//
Server-Side Rendering (SSR) is the process of generating HTML on the server and sending a fully rendered page to the client. This contrasts with Client-Side Rendering (CSR), where the browser downloads a massive JavaScript bundle and renders the UI locally.
SSR provides better SEO (Search Engine Optimization) and a faster Time to First Contentful Paint (FCP).
While frameworks like Next.js handle SSR automatically, you can build your own custom SSR pipeline using React and Express.
npm install react react-dom express
You must use ReactDOMServer.renderToString() to convert your React components into an HTML string.
import express from 'express';
import React from 'react';
import ReactDOMServer from 'react-dom/server';
import App from './src/App';
const app = express();
app.get('/*', (req, res) => {
// Render the React component to an HTML string
const appHtml = ReactDOMServer.renderToString(<App />);
// Inject the string into the standard HTML skeleton
const html = `
<!DOCTYPE html>
<html>
<head>
<title>My SSR App</title>
</head>
<body>
<div id="root">\${appHtml}</div>
<!-- Load the client-side JS bundle to "hydrate" the app -->
<script src="/bundle.js"></script>
</body>
</html>
`;
res.send(html);
});
app.listen(3000);
When the browser receives the HTML, it displays it immediately. However, the page is not interactive yet. The browser must download the client-side JavaScript (bundle.js) and run ReactDOM.hydrateRoot() to attach event listeners to the existing HTML.
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