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Yug Jadvani Published on Dec 22 • 3 min read

Mastering Server-Side Rendering (SSR) in React 19 with Vite: The Ultimate Guide for Developers

React has always been a game-changer in frontend development, and with the release of React 19, it has become even more powerful and efficient. In this blog, we will delve into server-side rendering (SSR) in React 19 using Vite, a blazing-fast build tool. Whether you're a beginner or an advanced developer, this guide is crafted to make SSR approachable and actionable.

What’s New in React 19?

React 19 introduces several key updates:

  • Improved Server Components: A new way to build applications with a seamless integration of server-rendered and client-rendered components.

  • Streaming Rendering: Enhanced performance through React’s ability to stream content to the browser.

  • Concurrent Rendering: Allows smoother user interfaces by prioritizing tasks dynamically.

These features make React 19 an ideal candidate for implementing SSR with modern tools like Vite.

Understanding Server-Side Rendering (SSR)

Server-side rendering involves rendering React components on the server and sending the HTML to the client. Unlike client-side rendering (CSR), where the browser handles rendering, SSR provides:

  • Faster Initial Load: The browser receives a fully-rendered HTML page.

  • SEO Benefits: Content is available for search engine crawlers immediately.

  • Improved User Experience: Users see content sooner, even on slower connections.

How Does SSR Work in React 19?

With React 19’s streaming and concurrent features, SSR becomes more efficient. Components are streamed as they’re ready, reducing server response time and enhancing interactivity.

Why Use Vite for SSR?

Vite is a modern build tool known for its speed and simplicity. With its advanced features like fast module resolution and hot module replacement (HMR), Vite is an excellent choice for integrating SSR in React 19 projects.

Key Benefits of Vite in SSR:

  1. Lightning-Fast Builds: Optimized development and production workflows.

  2. Simple Configuration: Minimal boilerplate setup.

  3. Native Support for React: Built-in support for JSX, TypeScript, and modern libraries.

  4. Scalable Architecture: Handles large projects efficiently.

Step-by-Step Guide to Setting Up SSR in React 19 with Vite

Let’s build an SSR-enabled React 19 app with Vite from scratch. Follow these steps to get started:

1. Initialize the Project 

npm create vite@latest my-react-ssr-app --template react
cd my-react-ssr-app
npm install
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2. Install Necessary Dependencies 

npm install express @vitejs/plugin-react react-dom/server
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3. Set Up Vite Configuration

Edit vite.config.js to enable SSR:

import { defineConfig } from 'vite';
import react from '@vitejs/plugin-react';

export default defineConfig({
  plugins: [react()],
  build: {
    ssr: true,
    rollupOptions: {
      input: './server/index.js',
    },
  },
});
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4. Create a Simple React Component

Create src/App.jsx:

function App() {
  return (
    <div>
      <h1>Welcome to React 19 SSR with Vite</h1>
      <p>This page is server-side rendered!</p>
    </div>
  );
}
export default App;
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5. Set Up an Express Server

Create server/index.js:

import express from 'express';
import { renderToString } from 'react-dom/server';
import App from '../src/App';

const app = express();

app.use('/static', express.static('dist'));

app.get('*', (req, res) => {
  const appHtml = renderToString(<App />);

  const html = `
    <!DOCTYPE html>
    <html lang="en">
    <head>
      <meta charset="UTF-8" />
      <meta name="viewport" content="width=device-width, initial-scale=1.0" />
      <title>React 19 SSR with Vite</title>
    </head>
    <body>
      <div id="app">${appHtml}</div>
      <script src="/static/client.js"></script>
    </body>
    </html>
  `;

  res.send(html);
});

app.listen(3000, () => {
  console.log('Server is running on http://localhost:3000');
});
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6. Build and Run

To build and serve your SSR app:

npm run build
node server/index.js
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Visit http://localhost:3000 to see your SSR React app in action.

Examples and Best Practices

Streaming SSR Example

React 19’s renderToPipeableStream allows streaming:

import { renderToPipeableStream } from 'react-dom/server';

app.get('*', (req, res) => {
  const stream = renderToPipeableStream(<App />, {
    onShellReady() {
      res.status(200).setHeader('Content-Type', 'text/html');
      stream.pipe(res);
    },
    onError(err) {
      console.error(err);
      res.status(500).send('Internal Server Error');
    },
  });
});
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This approach renders content progressively, enhancing performance.

SEO Considerations

  • Use proper <meta> tags for description and keywords.

  • Implement a sitemap for dynamic pages.

Notes and Tips

  • Always test SSR performance using tools like Lighthouse.

  • Keep server logic minimal to ensure scalability.

  • Use environment variables to manage sensitive data.

Conclusion

With React 19’s advanced features and Vite’s modern build capabilities, server-side rendering becomes seamless and efficient. Whether you're optimizing for SEO or improving user experience, SSR with React 19 and Vite is a winning combination.

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