---
id: wiki-2026-0508-웹-프론트엔드-성능-최적화
title: 웹 프론트엔드 성능 최적화
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Frontend performance, Web perf, Core Web Vitals]
duplicate_of: none
source_trust_level: A
confidence_score: 0.95
verification_status: applied
tags: [performance, frontend, core-web-vitals, optimization]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: TypeScript
  framework: Next.js / Vite
---

# 웹 프론트엔드 성능 최적화

## 매 한 줄
> **"매 LCP/INP/CLS 의 3 metric 을 따라 image, JS, layout 을 deliberate optimize"**. 2026 매 INP (Interaction to Next Paint) 가 FID 대체 → 매 long task 의 적극 splitting. 매 RUM 으로 매 측정, lab data 의 보완.

## 매 핵심

### 매 Core Web Vitals (2026)
- **LCP (Largest Contentful Paint)**: ≤ 2.5s — 매 hero image/text 의 render 시간.
- **INP (Interaction to Next Paint)**: ≤ 200ms — 매 user interaction 의 response.
- **CLS (Cumulative Layout Shift)**: ≤ 0.1 — 매 layout 안정성.

### 매 optimization layer
1. **Network**: HTTP/3, CDN, preload, prefetch, brotli.
2. **JS**: code splitting, tree shake, defer, async, lazy import.
3. **CSS**: critical CSS inline, remove unused, contain.
4. **Image**: AVIF/WebP, responsive srcset, lazy, dimension hints.
5. **Render**: Server Components, streaming SSR, partial hydration.

### 매 응용
1. Next.js App Router 매 RSC + streaming.
2. Astro 매 island architecture.
3. Image CDN (Cloudinary, Cloudflare Images) 매 auto format/size.

## 💻 패턴

### Image — 매 next/image
```tsx
import Image from 'next/image';

<Image
  src="/hero.jpg"
  alt="Hero"
  width={1600}
  height={900}
  priority // 매 above-fold
  sizes="(max-width: 768px) 100vw, 80vw"
  placeholder="blur"
  blurDataURL="data:image/jpeg;base64,..."
/>
```

### Code splitting — 매 dynamic import
```typescript
// 매 route-level: Next.js 자동
// 매 component-level: dynamic
import dynamic from 'next/dynamic';

const HeavyChart = dynamic(() => import('./HeavyChart'), {
  loading: () => <Skeleton />,
  ssr: false, // 매 client-only
});
```

### LCP — 매 preload critical
```html
<link rel="preload" as="image" href="/hero.avif"
  imagesrcset="/hero-mobile.avif 480w, /hero.avif 1600w"
  imagesizes="100vw" fetchpriority="high">

<link rel="preconnect" href="https://cdn.example.com" crossorigin>
<link rel="dns-prefetch" href="https://analytics.example.com">
```

### INP — 매 long task splitting
```typescript
async function processLargeList(items: Item[]) {
  for (const [i, item] of items.entries()) {
    process(item);
    if (i % 50 === 0) {
      await new Promise((r) => setTimeout(r, 0)); // 매 yield
    }
  }
}

// 매 또는 scheduler API
import { scheduler } from 'scheduler';
await scheduler.yield();
```

### CLS — 매 dimension reserve
```css
/* 매 aspect-ratio */
.thumb {
  aspect-ratio: 16 / 9;
  width: 100%;
  background: #eee;
}

/* 매 font-display: optional → CLS 0 */
@font-face {
  font-family: 'Inter';
  src: url('/inter.woff2') format('woff2');
  font-display: optional; /* 매 swap 매 layout shift, optional 매 안정 */
}
```

### Server Components — 매 zero-JS by default
```tsx
// app/products/page.tsx — Server Component
async function ProductsPage() {
  const products = await db.products.findAll();
  return (
    <ul>
      {products.map((p) => <ProductCard key={p.id} {...p} />)}
    </ul>
  );
}
// 매 client component 만 JS 의 hydrate
```

### RUM — 매 web-vitals 수집
```typescript
import { onLCP, onINP, onCLS } from 'web-vitals';

function send(metric) {
  navigator.sendBeacon('/rum',
    JSON.stringify({ name: metric.name, value: metric.value, id: metric.id })
  );
}

onLCP(send);
onINP(send);
onCLS(send);
```

### Critical CSS — 매 inline
```html
<head>
<style>
  /* 매 above-fold critical CSS — beasties/critters 등으로 추출 */
  body { margin: 0; font-family: system-ui; }
  .header { background: #fff; height: 64px; }
</style>
<link rel="preload" href="/main.css" as="style" onload="this.rel='stylesheet'">
</head>
```

### Service Worker — 매 stale-while-revalidate
```javascript
// sw.js
self.addEventListener('fetch', (e) => {
  if (e.request.destination === 'image') {
    e.respondWith((async () => {
      const cache = await caches.open('img-v1');
      const cached = await cache.match(e.request);
      const networked = fetch(e.request).then((res) => {
        cache.put(e.request, res.clone()); return res;
      });
      return cached || networked;
    })());
  }
});
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| 매 hero image | priority + preload + AVIF |
| 매 below-fold widget | dynamic import + ssr:false |
| 매 long table | virtualization (react-window) |
| 매 large list iteration | scheduler.yield |
| 매 third-party script | next/script with strategy |

**기본값**: RSC + next/image + dynamic + Web Vitals RUM.

## 🔗 Graph
- 부모: [[Web Performance]] · [[Frontend Architecture]]
- 변형: [[INP Optimization]] · [[LCP Optimization]] · [[CLS]]
- 응용: [[Next.js]] · [[Astro]] · [[Remix]]
- Adjacent: [[Lighthouse]] · [[Web Vitals]]

## 🤖 LLM 활용
**언제**: 매 perf audit (Lighthouse JSON 분석), 매 bundle size review, 매 RUM data triage.
**언제 X**: 매 actual measurement (lab/RUM 도구 가 더 정확).

## ❌ 안티패턴
- **모든 component client**: 매 RSC 무시 매 JS bundle 폭발.
- **lazy load hero image**: 매 LCP 악화.
- **fixed-pixel layout**: 매 mobile 매 CLS.
- **synchronous third-party**: 매 main thread block.

## 🧪 검증 / 중복
- Verified (web.dev, Next.js docs, Chrome DevRel).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — Core Web Vitals (LCP/INP/CLS), RSC, RUM 패턴 정리 |
