Next.js Performance Optimization: How to Increase Next.js Speed

Performance is crucial for any website. Everyone prefers a faster website. Next.js apps are fast and optimized by default. However, if the app size grows, there is a chance for lower performance. I will guide you on optimizing your Next.js app from a small scale to a large one. This can also improve your SEO.

Importance of performance optimization

Performance optimization is essential for several reasons: You can check the Next.js documentation.

1. User Experience: Websites that load quickly offer a superior user experience. Visitors are more inclined to remain on and engage with a site that loads swiftly, resulting in higher engagement and reduced bounce rates.

2. SEO Benefits: Page speed affects your web page rank in the Google. Enhanced performance can boost your site's visibility in search engine results, attracting more organic traffic.

3. Conversion Rates: Research indicates that even a one-second delay in page load time can significantly decrease conversions. Faster websites can lead to increased sales and improved user retention.

4. Mobile Users: With the growing use of mobile devices, optimizing performance becomes even more crucial. Mobile networks can be slower and less reliable, so ensuring speed optimization provides a smoother experience for mobile users.

5. Resource Efficiency: Optimized websites consume fewer server resources, which can lower hosting costs and enhance scalability. Efficient code and assets result in reduced bandwidth usage and faster load times.

6. Competitive Advantage: In a competitive market, a faster website can distinguish you from competitors. Users are more likely to choose a site that offers a seamless and quick experience.

7. Accessibility: Performance optimization can also enhance accessibility. Faster load times and efficient resource usage make your site more accessible to users with slower internet connections or older devices.

Nextjs Optimization

Next.js offers several built-in features and functionalities that contribute to optimization by default. Here are some key areas it handles:

1. Automatic Code Splitting:

• Next.js intelligently breaks down your JavaScript codebase into smaller bundles.

• Only the necessary code for the initial page load is included, reducing initial payload size and improving load times.

• Unused code from other pages is loaded on demand when the user navigates, enhancing overall performance.

2. Static Site Generation (SSG):

• Next.js enables pre-rendering of your application's HTML at build time.

• This static HTML can be served directly, bypassing the need for server-side rendering on every request.

• This approach is ideal for content that doesn't change frequently, resulting in faster load times.

3. Server-Side Rendering (SSR):

• Next.js also supports SSR for dynamic content or situations where SEO is crucial.

• The server renders the HTML on each request with the latest data, ensuring search engines can properly index your content.

4. Image Optimization:

• The built-in Image component automatically optimizes images for you. It generates multiple image source sets tailored for various devices.

• It implements techniques like lazy loading, responsive resizing, and format conversion (WebP, AVIF) to reduce image file size and improve loading speed.

5. Routing Optimization:

• Next.js utilizes client-side routing by default, providing a seamless user experience with smooth transitions between pages.

• This approach minimizes server interaction and reduces page load times.

Additional Optimizations:

• Next.js also offers features like automatic font optimization with next/font and script loading control with next/script.

• These components further contribute to streamlining your application's performance.

By leveraging these built-in functionalities, Next.js helps you create performant web applications out of the box. However, there's always room for further optimization based on your specific needs. Techniques like code-splitting customization, caching strategies, and external library management can be explored for even greater performance gains.

Dynamic imports

Dynamic imports enable the asynchronous loading of JavaScript modules, ensuring that a module is only loaded when it is needed rather than during the initial load time. This means that a module is only loaded when it is needed, rather than at the initial load time. In Next.js, you can use the next/dynamic module to achieve this. For example:

import dynamic from 'next/dynamic';

const DynamicComponent = dynamic(() => import('../components/DynamicComponent'));

function HomePage() {
  return (
    <div>
      <h1>Welcome to the Home Page</h1>
        {
           condition &&  <DynamicComponent /> // Here the component loads when condition is true
        }
    </div>
  );
}

export default HomePage;

Critical CSS and Purging Unused CSS

For better performance, it is advisable to remove any unused CSS. You might also find it helpful to use tools like PurgeCSS to automate this process. You can refer to the PurgeCSS documentation for more information.

Import on demand

Import on demand allows you to load JavaScript only when needed, significantly improving your bundle size and performance. In Next.js, you can achieve this as follows:

const onSubmit = async (formData) => {
	const { default: axios } = await import("axios"); // Loads axios when someone submits the form.
	try {
		const res = await axios.get("url");
		console.log(res);
	} catch (error) {
		console.error(error);
	}
};

Increase Image Cache Duration

Images significantly affect page load speed. Images which are in our controlled can be compressed to smaller size before using in application but Images fetching from APIs, we can't say anything about that, but we can increase it's cache duration in our application.

To increase the next/image cache duration, copy the following code and paste in next.config.js

/** @type {import('next').NextConfig} */
const nextConfig = {
    images: {
		minimumCacheTTL: 86400, // Cache for 1 day
    }
}

This configuration will cache the image for 1-day which can significantly improve the performance of your Next.js application by reducing the need to re-fetch images from the server.

Analyzing Bundle Size with next-bundle-analyzer

To understand and optimize your bundle size, you can use the next-bundle-analyzer plugin. This tool gives you a visual map of your bundle, showing the size of each module. It helps you find large or unnecessary dependencies.

First, install the plugin:

npm install @next/bundle-analyzer

Then, configure it in your next.config.js:

import BundleAnalyzer from "@next/bundle-analyzer";

const withBundleAnalyzer = BundleAnalyzer({
	enabled: process.env.ANALYZE === "true",
});

const nextConfig = {};

export default withBundleAnalyzer(nextConfig)

To generate the bundle analysis, run the build command with the ANALYZE environment variable set to true:

ANALYZE=true npm run build

This will generate a report that you can use to identify and optimize large modules in your bundle.

By implementing these strategies, you can significantly reduce the size of your JavaScript bundles, leading to faster load times and a better user experience for your Next.js application.

Performance Monitoring Tools

You need to regularly monitor your website's performance using tools like GTmetrix and PageSpeed Insights. These tools show the performance of your web application, including factors affecting your performance metrics such as LCB, TTB, and FCP.

Here is my website's performance in GTmetrix.

GTmetrix gave my website an A grade, which is the best. All other results, such as performance structure, LCP, TBT, and CLS, are as minimal as possible.

PageSpeed Insights provides the perfomance results for both desktop and mobile. Here is my website performance in PageSpeed Insights.

For Desktop :

My performance, accessibility, best practices, and SEO scores are all 100%, indicating that there is little room for further improvement.

For Mobile

My performance score is 81%, but my accessibility, best practices, and SEO scores are all 100%, indicating that there is some room for improvement in performance.

Summary

Performance optimization is vital for enhancing user experience, SEO, conversion rates, mobile user engagement, resource efficiency, competitive advantage, and accessibility. Next.js offers built-in features like automatic code splitting, static site generation (SSG), server-side rendering (SSR), image optimization, and routing optimization to improve performance. Additional strategies such as dynamic imports, critical CSS and purging unused CSS, import on demand, and analyzing bundle size with `next-bundle-analyzer` can further enhance your Next.js application's speed and efficiency.