---
name: angular-performance-e579c0d8ac36
description: >
  Angular performance: NgOptimizedImage, @defer, lazy loading, SSR.
  Trigger: When optimizing Angular app performance, images, or lazy loading.
metadata:
  author: gentleman-programming
  version: "1.0"
---

## NgOptimizedImage (REQUIRED for images)

```typescript
import { NgOptimizedImage } from '@angular/common';

@Component({
  imports: [NgOptimizedImage],
  template: `
    <!-- inline for docs brevity; use templateUrl in production -->
    <!-- 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

```html
@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 |

```html
<!-- Multiple triggers -->
@defer (on viewport; on interaction) {
  <comments />
}

<!-- Conditional -->
@defer (when showComments()) {
  <comments />
}
```

---

## Lazy Routes

```typescript
// 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

```typescript
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

- https://angular.dev/guide/image-optimization
- https://angular.dev/guide/defer
- https://angular.dev/best-practices/runtime-performance
- https://angular.dev/guide/ssr


---
Source attribution: CamiloAndresGTRUniandes
Original project: https://github.com/CamiloAndresGTRUniandes/lucy-ai/blob/52e3d6d9faf7773a4a764475b8f5a92a72e39749/skills/angular-performance/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Dave AI.

## Upstream license notice

MIT License

Copyright (c) 2026 Camilo Andres / lucy-ai

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Dave AI resource metadata

Creator / publisher: CamiloAndresGTRUniandes
Original project: https://github.com/CamiloAndresGTRUniandes/lucy-ai/blob/52e3d6d9faf7773a4a764475b8f5a92a72e39749/skills/angular-performance/SKILL.md
Attribution basis: Source repository record

Fields of work: Design, Development & Engineering
Roles: Frontend Developer, Full-Stack Developer, UX Designer
Specialties: Cross Platform, Frontend
Tools: Angular
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: b22e6fde5dfaabf980127732195290b026eb42ea5628ce178ca16931ac1ba613