This guide demonstrates how to set up server-side rendering (SSR) for React applications using @canonical/react-ssr. It covers everything from installation to building and handling SSR requests with client and server entry points.

Installation

First, install the @canonical/react-ssr package:

npm install @canonical/react-ssr

Quick Start

This section walks you through setting up SSR for your React app, including creating entry points, building your app, and handling SSR requests.

Entrypoints

You will notice that this setup encourages two entry points: one for the server, and one for the client. The server entry point includes the full application HTML for compatibility with streams. The client entry point includes just the application component, which is hydrated on the client.

Server-Side Entry Point

Create a server-side entry point to wrap your application and inject the necessary scripts and links into the HTML.

// src/ssr/entry-server.tsx
import Application from "../Application.js";
import React from "react";
import type {ReactServerEntrypointComponent, RendererServerEntrypointProps} from "@canonical/react-ssr/renderer";

// Define your server-side entry point component
const EntryServer: ReactServerEntrypointComponent<RendererServerEntrypointProps> = ({ lang = "en", scriptTags, linkTags }) => (
  <html lang={lang}>
    <head>
      <title>Canonical React SSR</title>
      {scriptTags}
      {linkTags}
    </head>
    <body>
      <div id="root">
        <Application />
      </div>
    </body>
  </html>
);

export default EntryServer;

This component is responsible for rendering the HTML structure and injecting the necessary script and link tags that are required for hydration on the client.

Client-Side Entry Point

Set up client-side hydration to rehydrate your app after the SSR content has been rendered.

// src/ssr/entry-client.tsx
import { hydrateRoot } from "react-dom/client";
import Application from "../Application.js";

// Hydrate the client-side React app after the server-rendered HTML is loaded
hydrateRoot(document.getElementById("root") as HTMLElement, <Application />);

Building your application

To build your SSR React app, use a tool like Vite, Webpack, or Next. The build process should include both client and server bundles. First, build the client-side app, then the server-side entry point. The example below uses Vite.

// package.json
{
  "scripts": {
    "build": "bun run build:client && bun run build:server",
    "build:client": "vite build --ssrManifest --outDir dist/client",
    "build:server": "vite build --ssr src/ssr/server.ts --outDir dist/server"
  }
}

Server Request Handling

Once your app is built, you can set up an Express server to handle SSR requests. See this file as an example.

Injecting the Client Application

Your client-side entry point must be executed by the client upon page load to rehydrate the server-rendered app.

Example for injecting the client application into your HTML with Vite:

<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Vite + React + TS</title>
  </head>
  <body>
    <div id="root"></div>
    <!-- Inject the client-side entry point -->
    <script type="module" src="/src/ssr/entry-client.tsx"></script>
  </body>
</html>

This script will hydrate the app on the client, connecting the React app to the server-rendered HTML.

Customization

You can inject additional bootstrapping scripts to customize the client-side setup. This is useful if you need more control over how the client app boots.

Bootstrap Scripts

You can pass custom modules, scripts, or inline script content to be executed on the client before the app is hydrated.

Options

bootstrapModules: An array of module paths. Generates <script type="module" src="{SCRIPT_LINK}"></script> elements.
bootstrapScripts: An array of script paths. Generates <script type="text/javascript" src="{SCRIPT_LINK}"></script> elements.
bootstrapScriptContent: Raw script content. Generates <script type="text/javascript">{SCRIPT_CONTENT}</script> elements.

import { JSXRenderer } from "@canonical/react-ssr/renderer";
// Pass custom bootstrap scripts to the renderer
const Renderer = new JSXRenderer(
  EntryServer, 
  { 
    htmlString, 
    renderToPipeableStreamOptions: {
       bootstrapModules: ["src/ssr/entry-client.tsx"] // Adds the client-side entry module to the page
    }
  }
);

The JSXRenderer also accepts renderToPipeableStreamOptions, which are passed to react-dom/server's renderToPipeableStream()`.

For further information, refer to React's renderToPipeableStream() documentation.

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Package last updated on 25 Sep 2025

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Install

@canonical/react-ssr