NgOptimizedImage (REQUIRED for images)
import { NgOptimizedImage } from '@angular/common';
@Component({
imports: [NgOptimizedImage],
template: `
<!-- LCP image: add priority -->
<img ngSrc="hero.jpg" width="800" height="400" priority>
<!-- Regular: lazy loaded by default -->
<img ngSrc="thumb.jpg" width="200" height="200">
<!-- Fill mode (parent needs position: relative) -->
<img ngSrc="bg.jpg" fill>
<!-- With placeholder -->
<img ngSrc="photo.jpg" width="400" height="300" placeholder>
`
})
Rules
- ALWAYS set
width and height (or fill)
- Add
priority to LCP (Largest Contentful Paint) image
- Use
ngSrc not src
- Parent of
fill image must have position: relative/fixed/absolute
@defer - Lazy Components
@defer (on viewport) {
<heavy-component />
} @placeholder {
<p>Placeholder shown immediately</p>
} @loading (minimum 200ms) {
<spinner />
} @error {
<p>Failed to load</p>
}
Triggers
| Trigger | When to Use |
|---|
on viewport | Below the fold content |
on interaction | Load on click/focus/hover |
on idle | Load when browser is idle |
on timer(500ms) | Load after delay |
when condition | Load when expression is true |
<!-- Multiple triggers -->
@defer (on viewport; on interaction) {
<comments />
}
<!-- Conditional -->
@defer (when showComments()) {
<comments />
}
Lazy Routes
// Single component
{
path: 'admin',
loadComponent: () => import('./features/admin/admin').then(c => c.AdminComponent)
}
// Feature with child routes
{
path: 'users',
loadChildren: () => import('./features/users/routes').then(m => m.USERS_ROUTES)
}
SSR & Hydration
bootstrapApplication(AppComponent, {
providers: [
provideClientHydration()
]
});
| Scenario | Use |
|---|
| SEO critical (blog, e-commerce) | SSR |
| Dashboard/Admin | CSR |
| Static marketing site | SSG/Prerender |
Slow Computations
| Solution | When |
|---|
| Optimize algorithm | First choice always |
| Pure pipes | Cache single result |
| Memoization | Cache multiple results |
computed() | Derived signal state |
NEVER trigger reflows/repaints in lifecycle hooks (ngOnInit, ngAfterViewInit).
Resources
