In the realm of web development, speed and efficiency are paramount. One technique to enhance user experience is prefetching, a feature that Next.js leverages to make navigation faster and smoother. In this blog post, we will dive into how prefetching works in Next.js, its benefits, and how you can control it in your application.
Client-Side Navigation Recap
Before we delve into prefetching, it's important to understand client-side navigation. Using the Link component in Next.js allows us to navigate between pages without reloading the entire page. This is achieved by dynamically updating the content on the current page, making the navigation instant and seamless.
What is Prefetching?
Prefetching is a technique where the browser fetches resources (such as data or scripts) in advance, anticipating that the user might need them soon. In the context of Next.js, prefetching allows the framework to load data for linked pages even before the user clicks on them.
How Prefetching Works
When you hover over a link in a Next.js application, the framework can make a request to fetch data for the target route. This is done to ensure that when you eventually click the link, the content is already available, resulting in instantaneous navigation.
Prefetching in Development vs. Production
In development mode, Next.js prefetches data when you hover over a link. However, in production, the behavior is slightly different. Let's explore this by building our application and observing the network requests.
Building and Running the Production Server
To see prefetching in action, we need to build and run our application in production mode:
Build the Application:
npm run build2. Start the Production Server:
npm startOnce the server is running, let's navigate to the home page and inspect the network requests.
Observing Prefetching
When the initial page loads, you'll notice a few network requests. Filtering the requests to show only HTML documents reveals that only a single HTML document is loaded for the initial page.
However, if you filter the requests to show fetch operations, you will see additional requests for each link in the navigation bar. These requests are not fetching full HTML documents but rather data used by React Server Components. This data contains all the information needed to render the target page, making subsequent navigation instantaneous.
Controlling Prefetching
While prefetching enhances performance, there might be scenarios where you don't want to prefetch certain links. For example, if a particular page is large and rarely visited, you might want to disable prefetching for that link.
To disable prefetching for a specific link, you can set the prefetch prop to false on the Link component:
import Link from 'next/link';
export default function RootLayout({ children }) {
return (
<html lang="en">
<body>
<header>
<nav>
<ul>
<li><Link href="/">Home</Link></li>
<li><Link href="/reviews">Reviews</Link></li>
<li><Link href="/about" prefetch={false}>About</Link></li>
</ul>
</nav>
</header>
<main>{children}</main>
</body>
</html>
);
}Testing the Changes
After making this change, rebuild your application and restart the production server. When you load the home page, you will notice that the data for the "About" page is no longer prefetched. Instead, the data for this page is only fetched when you actually click the link, resulting in a new network request.
Even without prefetching, the request for the "About" page data is smaller than a full HTML document, making it faster to load.
Conclusion
Prefetching in Next.js significantly enhances the user experience by making navigation between pages almost instantaneous. By default, Next.js prefetches data for all links on the initial page load, but you have the flexibility to disable this behavior for specific links if needed.
Understanding and utilizing prefetching can make your Next.js applications more efficient and responsive, providing a smoother experience for your users.
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