SSR vs CSR vs SSG: Complete Guide to Web Rendering Strategies

When building web applications, one of the most important decisions you'll make is how to render your content. Should the server generate HTML pages? Should the browser handle everything? Or maybe pre-generate everything at build time? This guide breaks down Server-Side Rendering (SSR), Client-Side Rendering (CSR), and Static Site Generation (SSG) in simple terms.

What is Web Rendering?

Rendering is the process of converting your code into HTML that browsers can display. Think of it like cooking - you can prepare meals in the kitchen (server), at the table (client), or meal prep everything in advance (static).

The Three Main Approaches

1. Server-Side Rendering (SSR) - Server cooks the meal fresh for each order
2. Client-Side Rendering (CSR) - Customer cooks their own meal at the table
3. Static Site Generation (SSG) - Meals are pre-cooked and served ready-to-eat

Server-Side Rendering (SSR)

SSR means the server generates complete HTML pages for each request. When a user visits your site, the server processes the request, runs your application code, and sends back a fully formed HTML page.

How SSR Works

1. User requests page → Server receives request
2. Server runs application code → Generates HTML
3. Server sends complete HTML → Browser displays page
4. Browser downloads JavaScript → Page becomes interactive

SSR Implementation Example

Here's how SSR works with Next.js:

// pages/products/[id].js - Next.js SSR
export async function getServerSideProps(context) {
  const { id } = context.params

  // This runs on the server for each request
  const product = await fetch(`https://api.example.com/products/${id}`).then(
    (res) => res.json(),
  )

  return {
    props: {
      product,
    },
  }
}

export default function ProductPage({ product }) {
  return (
    <div>
      <h1>{product.name}</h1>
      <p>{product.description}</p>
      <p>Price: ${product.price}</p>
    </div>
  )
}

SSR Pros and Cons

Advantages:

• Fast initial page load - Users see content immediately
• Great SEO - Search engines can easily crawl content
• Works without JavaScript - Content displays even if JS fails
• Better performance on slow devices - Less client-side processing

Disadvantages:

• Slower navigation - Each page request hits the server
• Higher server costs - Server does more work
• Complex caching - Dynamic content is harder to cache
• Server dependency - Needs server infrastructure

When to Use SSR

• E-commerce sites - Product pages need good SEO and fast loading
• News websites - Content changes frequently and needs to be searchable
• User dashboards - Personalized content that changes often
• Content-heavy sites - Blogs, documentation with lots of text

Client-Side Rendering (CSR)

CSR means the browser downloads a basic HTML shell and JavaScript code, then builds the page content using JavaScript. The "rendering" happens in the user's browser.

How CSR Works

1. User requests page → Server sends HTML shell + JavaScript
2. Browser downloads JavaScript → Runs application code
3. JavaScript fetches data → Updates page content
4. Page becomes fully interactive

CSR Implementation Example

Here's a typical CSR setup with React:

// App.js - Client-side React app
import React, { useState, useEffect } from 'react'

function ProductPage({ productId }) {
  const [product, setProduct] = useState(null)
  const [loading, setLoading] = useState(true)

  useEffect(() => {
    // This runs in the browser
    fetch(`https://api.example.com/products/${productId}`)
      .then((res) => res.json())
      .then((data) => {
        setProduct(data)
        setLoading(false)
      })
  }, [productId])

  if (loading) return <div>Loading...</div>

  return (
    <div>
      <h1>{product.name}</h1>
      <p>{product.description}</p>
      <p>Price: ${product.price}</p>
    </div>
  )
}

CSR Pros and Cons

Advantages:

• Fast navigation - No server requests after initial load
• Rich interactions - Smooth user experience like desktop apps
• Lower server costs - Server just serves static files
• Offline capability - Can work without internet connection

Disadvantages:

• Slow initial load - Must download JavaScript before showing content
• Poor SEO - Search engines struggle with JavaScript-heavy sites
• JavaScript dependency - Broken if JavaScript fails to load
• Performance issues - Slower on low-end devices

When to Use CSR

• Web applications - Tools, dashboards, admin panels
• Interactive sites - Games, calculators, complex user interfaces
• Private content - User-specific data that doesn't need SEO
• Progressive Web Apps - Apps that work offline

Static Site Generation (SSG)

SSG pre-generates all HTML pages at build time. Instead of creating pages when users request them, you build all pages once and serve them as static files.

