Lazy Loading Like a Pro: Angular’s Secrets to Blazing Performance

This content originally appeared on DEV Community and was authored by Karol Modelski

Waiting for an Angular app to load can be frustrating. Lazy loading speeds things up by loading only the essentials first, then loading other parts as needed. It’s an easy way to make your app feel fast and responsive using Angular’s router.

You can also preload some parts in the background for smoothness, but be careful with module setup to avoid issues like duplicated services or routing errors. Mastering these will help you build efficient Angular apps users love.

Understanding Lazy Loading in Angular

Think of your Angular app as a busy city. Loading everything at once causes traffic jams. Lazy loading opens roads and buildings only when needed, making your app faster and smoother. This chapter covers how Angular loads parts of your app on demand.

What is Lazy Loading?

Lazy loading breaks your app into smaller chunks and loads them only when the user visits a specific route. This speeds up initial loading and improves user experience by avoiding unnecessary data loading.

Key Takeaway 1: Lazy loading limits what the app loads upfront to boost speed.
Key Takeaway 2: Angular’s router controls what and when to load.

Module-Based Lazy Loading

Modules are like neighborhoods in your app. Angular loads each neighborhood only when you visit it using loadChildren.

Example:

const routes: Routes = [
  {
    path: 'admin',
    loadChildren: () => import('./admin/admin.module').then(m => m.AdminModule)
  }
];

Key Takeaway 1: loadChildren lazily loads full modules on demand.
Key Takeaway 2: This cuts down the initial bundle size and speeds up startup

Component-Based Lazy Loading

Want to load just one building? Use loadComponent to lazy load standalone components on the fly.

Example:

const routes: Routes = [
  {
    path: 'profile',
    loadComponent: () => import('./profile/profile.component').then(c => c.ProfileComponent)
  }
];

Key Takeaway 1: loadComponent loads individual components lazily.
Key Takeaway 2: Keeps your app lightweight and focused.

Lazy loading helps keep Angular apps fast by loading modules or components only when needed. Using loadChildren and loadComponent makes your app more efficient and user-friendly.

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Lazy Loading in Angular: Modular vs Standalone Architecture Simplified

Lazy loading in Angular means loading parts of your app only when needed, making your app faster and lighter. This chapter covers two ways to do it: the classic modular approach and the modern standalone component approach.

Modular Lazy Loading

Feature modules are like themed rooms in your app. Angular loads a module only when you visit its route.

Generate a feature module with:

ng generate module feature-name --route feature-path --module app.module

Configure routes with loadChildren:

const routes: Routes = [
  {
    path: 'feature-path',
    loadChildren: () =>
      import('./feature-name/feature-name.module').then(m => m.FeatureNameModule)
  }
];

Key Takeaway: Modules keep your app organized and load only what’s necessary.

Standalone Lazy Loading

Standalone components drop the need for modules. Each component declares itself with standalone: true.

Declare a standalone component:

@Component({
  selector: 'app-feature',
  standalone: true,
  templateUrl: './feature.component.html',
  imports: [CommonModule]
})
export class FeatureComponent {}

Lazy load with loadComponent:

const routes: Routes = [
  {
    path: 'feature-path',
    loadComponent: () =>
      import('./feature/feature.component').then(m => m.FeatureComponent)
  }
];

Key Takeaway: Standalone components simplify lazy loading with less boilerplate.

Which to Choose?

Key Takeaway: Modular suits big projects; standalone fits modern, simple apps.

Both ways help lazy loading in Angular, making apps faster and cleaner. Pick modular for traditional setups or standalone for a fresh, simple approach.

Unlocking Angular Lazy Loading — Modular & Standalone Approaches

Think of your Angular app as a city — loading only the streets your visitors walk on first. That’s lazy loading! This chapter guides you through smart lazy loading in both the classic NgModule setup and Angular’s new standalone component architecture, including the latest Angular 18 @defer feature.

Lazy Loading in Traditional Modules

In classic Angular, loadChildren lazy loads modules on demand, keeping your app startup quick. Want more control? Use custom preloading to load select modules early without slowing down the initial load:

export class SmartPreloader implements PreloadingStrategy {
  preload(route: Route, load: () => Observable<any>): Observable<any> {
    return route.data?.preload ? load() : of(null);
  }
}

This balances speed and readiness by choosing what to preload.

Lazy Loading with Standalone Components

Standalone components let you lazy load directly with loadComponent—no modules needed! This shrinks your initial bundle and simplifies routing:

export const routes = [
  { path: 'dashboard', loadComponent: () => import('./dashboard.component').then(m => m.DashboardComponent) }
];

Pair this with preloading for a smooth, fast user experience.

Angular 18’s `@defer` Block for Template Lazy Loading

The @defer block lets you load heavy UI parts only when needed, showing lightweight placeholders meanwhile:

@defer {
  <app-heavy-widget [data]="data$ | async"></app-heavy-widget>
}
@placeholder {
  <p>Loading widget...</p>
}

This improves perceived speed and keeps your app responsive.

Lazy loading — whether via modules or standalones, enhanced by Angular 18’s @defer—is your key to faster, better Angular apps. Mix these tools to fit your app’s unique needs and delight users with speed.

Best Practices and Performance Tips for Lazy Loading in Angular Modular and Standalone Architectures

Lazy loading speeds up your Angular app by loading code only when needed. Whether you use the classic modular approach or modern standalone components, mastering lazy loading ensures your app is fast and easy to maintain.

Avoid Eager Imports of Lazy Code

Lazy-loaded modules or components must not be imported directly in the main app or shared modules. Instead:

Use loadChildren to lazy load modules.
Use loadComponent to lazy load standalone components.

This keeps your initial bundle light and improves load times.

Keep Lazy Modules and Standalone Components Self-Contained

Lazy code should be independent:

Feature modules declare their own components, services, and pipes.
Standalone components list dependencies in their imports array.

Keep shared code in dedicated shared modules or libraries to avoid duplication.

Manage Dependencies Wisely

Only include necessary dependencies in lazy modules/components:

Break up large shared modules.
Use providedIn: 'root' for shared services, or provide services locally inside lazy standalone components.

This reduces size and improves performance.

Code Examples: Modular vs Standalone Lazy Loading

Modular lazy loading:

const routes: Routes = [
  { path: 'feature', loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule) }
];

Standalone lazy loading:

const routes: Routes = [
  { path: 'feature', loadComponent: () => import('./feature/feature.component').then(m => m.FeatureComponent) }
];

Standalone component example:

@Component({
  standalone: true,
  imports: [CommonModule],
  providers: [FeatureService],
  templateUrl: './feature.component.html',
})
export class FeatureComponent {
  private service = inject(FeatureService);
}

Avoid eager imports, keep lazy code self-contained, and manage dependencies carefully to maximize lazy loading benefits — whether in modular or standalone Angular apps. These best practices help keep apps fast and maintainable.

Conclusion

Lazy loading transforms Angular apps by loading only what’s necessary when it’s needed, greatly boosting performance and user experience. We’ve covered how to implement it in feature modules and explore advanced strategies like preloading and defer blocks.

Now, it’s time to audit your app, find lazy loading opportunities, and take advantage of these powerful techniques. For further learning, check out the official Angular docs and tutorials below.

Thanks for Reading

I hope these tips help you ship better, faster, and more maintainable frontend projects.

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