2nd/10_Wiki/Topics/Frontend/Client-Side Rendering (CSR).md

---
id: wiki-2026-0508-client-side-rendering-csr
title: Client-Side Rendering (CSR)
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [CSR, SPA Rendering]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [rendering, csr, spa, frontend, performance]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: TypeScript
  framework: React / Vue / Svelte
---

# Client-Side Rendering (CSR)

## 매 한 줄
> **"매 browser 가 매 HTML 을 그린다"**. CSR 은 server 가 빈 shell + JS bundle 만 보내고, browser 가 fetch + render 모두 수행 — 매 SPA 의 default mode, interactive app 에 강하나 매 first paint / SEO 매 weak.

## 매 핵심

### 매 lifecycle
1. Browser → server: `GET /` → minimal HTML + `<script src="bundle.js">`.
2. Browser parses HTML → fetches JS bundle.
3. JS executes → mounts framework → fetches data → renders DOM.
4. User interacts.

### 매 trade-off
| Pros | Cons |
|---|---|
| Rich interactivity | Slow TTI (특히 mobile) |
| Server cost low | SEO 매 needs hydration tricks |
| Client routing fast | Blank screen until JS loads |
| Offline-capable (PWA) | Bundle size matters a lot |

### 매 CSR vs SSR vs RSC (2026)
- CSR: dashboard, internal tool, app-like UX.
- SSR: marketing, blog, e-commerce.
- RSC: hybrid — server-render with client islands.
- SSG: docs, blog (rebuild on content change).

## 💻 패턴

### Vite + React CSR baseline
```tsx
// main.tsx
import { createRoot } from 'react-dom/client';
import App from './App';

createRoot(document.getElementById('root')!).render(<App />);
```
```html
<!-- index.html -->
<div id="root"></div>
<script type="module" src="/src/main.tsx"></script>
```

### Route-based code splitting
```tsx
import { lazy, Suspense } from 'react';
import { Routes, Route } from 'react-router';

const Dashboard = lazy(() => import('./Dashboard'));
const Settings = lazy(() => import('./Settings'));

export default function App() {
  return (
    <Suspense fallback={<Spinner />}>
      <Routes>
        <Route path="/dashboard" element={<Dashboard />} />
        <Route path="/settings" element={<Settings />} />
      </Routes>
    </Suspense>
  );
}
```

### Skeleton-first paint (perceived perf)
```tsx
function UsersList() {
  const { data, isLoading } = useQuery({ queryKey: ['users'], queryFn: fetchUsers });
  if (isLoading) return <UsersSkeleton rows={10} />;
  return <ul>{data!.map((u) => <li key={u.id}>{u.name}</li>)}</ul>;
}
```

### Pre-fetch on hover (link prefetch)
```tsx
<Link
  to="/dashboard"
  onMouseEnter={() => queryClient.prefetchQuery({ queryKey: ['dashboardData'], queryFn })}
>
  Dashboard
</Link>
```

### Service Worker for offline shell
```ts
// sw.ts
self.addEventListener('install', (e: any) => {
  e.waitUntil(caches.open('shell-v1').then((c) => c.addAll(['/', '/main.js', '/main.css'])));
});
self.addEventListener('fetch', (e: any) => {
  e.respondWith(caches.match(e.request).then((r) => r ?? fetch(e.request)));
});
```

### Bundle budget enforcement
```js
// vite.config.ts
export default {
  build: {
    rollupOptions: {
      output: {
        manualChunks: { vendor: ['react', 'react-dom'] },
      },
    },
    chunkSizeWarningLimit: 200, // KB
  },
};
```

### SEO via prerender (when CSR + needed)
```bash
# Use prerender for marketing routes only
npx prerender-spa-plugin --routes /,/about,/pricing
```

## 매 결정 기준
| 상황 | Render mode |
|---|---|
| Auth-walled dashboard | CSR |
| Marketing site | SSG or SSR |
| Mixed app (e-commerce) | RSC / SSR + islands |
| Rich realtime (Figma-like) | CSR + WebSocket |

**기본값**: 매 user-app (login wall 뒤) → CSR. 매 public content → SSR/SSG/RSC.

## 🔗 Graph
- 부모: [[Rendering-Strategies]] · [[프론트엔드_및_UIUX_표준|Frontend-Architecture]]
- 변형: [[React-Server-Components]]
- Adjacent: [[Core Web Vitals Optimization (INP, LCP 개선)|Core-Web-Vitals]] · [[Code-Splitting]] · [[Hydration]]

## 🤖 LLM 활용
**언제**: app-like UX, auth-protected, heavy client interactivity.
**언제 X**: 매 SEO-critical public page, low-end device 가 주 audience.

## ❌ 안티패턴
- **Mega-bundle**: 매 single chunk 5MB → split routes / vendor.
- **No skeleton / loading state**: 매 blank screen 매 perceived as broken.
- **CSR for blog/docs**: 매 SEO/perf 매 모두 lose — SSG choice.

## 🧪 검증 / 중복
- Verified (web.dev / React docs / Vite docs).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — CSR fundamentals + tradeoffs + patterns |