How SSG Works

1. Build process runs → Generates all HTML pages
2. Pages deployed to CDN → Static files ready to serve
3. User requests page → CDN serves pre-built HTML instantly
4. Browser downloads JavaScript → Page becomes interactive

SSG Implementation Example

Here's SSG with Next.js:

// pages/products/[id].js - Next.js SSG
export async function getStaticPaths() {
  // Generate paths for all products at build time
  const products = await fetch('https://api.example.com/products').then((res) =>
    res.json(),
  )

  const paths = products.map((product) => ({
    params: { id: product.id.toString() },
  }))

  return {
    paths,
    fallback: false, // Show 404 for non-existent pages
  }
}

export async function getStaticProps({ params }) {
  // This runs at build time for each page
  const product = await fetch(
    `https://api.example.com/products/${params.id}`,
  ).then((res) => res.json())

  return {
    props: {
      product,
    },
    revalidate: 3600, // Regenerate page every hour
  }
}

export default function ProductPage({ product }) {
  return (
    <div>
      <h1>{product.name}</h1>
      <p>{product.description}</p>
      <p>Price: ${product.price}</p>
    </div>
  )
}

SSG Pros and Cons

Advantages:

• Extremely fast loading - Pre-built pages served instantly
• Excellent SEO - Search engines love static HTML
• High security - No server-side code execution
• Cheap hosting - Can use CDNs and static hosting

Disadvantages:

• Build time increases - More pages = longer builds
• Content updates require rebuilds - Can't change content without rebuilding
• Not suitable for dynamic content - User-specific content is challenging
• Complex for large sites - Thousands of pages can be difficult to manage

When to Use SSG

• Marketing websites - Landing pages, company websites
• Blogs and documentation - Content doesn't change frequently
• E-commerce catalogs - Product listings that update occasionally
• Portfolios - Personal websites showcasing work

Detailed Comparison

Performance Comparison

Aspect	SSR	CSR	SSG
First Contentful Paint	Fast ⚡	Slow 🐌	Fastest ⚡⚡
Time to Interactive	Medium 🟡	Slow 🐌	Fast ⚡
Navigation Speed	Slow 🐌	Fast ⚡	Fast ⚡
Bundle Size Impact	Low 📦	High 📦📦	Low 📦

SEO and Crawling

// SSR/SSG - Search engines see this:
<html>
  <head><title>Amazing Product - Best Price</title></head>
  <body>
    <h1>Amazing Product</h1>
    <p>This product is amazing because...</p>
  </body>
</html>

// CSR - Search engines might see this:
<html>
  <head><title>Loading...</title></head>
  <body>
    <div id="root"><!-- Content loads via JavaScript --></div>
    <script src="app.js"></script>
  </body>
</html>

Development Complexity

SSR Complexity:

• Server configuration required
• Hydration issues - client and server must match
• Environment differences (server vs browser)
• Caching strategies needed

CSR Complexity:

• Simple setup and deployment
• Client-side routing
• State management for data fetching
• Loading states and error handling

SSG Complexity:

• Build-time data fetching
• Incremental Static Regeneration (ISR) for updates
• Dynamic routing setup
• Content management integration

Hybrid Approaches

Modern frameworks let you mix different rendering strategies:

Next.js Hybrid Example

// pages/index.js - SSG for homepage
export async function getStaticProps() {
  return { props: { posts: await getBlogPosts() } }
}

// pages/dashboard.js - CSR for user dashboard
export default function Dashboard() {
  const { data } = useSWR('/api/user', fetcher)
  return <div>{data?.name}'s Dashboard</div>
}

