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Lazy Loading & Preloading Strategies

Optimize Angular bundle size with lazy loading.

Lazy Loading​

Feature modules are loaded on demand:

const routes: Routes = [
  {
    path: "tasks",
    loadChildren: () =>
      import("./tasks/tasks.module").then((m) => m.TasksModule),
  },
  {
    path: "employees",
    loadChildren: () =>
      import("./employees/employees.module").then((m) => m.EmployeesModule),
  },
];

Preloading Strategies​

PreloadAllModules​

Preloads all lazy modules after the app loads:

@NgModule({
  imports: [
    RouterModule.forRoot(routes, {
      preloadingStrategy: PreloadAllModules
    })
  ]
})

Custom Preloading​

Preload only modules the user is likely to visit:

@Injectable()
export class SelectivePreloadingStrategy implements PreloadingStrategy {
  preload(route: Route, load: () => Observable<any>): Observable<any> {
    return route.data?.["preload"] ? load() : of(null);
  }
}

Bundle Analysis​

# Analyze bundle sizes
yarn build --stats-json
npx webpack-bundle-analyzer dist/stats.json

Tips​

  • Keep feature modules independent
  • Use SharedModule for common components
  • Avoid importing large libraries in CoreModule
  • Use dynamic imports for heavy components