🖥️ What is Server‑Side Rendering (SSR)?

Aug 23, 2025 • 3 min read

Server‑Side Rendering (SSR) is a foundational web technique that affects how quickly users see content and how well search engines can index your pages. This guide explains what SSR is, how it works, its benefits, and when you should use it.

What is Server‑Side Rendering?

With SSR, the server generates the full HTML for a page and sends it to the browser. Unlike Client‑Side Rendering (CSR), where the browser downloads JavaScript and builds the page after load, SSR delivers a fully rendered page that can be displayed immediately.

How SSR Works (Step‑by‑Step)

A user requests a URL.
The server fetches any required data.
The server executes code to build the complete HTML page.
The rendered HTML is sent to the browser.
The browser shows meaningful content immediately.
JavaScript then loads in the background and “hydrates” the page to enable interactivity where needed.

In contrast, CSR typically waits for JavaScript bundles to download before rendering, delaying first meaningful paint.

Benefits of SSR

Faster initial page load: HTML is ready when it reaches the browser, so users see content sooner.
Improved SEO: Crawlers can index fully rendered pages more reliably.
Better on low‑end devices: Rendering work is offloaded to the server.
Enhanced UX: Less waiting and fewer loading spinners.
Potential security benefits: Critical content is assembled server‑side.

Common Use Cases

Content‑heavy websites: Blogs, news, and marketing pages benefit from fast, crawlable content.
E‑commerce product pages: Frequently updated details (price, inventory) with fast first render.
Social feeds and portals: Personalized content at scale.
SaaS apps: Dashboards that mix static and dynamic data.
Real‑time data views: Stocks, live scores, and other frequently updated content.

Frameworks with SSR Support

Next.js (React): Hybrid SSR/SSG and API routes for full‑stack capabilities.
Angular Universal: SSR for Angular apps.
Nuxt.js (Vue): SSR plus static generation.

These tools pair SSR’s fast first render with client‑side hydration for rich interactivity.

Simple SSR Example (Next.js)

// pages/index.js
export async function getServerSideProps() {
  // Fetch data on the server before rendering
  const res = await fetch('https://api.example.com/posts');
  const posts = await res.json();
  return { props: { posts } };
}

export default function Home({ posts }) {
  return (
    <div>
      <h1>Blog Posts</h1>
      <ul>
        {posts.map((post) => (
          <li key={post.id}>{post.title}</li>
        ))}
      </ul>
    </div>
  );
}

getServerSideProps runs on the server at request time, so the HTML sent to the client already contains the data. This improves SEO and time‑to‑content.

When to Use SSR

SEO is a priority (blogs, marketing sites, docs).
Fast first contentful paint is critical for UX.
You need to support slow networks or low‑power devices.
Your app mixes static and dynamic content.
Each request requires backend processing.

Summary

Server‑Side Rendering (SSR) improves perceived performance and SEO by sending fully rendered HTML from the server, reducing the work browsers must do on first load. Modern frameworks make SSR approachable while preserving client‑side interactivity through hydration.