Avoiding Memory Leaks and Performance Bottlenecks in Next.js Applications

Let me tell you a quick story. A few months ago, I built a high-traffic dashboard with Next.js, and everything looked perfect until it wasn’t. After just a few days in production, users started complaining about slow loading times, freezes, and even crashes. I dove into debugging and guess what? The culprit was memory leaks.

If you’re a developer like me, constantly shipping features and fixing bugs, it’s easy to overlook how unmounted components or lingering event listeners can quietly hog memory in the background. In this post, I’ll walk you through how I identified these issues and the techniques I use now to avoid memory leaks and performance bottlenecks in my Next.js apps.

1. Understanding What Causes Memory Leaks in Next.js

Memory leaks happen when your app holds onto resources that are no longer needed. Here are some common culprits I ran into:

• Event listeners not removed
• Intervals or timeouts not cleared
• Global state persisting too long
• Refs to DOM nodes that were removed
• Improper use of closures

Real Issue I Faced

I had a window.addEventListener(’resize’, handler) inside a component but forgot to remove it in useEffect cleanup. After navigating back and forth, the listeners piled up and wrecked performance.

2. Using useEffect Properly

When I first started with React hooks, I didn’t fully understand how crucial cleanups in useEffect were. Now, I always make sure to clean up side effects:

useEffect(() => {

  const handler = () => console.log("resizing");

  window.addEventListener("resize", handler);

 

  return () => {

    window.removeEventListener("resize", handler);

  };

}, []);

This little return function inside useEffect is what saved my app from bloating.

3. Monitoring with Chrome DevTools and Performance Profilers

When things feel off, I use Chrome DevTools’ Performance tab to spot memory usage over time. Here’s what I do:

• Record a session during interaction.
• Check for steady memory growth without drop.
• Identify long-running timers, intervals, or detached DOM nodes.

For more in-depth profiling, I also use React Profiler to identify slow components and re-renders.

4. Avoiding Anonymous Functions in JSX

I used to write stuff like this:

<button onClick={() => doSomething()}>Click</button>

Not a huge issue on its own, but in lists or high-frequency renders, it slows things down. Now I memoize handlers outside render when needed:

5. Global State Management Pitfalls

Using tools like Redux, Zustand, or Recoil is great but be careful. I’ve seen global states keep references to data long after it’s needed.

Tip:

Clear unused states when navigating or unmounting components. In Zustand, I use set(() => initialState) when I know the data is stale.

6. Lazy Load and Dynamic Import Wisely

Next.js supports dynamic imports, and they’re a blessing. I started using them to split code:

const HeavyComponent = dynamic(() => import("../HeavyComponent"), { ssr: false });

This keeps the initial load light and avoids choking the main thread.

7. Throttle or Debounce Expensive Calls

When I had scroll and resize listeners firing dozens of times a second, I learned to debounce:

const debouncedHandler = useMemo(() => debounce(myFunc, 300), []);

Wrap-Up

Don’t wait for users to complain like I did. Start profiling early, clean up effects, and manage state smartly. Next.js gives us powerful tools but it’s on us to use them wisely.