// pages/product/[id].js - SSR for product pages
export async function getServerSideProps({ params }) {
  return { props: { product: await getProduct(params.id) } }
}

Progressive Enhancement

Start with SSG/SSR for content, then enhance with JavaScript:

// Base HTML works without JavaScript
function ProductPage({ product, reviews }) {
  const [showAllReviews, setShowAllReviews] = useState(false)

  return (
    <div>
      {/* This content renders on server */}
      <h1>{product.name}</h1>
      <p>{product.description}</p>

      {/* This enhances with JavaScript */}
      <div>
        {reviews.slice(0, showAllReviews ? reviews.length : 3).map((review) => (
          <div key={review.id}>{review.text}</div>
        ))}
        <button onClick={() => setShowAllReviews(!showAllReviews)}>
          {showAllReviews ? 'Show Less' : 'Show All'} Reviews
        </button>
      </div>
    </div>
  )
}

Implementation Best Practices

SSR Best Practices

1. Implement Proper Caching

// Express.js caching example
app.get('/product/:id', cache('5 minutes'), async (req, res) => {
  const product = await getProduct(req.params.id)
  res.render('product', { product })
})

2. Handle Loading States

// Show loading UI while server processes
function ProductPage({ product, loading }) {
  if (loading) return <ProductSkeleton />
  return <ProductDetails product={product} />
}

3. Optimize Critical CSS

<!-- Inline critical CSS for faster rendering -->
<style>
  .header {
    background: #333;
    color: white;
  }
  .main-content {
    max-width: 1200px;
    margin: 0 auto;
  }
</style>

CSR Best Practices

1. Implement Smart Loading

// Show skeleton while loading
function ProductList() {
  const { data: products, loading } = useProducts()

  if (loading) return <ProductListSkeleton />

  return (
    <div>
      {products.map((product) => (
        <ProductCard key={product.id} product={product} />
      ))}
    </div>
  )
}

2. Code Splitting

// Load components only when needed
const Dashboard = lazy(() => import('./Dashboard'))
const Profile = lazy(() => import('./Profile'))

function App() {
  return (
    <Suspense fallback={<Loading />}>
      <Routes>
        <Route path="/dashboard" element={<Dashboard />} />
        <Route path="/profile" element={<Profile />} />
      </Routes>
    </Suspense>
  )
}

3. Preload Critical Data

// Preload data for better UX
function App() {
  useEffect(() => {
    // Preload user data
    queryClient.prefetchQuery('user', fetchUser)
  }, [])

  return <Router />
}

SSG Best Practices

1. Incremental Static Regeneration

// Update static pages without full rebuild
export async function getStaticProps({ params }) {
  const product = await getProduct(params.id)

  return {
    props: { product },
    revalidate: 60, // Regenerate every minute if needed
  }
}

2. Fallback Pages

// Handle new pages gracefully
export async function getStaticPaths() {
  const popularProducts = await getPopularProducts()

  return {
    paths: popularProducts.map((p) => ({ params: { id: p.id } })),
    fallback: 'blocking', // Generate other pages on-demand
  }
}

3. Build Optimization

// Only regenerate changed pages
export async function getStaticProps({ params }) {
  const product = await getProduct(params.id, {
    lastModified: process.env.LAST_BUILD_TIME,
  })

  // Skip if not modified
  if (!product.modified) {
    return { notFound: true }
  }

  return { props: { product } }
}

Common Issues and Solutions

Hydration Mismatches (SSR)

Problem: Client and server render different content

// Bad - causes hydration mismatch
function TimeComponent() {
  return <div>Current time: {new Date().toLocaleString()}</div>
}

// Good - ensure server and client match
function TimeComponent() {
  const [time, setTime] = useState(null)

  useEffect(() => {
    setTime(new Date().toLocaleString())
  }, [])

  return <div>Current time: {time || 'Loading...'}</div>
}

SEO Issues (CSR)

