LWC lazy loading: Improve performance and load times

Posted by Vinay Vernekar 25th September 2025

If you’ve ever built a complex page in Salesforce, you know the pain of a slow load. That’s where LWC lazy loading comes in to save your users from staring at a spinner while the browser chokes on massive JavaScript bundles. It’s a simple idea: don’t load what you don’t need right away. By deferring components, scripts, or images until they’re actually in view or requested, you make your apps feel snappy and professional.

Why you should care about LWC lazy loading

I’ve seen teams build massive “all-in-one” components that try to fetch everything on the first render. It’s a performance killer, especially for users on mobile or slow office Wi-Fi. When you implement LWC lazy loading, you’re looking at much faster initial rendering and a better Time to Interactive (TTI). Why force a user’s browser to download a heavy charting library if they never even click on the “Reports” tab?

It isn’t just about speed, either. It’s about being smart with resources. Lower bandwidth and CPU usage mean a smoother experience across the board. If you’re working on LWC component communication between several heavy child components, lazy loading ensures you aren’t overloading the DOM all at once.

How to implement LWC lazy loading in your projects

There are a few ways to pull this off depending on what you’re trying to hide. Let’s break down the most common patterns I use in my day-to-day work. Here’s the thing: you don’t always need the most complex solution. Sometimes the simplest trick is the best one.

1. Conditional rendering with template if:true

This is the bread and butter of LWC lazy loading. If a component is wrapped in a template if:true, Salesforce won’t even try to create it until that condition becomes true. This is perfect for modals or tabs that aren’t visible by default.

// parentComponent.js
import { LightningElement } from 'lwc';
export default class ParentComponent extends LightningElement {
  showDetails = false;

  handleToggle() {
    this.showDetails = true; // The child only exists in the DOM after this
  }
}

// parentComponent.html
<template>
  <button onclick={handleToggle}>Load Details</button>
  <template if:true={showDetails}>
    <c-heavy-detail-view></c-heavy-detail-view>
  </template>
</template>

2. Dynamic imports for heavy modules

Now, if you want to get fancy, you can use JavaScript dynamic imports. This actually splits your code into separate chunks. Instead of the browser downloading one giant JS file, it only grabs the “heavy” part when you call the import. This is a massive win for LWC lazy loading efficiency.

async loadSpecialFeature() {
  // The browser fetches this file only when this function runs
  const { MyHelper } = await import('c/helperModule');
  MyHelper.doSomethingCool();
}

3. Using IntersectionObserver for viewport loading

This is probably the most overlooked feature for long pages. Why load a footer or a bottom-page widget if the user never scrolls down? You can use the browser’s IntersectionObserver to detect when a container enters the screen. If you’re looking for more tips on handling how things move on the screen, check out this guide on Master LWC element scrolling.

renderedCallback() {
  if (this.hasStartedObserving) return;
  
  const observer = new IntersectionObserver((entries) => {
    if (entries[0].isIntersecting) {
      this.isComponentVisible = true;
      observer.disconnect();
    }
  });

  observer.observe(this.template.querySelector('.trigger-point'));
  this.hasStartedObserving = true;
}

4. Loading third-party libraries on demand

Don’t load D3.js or Chart.js in your connectedCallback if the user hasn’t opened the chart view. Use loadScript and loadStyle only when the user triggers the action. It keeps your initial page weight light and prevents the “frozen screen” feeling during page load.

Pro Tip: Always use a flag like “isLibraryLoaded” to prevent your code from trying to download the same script multiple times if a user clicks a button twice.

Avoiding the “Lazy” traps

But wait, you can definitely overdo this. One thing that trips people up is “spinner fatigue.” If every single click on your page triggers a new loading spinner because you lazy-loaded everything, the UX starts to feel janky. The goal is to balance speed with a smooth feel.

  • Don’t lazy load critical UI: Anything the user needs to see in the first 2 seconds should be right there in the initial bundle.
  • Use placeholders: If you’re lazy loading a big list, use skeleton screens so the layout doesn’t jump around when the data finally arrives.
  • Handle errors: Networks fail. If your dynamic import fails, make sure you show a “Try Again” button instead of just leaving a blank space.

Key Takeaways for LWC lazy loading

  • Use template if:true for basic conditional visibility.
  • Dynamic import() is your best friend for splitting large JavaScript files.
  • The IntersectionObserver API is perfect for components that sit “below the fold.”
  • Native loading="lazy" on images is a free performance win with zero effort.
  • Always prioritize the “First Contentful Paint” – keep the stuff the user sees first fast.

At the end of the day, LWC lazy loading is just about being respectful of your user’s time and their hardware. Start small by wrapping your heaviest child components in a conditional template and see how much faster your pages feel. You’ll notice the difference immediately, and your users definitely will too.

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