Avoid These Lazy Loading Mistakes That Could Slow Down Your Website (with Real Fixes)

Stop Hurting Your Page Speed: Common Lazy Loading Mistakes & How to Fix Them

Lazy loading is everywhere — and for good reason. It boosts performance by loading only what the user needs. But here’s the twist: done wrong, it can backfire badly.

In this post, I’ll break down the real mistakes developers make with lazy loading (yes, even you might be doing this) and show you how to fix them with real-world examples from production React and Next.js apps.

But here’s the twist:

⚠️ Lazy loading done wrong can make your site feel slower_, not faster._

This post is about the dark side of lazy loading  — especially in React and Next.js  — and how it could still be killing your performance if you’re not careful.

🚨 The Real Problem: Lazy ≠ Light

Let’s break a common myth:

💬 “If I lazy-load a component, it won’t affect performance.”

Wrong.

Lazy-loaded chunks still:

• Need to be fetched over the network (possibly competing with more important requests).
• Must be parsed + executed (which can be heavy on low-end devices).
• Need to be hydrated in React (which blocks interactivity).

🔍 The Illusion of Lazy Loading — A Real Example

Let’s say you have a typical Next.js marketing site. Your homepage has:

• A Hero section (static)
• A Testimonials carousel (client-side interaction)
• A Newsletter Form with validation
• A TeamGrid that fades in

Being a good dev, you lazy-load non-critical components like this:

// pages/index.tsx

import dynamic from 'next/dynamic';

const Testimonials = dynamic(() => import('../components/Testimonials'), {
  ssr: false,
});
const NewsletterForm = dynamic(() => import('../components/NewsletterForm'), {
  loading: () => <Spinner />,
});
const TeamGrid = dynamic(() => import('../components/TeamGrid'));

export default function Home() {
  return (
    <main>
      <Hero />
      <Testimonials />
      <NewsletterForm />
      <TeamGrid />
    </main>
  );
}

You test locally and see:

✅ Smaller main bundle

✅ Fewer components in the server-rendered HTML

✅ Lighthouse first paint improved by ~10%

Feels like a win… right?

Not quite.

📉 What Actually Happens in Production

On a real device (especially on 3G/4G):

1. Initial paint is faster , yes.
2. But then, several lazy-loaded components all start fetching at once.
3. Once loaded, they hydrate together , creating a hydration bottleneck.
4. JS parsing, validation logic, carousel libraries —  all fight for the main thread.

🧪 Performance Snapshot

Using React Profiler + web-vitals + Chrome DevTools:

Despite the smaller initial bundle, lazy-loading too much actually delayed full interactivity .

💥 The Trap: Lazy Loads Hydrate All at Once

React doesn’t stagger hydration. If you load multiple lazy components at once, hydration tasks stack and execute together , making the UI janky or unresponsive during that window.

Even worse: if your components rely on libraries like react-slick, react-hook-form, or animation frameworks, their client-side-only logic loads in bulk.

✅ How to Fix It: Smarter Lazy Loading in React

Let’s address the real-world issues from Part 2 using 3 practical approaches.

1️⃣ Defer Lazy Components Until User Interaction

Lazy load isn’t just about splitting code — it’s about timing.

Use IntersectionObserver to defer hydration until the component enters the viewport :

import dynamic from 'next/dynamic';
import { useInView } from 'react-intersection-observer';

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

export default function Home() {
  const { ref, inView } = useInView({ triggerOnce: true });

  return (
    <>
      <Hero />
      <div ref={ref}>{inView && <Testimonials />}</div>
    </>
  );
}

⏳ Result: The component is only hydrated when it’s about to be visible.

2️⃣ Stagger Hydration with requestIdleCallback

You can delay hydration tasks until the browser is idle:

useEffect(() => {
  if ('requestIdleCallback' in window) {
    requestIdleCallback(() => import('./NewsletterForm'));
  } else {
    setTimeout(() => import('./NewsletterForm'), 2000);
  }
}, []);

🧠 This avoids blocking the main thread during initial load.

3️⃣ Use Next.js App Router + use client Modules Strategically

In the App Router (app/), isolate only the dynamic pieces inside use client boundaries:

// app/components/ClientWrapper.tsx
'use client';

import { NewsletterForm } from './NewsletterForm';

export default function ClientWrapper() {
  return <NewsletterForm />;
}

Then lazy-load just this:

const NewsletterForm = dynamic(() => import('./components/ClientWrapper'), {
  ssr: false,
});

🎯 Keeps the static parts server-rendered, and only the interactive part runs client-side.

🧪 Bonus: Preload Strategically

<link rel="modulepreload" href="/_next/static/chunks/components_Testimonials.js" />

Or if using dynamic imports:

import('../components/Testimonials'); // preload early in useEffect

Preloading reduces perceived delay without bloating your initial bundle.

🚀 TL;DR: Lazy Load Responsibly

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