Server-Side Rendering vs Static Site Generation: A Beginner’s Guide

Choosing how your web pages are rendered is a crucial decision in web development. This guide will break down the concepts of Server-Side Rendering (SSR) and Static Site Generation (SSG), comparing their performance, SEO impact, and developer experience. Beginners and web developers alike will find valuable insights into selecting the right rendering method for their projects.

Understanding SSR and SSG

High-Level Definitions

• Server-Side Rendering (SSR): In SSR, pages are rendered on the server when requested by a user. The server fetches the necessary data, generates the HTML, and sends it to the browser, which can then display content immediately. If a client framework like React or Vue is used, JavaScript will hydrate the HTML later to add interactivity.

• Static Site Generation (SSG): SSG involves rendering pages ahead of time (usually at build time) into static HTML files, which are deployed to a CDN or static host. These files are served directly to users, eliminating rendering time during requests.

How They Differ from Client-Side Rendering (CSR)

• Client-Side Rendering (CSR): In CSR, the server sends an empty HTML shell, and the browser uses JavaScript to build the UI. CSR is flexible and great for single-page applications but can result in slower initial load times and pose challenges for crawlers unless pre-rendering is implemented.

Key Terms

• Pre-rendering: Generating HTML ahead of time (SSG) or on-demand (SSR).
• Hydration: Attaching event listeners to static HTML to make it interactive.
• Dynamic Rendering: Combining server-side and client-side rendering based on user or route.

For practical examples, see Next.js’s official explanation of pre-rendering.

How SSR Works: A Simple Flow and Example

Typical SSR Request-Response Flow

1. The browser requests a URL (e.g., /products/123).
2. The server receives this request.
3. The server fetches the necessary data and renders the HTML for that route.
4. The server sends the rendered HTML back to the client.
5. The browser displays the HTML immediately. If a JavaScript framework is used, it will subsequently hydrate the page to add interactivity.

Advantages of SSR

• Fresh content is delivered with each request.
• Excellent for SEO since crawlers see fully-rendered HTML.
• Suitable for personalized content, such as user dashboards.

Drawbacks of SSR

• Higher server resource usage (CPU/memory) per request leads to increased operational costs.
• Potentially higher latency if the server or APIs are slow.

Conceptual SSR Code (Node/Express Example)

// conceptual example, not production-ready
const express = require('express');
const app = express();

app.get('/product/:id', async (req, res) => {
  const id = req.params.id;
  const product = await fetchProductFromAPI(id);
  const html = renderProductPageToHtml(product);
  res.set('Content-Type', 'text/html');
  res.send(html);
});

app.listen(3000);

Next.js SSR Example (Simplified)

// pages/product/[id].js
export async function getServerSideProps(context) {
  const { id } = context.params;
  const product = await fetch(`https://api.example.com/products/${id}`).then(r => r.json());
  return { props: { product } };
}

export default function ProductPage({ product }) {
  return <div>{product.name}</div>;
}

How SSG Works: A Simple Flow and Example

Build-Time Flow for SSG

1. At build time, your static site generator runs its scripts.
2. The generator fetches data and creates static HTML files for each page.
3. The generated files are deployed to a CDN or static host.
4. When requested, the CDN serves the static HTML quickly.

Example: Generating a Blog at Build Time

• Data Source: Markdown files or a headless CMS.
• Build Step: Read all posts, create an HTML file for each post, write files to /out.

Simple Conceptual Build Script (Node.js Pseudo-Code)

const posts = loadAllMarkdown('posts');
posts.forEach(post => {
  const html = renderPostToHtml(post);
  fs.writeFileSync(`out/posts/${post.slug}.html`, html);
});
// Deploy `out/` to a CDN/static host

Advantages of SSG

• Fast delivery from a CDN equals low latency and quick Time to First Byte (TTFB).
• Cost-effective hosting options (S3, Netlify, Vercel, GitHub Pages).
• High performance during traffic spikes due to static nature.

Limitations of SSG

• Content freshness depends on the last build—frequent updates require frequent builds.
• Not ideal for user-specific content (e.g., dashboards).

Learn more about SSG principles at JAMstack.

SSR vs. SSG: Features, Pros, and Cons

Comparison Table

When Each Approach Shines

• SSG is ideal for marketing sites, documentation, blogs, and product pages with infrequent content changes.
• SSR is best for user-specific pages, real-time updates, or personalized content.
• Ecommerce product pages can benefit from both: SSG for page rendering combined with serverless endpoints for dynamic content.

Hybrid and Middle-Ground Solutions

Modern frameworks enable hybrid models:

• Incremental Static Regeneration (ISR): Rebuild specific pages in the background to update CDN content. For more details, check out Next.js docs.
• On-demand revalidation: Trigger a rebuild of a page upon data changes, using webhooks.
• Edge/Serverless SSR: Render at the CDN edge for reduced latency.

These options allow you to maximize the advantages of SSG while maintaining near-real-time freshness.

Performance, Caching, and CDN Considerations

CDN and Cache Basics

• For SSG: CDNs cache static assets at edge locations, providing rapid delivery.
• For SSR: Use CDNs to cache entire responses or implement advanced caching strategies.

HTTP Caching Headers Example

# For static HTML files (SSG), long TTL
Cache-Control: public, max-age=31536000, immutable

# For SSR responses with acceptable short freshness
Cache-Control: public, max-age=60, stale-while-revalidate=30

Stale-While-Revalidate

This method allows clients to serve stale responses while refreshing content in the background, ideal for near-real-time updates without perceived delays.

