next.js also provides built-in support for Vercel Edge Network. If you use Vercel for deployment, you automatically use the Vercel Edge Network as a CDN.

Bundle analysis

Bundle analysis is analyzing your application to identify opportunities to reduce its size. When you use a bundle analysis tool, you see what modules in your application bundle take up much space. You identify unnecessary files and then find ways to reduce the size of such files or delete unused ones. Some tools for analyzing the size of your Next.js application include next/bundle-analyzer, webpack-bundle-analyzer, and next-bundle-analyzer.

Dependency management

Managing the dependencies in your application is another way to improve the build performance of your application. By removing unused dependencies and optimizing the dependencies in your application, you can enhance its build performance. The following are some ways to maximize your application's dependencies:

  1. Remove unused dependencies: Using tools like depcheck in your application can help identify unused dependencies. You can then uninstall them, reducing your application's size and improving its build performance.
  2. Tree Shaking: Tree shaking is the process of removing unused or dead code from the final bundle of your application. Next.js has built-in support for tree shaking. You should use ES6 modules instead of CommonJS modules to take advantage of this. i.e., use import and export statements instead of require and module.exports statements.
  3. Specific Imports: You should import only the module parts you need when importing a module. It is handy for modules that have a lot of exports. For example, instead of importing the entire module like this:
js
import { Button, Card, Input } from "react-bootstrap";

You can import only the parts of the module that you need, like this:

js
import Button from "react-bootstrap/Button";
import Card from "react-bootstrap/Card";
import Input from "react-bootstrap/Input";

Excluding unnecessary folders or files from the build

Another way to optimize the build performance of your Next.js application is by excluding unnecessary folders or files from the build process. You can reduce the build time and improve overall performance by excluding specific directories or files not required for rendering your application.

Configure the build process to exclude specific directories or files using the exclude option in the next.config.js file. Doing this allows you to specify patterns or paths that should be ignored during the build. For example, you can exclude folders containing large media files, documentation, or development-specific assets that are not necessary for the production build.

js
module.exports = {
exclude: ["**/media/**", "**/docs/**", "**/dev/**"],
};

By excluding these unnecessary resources from the build, you reduce the amount of data that needs to be processed and bundled, resulting in faster build times and more efficient resource utilization. This optimization technique is advantageous when dealing with large projects or when you have specific folders or files that don't contribute to the rendering, thus, omitting them safely.

Conclusion

In conclusion, making your Next.js app build faster is key for a quick and smooth user experience. Take advantage of Next.js's built-in optimizations and apply strategies like Critical Rendering Path optimization, Network performance tweaks, and smart Dependency management. Keep a close eye on your app's performance with regular monitoring and testing to spot areas for enhancement, ensuring your app stays consistently speedy.

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Frequently Asked Questions

1. Why is build performance important for a Next.js application?

Fast build performance ensures quicker development iterations and faster delivery of your application to users. It impacts the overall user experience.

2. How can I check the current version of Next.js for updates?

You can check the latest stable release of Next.js on its GitHub releases page: Next.js Releases

3. What are some benefits of using Automatic Static Optimization in Next.js?

Automatic Static Optimization improves performance by rendering pages as static HTML, reducing the need for repeated rendering on each request.

4. How does Next.js prefetching work, and when should I use it?

Next.js automatically prefetches code for the page the user is likely to visit next, enhancing performance. You can control prefetching using the Link component.

5. What is Critical Rendering Path Optimization, and why is it crucial?

Critical Rendering Path Optimization focuses on delivering and rendering critical content quickly, improving a web app's initial load time and perceived performance.

6. How does Bundle Analysis help in optimizing the size of a Next.js application?

Bundle Analysis tools like next/bundle-analyzer help identify large modules in your app, enabling you to reduce size by eliminating unnecessary files.

7. What role does caching play in improving the network performance of a Next.js app?

Caching, through strategies like Cache-Control headers and Service Workers, stores resources in the browser, reducing the time it takes to load them and enhancing network performance.

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