Problem: Search engines can't see JavaScript-rendered content

Solution: Use Server-Side Rendering or Prerendering

// Add prerendering for CSR apps
// prerender.config.js
module.exports = {
  routes: [
    '/',
    '/products',
    '/about',
    // Add routes that need SEO
  ],
  renderer: '@prerenderer/renderer-puppeteer',
}

Build Time Issues (SSG)

Problem: Too many pages causing slow builds

Solutions:

// 1. Use fallback pages
export async function getStaticPaths() {
  return {
    paths: [], // Generate no pages at build time
    fallback: 'blocking', // Generate on first request
  }
}

// 2. Prioritize important pages
export async function getStaticPaths() {
  const importantProducts = await getImportantProducts()

  return {
    paths: importantProducts.map((p) => ({ params: { id: p.id } })),
    fallback: true, // Generate others as needed
  }
}

Performance Monitoring

Key Metrics to Track

Core Web Vitals:

• Largest Contentful Paint (LCP) - Loading performance
• First Input Delay (FID) - Interactivity
• Cumulative Layout Shift (CLS) - Visual stability

Monitoring Implementation

// Track performance metrics
function trackWebVitals() {
  import('web-vitals').then(({ getCLS, getFID, getLCP }) => {
    getCLS(console.log)
    getFID(console.log)
    getLCP(console.log)
  })
}

// Track in Next.js
export function reportWebVitals(metric) {
  // Send to analytics
  analytics.track(metric.name, {
    value: metric.value,
    page: window.location.pathname,
  })
}

Decision Framework

Choose SSR When:

• ✅ You need excellent SEO
• ✅ Content changes frequently
• ✅ Fast initial page load is critical
• ✅ You have server infrastructure
• ✅ Content is personalized

Choose CSR When:

• ✅ Building an interactive web app
• ✅ SEO is not important
• ✅ Users spend lots of time on site
• ✅ You want to minimize server costs
• ✅ Offline functionality is needed

Choose SSG When:

• ✅ Content doesn't change often
• ✅ You need the fastest possible loading
• ✅ SEO is important
• ✅ You want minimal hosting costs
• ✅ Security is a priority

Decision Tree

Does your content change frequently?
├── Yes → Do you need SEO?
│   ├── Yes → Use SSR
│   └── No → Use CSR
└── No → Do you need SEO?
    ├── Yes → Use SSG
    └── No → Use CSR or SSG

Framework Recommendations

Next.js (React)

• Best for: Full-stack React applications
• Supports: SSR, CSR, SSG, ISR (hybrid)
• Ideal when: You want flexibility to use different strategies

Nuxt.js (Vue)

• Best for: Vue.js applications
• Supports: SSR, CSR, SSG
• Ideal when: You're using Vue ecosystem

Gatsby (React)

• Best for: Static sites with rich content
• Supports: SSG with hydration
• Ideal when: Building content-heavy sites

SvelteKit (Svelte)

• Best for: Performance-focused applications
• Supports: SSR, CSR, SSG
• Ideal when: Bundle size and performance are critical

Conclusion

Understanding SSR, CSR, and SSG helps you make better decisions for your web applications. Each approach has its place:

• SSR gives you dynamic content with good SEO
• CSR provides rich interactivity with simple deployment
• SSG delivers maximum performance for static content

Key Takeaways:

1. Consider your content - Static vs dynamic determines your options
2. Think about your users - Fast loading vs rich interactions
3. Evaluate your resources - Server costs vs build complexity
4. Plan for SEO - Search visibility requirements
5. Start simple - You can always add complexity later

Modern frameworks make it easy to combine approaches, so you don't have to choose just one. Start with the approach that fits your main use case, then optimize specific pages as needed.

The best rendering strategy is the one that serves your users' needs while fitting your technical constraints and business goals.

References

• Next.js Rendering Documentation
• Web.dev Rendering Patterns
• React Server Components
• Core Web Vitals
• Nuxt.js Rendering Modes
• Gatsby Static Generation
• SvelteKit Rendering
• Hydration Explained