Caching Strategies for SSR

Utilize reverse proxies or edge CDNs that support dynamic response caching. Cache API responses on the server to reduce calls—see our Redis caching patterns guide.

Edge Rendering and Serverless

Edge SSR minimizes geographic latency with complex implications (cold starts, debugging). Serverless functions provide on-demand SSR, but be mindful of cold starts and scalability issues.

Tools for Measuring Performance

• Lighthouse: Built into Chrome DevTools to audit key performance metrics.
• WebPageTest: Offers detailed metrics and network emulation capabilities: WebPageTest.
• Use curl to examine HTTP headers: curl -I https://example.com/page.

SEO, Metadata, and Social Previews

Benefits of Pre-Rendered HTML

Search engines prefer pre-rendered HTML for indexing and link previews. SSR or SSG delivers reliable and fast results compared to CSR.

Meta Tags and Open Graph

• With SSG: Meta tags are generated during the build for predictable pages.
• With SSR: Meta tags can be generated dynamically, aiding personalized previews.

Structured Data and Sitemaps

• SSG allows sitemap generation at build time, while larger sites benefit from SSR for dynamic sitemaps.
• Always include structured data (JSON-LD) where relevant to enhance rich search results. For more, refer to Google’s rendering guide.

When to Choose SSR, SSG, or a Hybrid

Decision Checklist

1. Frequency of content changes: SSG for static content; SSR for real-time updates.
2. Personalization needs: SSR for user-specific data.
3. Traffic patterns: SSG/CDN for unpredictable spikes.
4. Hosting budget: SSG is typically cheaper at scale.
5. Developer familiarity: Long build times may push towards SSR.

Short Scenario Recommendations

• Marketing pages, documentation, blogs: SSG.
• News sites with rapid updates: SSG with incremental builds or SSR for latest news.
• User dashboards and checkout flows: SSR or hybrid SPA with SSR for SEO.

Start with SSG for content-driven sites, transitioning specific routes to SSR as needs arise. Explore the Next.js pre-rendering docs for more options.

Migration Tips & Best Practices

Migrating SSG -> SSR

1. Identify dynamic routes requiring SSR for freshness or personalization.
2. Create API endpoints for SSR handler calls.
3. Implement SSR for necessary routes.
4. Utilize caching strategies to optimize performance.
5. Monitor and iterate based on performance metrics.

Migrating SSR -> SSG

1. Identify static pages suitable for SSG.
2. Replace server-rendered templates with build-time generation.
3. Use incremental generation if full rebuilds are costly.

Testing and Monitoring

• Measure performance with Lighthouse and WebPageTest for TTFB, FCP, TTI.
• Monitor server metrics if using SSR, and configure autoscaling.
• Implement tracing and APM for SSR endpoints.

Common Pitfalls

• Rendering unnecessary routes on the server increases costs.
• Failing to set caching headers properly complicates SSR performance.
• Allowing long SSG build times without adopting incremental strategies. Large repositories benefit from build caching strategies; read our monorepo vs multi-repo guide for CI/CD insights.

Common Misconceptions and FAQs

Q: Is SSG always faster than SSR?
A: Not necessarily. SSG served from a CDN is generally quicker for static content, but SSR can compete with proper caching and edge rendering. Testing is essential for your specific needs.

Q: Does SSR eliminate the need for JavaScript?
A: No. SSR provides HTML initially; for interactivity with frameworks like React, JavaScript will hydrate the page.

Q: Can I mix SSR and SSG on the same site?
A: Yes! Frameworks like Next.js and Nuxt allow flexible rendering per route, enabling optimal methods for different pages.

Glossary

• Pre-rendering: Creating HTML in advance (at build or on-demand).
• Hydration: Enabling interactivity in static HTML via JavaScript.
• Edge rendering: Executing rendering logic at CDN edge nodes for latency reduction.

Explore the capabilities of frameworks like Next.js, Gatsby, Nuxt, and SvelteKit for varying levels of SSR/SSG support. Start with the Next.js pre-rendering docs for guidance.

Conclusion and Further Reading

Recap

• SSG: best suited for static content, offering low costs and excellent CDN performance.
• SSR: ideal for dynamic, personalized content where real-time freshness is essential.
• Hybrid Approaches: Techniques like ISR and edge SSR offer a blend of performance and freshness.

Actionable Next Steps

1. Build a simple SSG blog using a static generator or fetch data with Next.js’s getStaticProps, then assess performance.
2. Convert a page (like /dashboard) to SSR and compare TTFB and resource usage.
3. Implement caching strategies and re-evaluate performance.

Further Reading (Authoritative Resources)

• Next.js — Pre-rendering: Static Generation and Server-side Rendering
• Rendering on the Web (Google / web.dev)
• JAMstack

Internal resources that may be beneficial:

• Redis caching patterns guide
• Monorepo vs Multi-repo Strategies (Beginners Guide)
• Web Development — Browser Storage Options (Beginners Guide)
• WSL Configuration Guide
• NAS Build Guide — Home Server (Beginners)

Try a mini project: Build an SSG blog, convert one page to SSR, then measure differences in Lighthouse scores and TTFB. Share your insights, as experimentation is key to understanding the trade-offs.