How to optimize the performance of your Next.js app

According to the Stack Overflow 2024 survey, approximately 18% of developers use Next.js, making it a popular choice. While many are familiar with its basic optimizations, some advanced techniques aren't as widely known. These approaches can significantly improve your app's performance and offer a smoother experience for users.

Let's explore some unique methods that go beyond common practices and help you get the most out of your Next.js app.

Implement Server-Side Rendering (SSR) caching for dynamic data

For applications that rely on server-side rendering, caching can significantly speed up response times for dynamic content. Typically, every request results in fresh content being generated, which can cause delays, especially under high traffic or with complex data.

One solution is page-level caching, where the server stores pre-rendered pages and delivers them quickly without regenerating the same content repeatedly. Periodically refreshing cached pages in the background ensures users still get relatively fresh content without taxing your server for every request.

Setting cache control headers helps manage how long pages are stored and when updates are needed, allowing even dynamic pages to load quickly and efficiently.

Efficient data fetching with "stale-while-revalidate"

Fetching data from external APIs can be slow, especially if the data doesn't change often. Instead of requesting fresh data on every page load, you can adopt the "stale-while-revalidate" strategy. This method serves cached data instantly while updating it in the background. Existing data allows for quick responses for users, and any new data is stored for future requests.

Use this strategy in scenarios where real-time updates aren't necessary. For example, news websites or product listings can benefit from this, as users will see slightly outdated content immediately, and the updated data will be available the next time they visit.

The key here is to define revalidation intervals, how often the data should be refreshed, and how to serve cached data in the meantime.

Reducing JavaScript bundle size for faster load times

A bloated JavaScript bundle can be a silent culprit behind slow page loads. Every extra kilobyte of unnecessary code adds to the time it takes for a user to fully interact with your app. To address this, you can analyze your JavaScript bundle to identify large or redundant parts of your code.

Developers often import entire libraries or components even when they are used sparingly. To fix this, you can load these components or libraries conditionally. This means the component only loads when a user interacts with a specific feature, significantly cutting down the initial load time.

This method of reducing bundle size, sometimes referred to as "code splitting," ensures that users download only the necessary code for the current page they're visiting. It makes your app feel more responsive because less data needs to be transferred.

Prioritize loading of key resources

While lazy loading is widely adopted to improve performance, certain key assets, like above-the-fold images or critical fonts, need to load as fast as possible. A little-known method to prioritize these assets is by marking them as high priority. This prompts the browser to load these critical assets before others, ensuring that essential elements are visible immediately.

For instance, you can assign priority to an image that plays a central role on the landing page, making sure it loads before other, less important elements. This improves the user’s experience since the main content is displayed quickly, even if other parts of the page are still loading.

Similarly, prioritizing fonts that are central to your design helps maintain the layout without any delay or "flash of unstyled text," improving the overall experience.

Edge functions for faster response times

One of the lesser-utilized techniques is deploying certain parts of your app closer to your users using edge computing. Edge functions enable running code on servers close to the user's location. It helps cut down the time required for requests to reach the main server and return.

You can offload tasks like authentication checks or geolocation-based content at the edge. Using this approach ensures that lightweight processes are handled closer to the user, which cuts down on the delay caused by longer round trips to a centralized server.

Platforms like Vercel or Cloudflare allow you to set up these edge functions, improving the overall performance of your application, especially for users who are far from your primary server.

Preloading and pre-fetching critical resources

Another often overlooked optimization is preloading or pre-fetching critical resources before they're needed. Loading essential assets, like fonts, key images, or even future page content, ahead of user interaction can significantly improve performance.

For example, if you know that users will likely click a certain link or navigate to a specific page, you can pre-load the assets for that page in the background. By the time the user interacts with that content, it's already available, making the page feel faster and more responsive.

The tactic proves especially helpful for single-page applications, ensuring a smooth experience as users move between different sections.

Preloading key elements and pre-fetching future content speeds up navigation and ensures users don't experience delays when moving between different sections of your app.

Which one of these tips have you put to the test? Or did you have a Next.js hack that we missed? Share your insights in the comments.