SPA Mode
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SPA Mode

From the beginning, Remix's opinion has always been that you own your server architecture. This is why Remix is built on top of the Web Fetch API and can run on any modern runtime via built-in or community-provided adapters. While we believe that having a server provides the best UX/Performance/SEO/etc. for most apps, it is also undeniable that there exist plenty of valid use cases for a Single Page Application in the real world:

  • You don't want to manage a server and prefer to deploy your app via static files on Github Pages or another CDN
  • You don't want to run a Node.js server
  • You want to migrate a React Router app to Remix
  • You're developing a special type of embedded app that can't be server rendered
  • "Your boss couldn't care less about the UX ceiling of SPA architecture and won't give your dev teams time/capacity to re-architect things" - Kent C. Dodds

That's why we added support for SPA Mode in 2.5.0 (RFC), which builds heavily on top of the Client Data APIs.

SPA Mode requires your app to be using Vite and the Remix Vite Plugin

What is SPA Mode?

SPA Mode is basically what you'd get if you had your own React Router + Vite setup using createBrowserRouter/RouterProvider, but along with some extra Remix goodies:

  • File-based routing (or config-based via routes())
  • Automatic route-based code-splitting via route.lazy
  • <Link prefetch> support to eagerly prefetch route modules
  • <head> management via Remix <Meta>/<Links> APIs

SPA Mode tells Remix that you do not plan on running a Remix server at runtime and that you wish to generate a static index.html file at build time and you will only use Client Data APIs for data loading and mutations.

The index.html is generated from the HydrateFallback component in your root.tsx route. The initial "render" to generate the index.html will not include any routes deeper than root. This ensures that the index.html file can be served/hydrated for paths beyond / (i.e., /about) if you configure your CDN/server to do so.

Usage

You can get started quickly using the SPA Mode template in the repo:

npx create-remix@latest --template remix-run/remix/templates/spa

Or, you can manually opt-into SPA mode in your Remix+Vite app by setting ssr: false in your Remix Vite plugin config:

// vite.config.ts
import { vitePlugin as remix } from "@remix-run/dev";
import { defineConfig } from "vite";

export default defineConfig({
  plugins: [
    remix({
      ssr: false,
    }),
  ],
});

Development

In SPA Mode, you develop the same way you would for a traditional Remix SSR app, and you actually use a running Remix dev server in order to enable HMR/HDR:

remix vite:dev

Production

When you build your app in SPA Mode, Remix will call the server handler for the / route and save the rendered HTML in an index.html file alongside your client side assets (by default build/client/index.html).

remix vite:build

Preview

You can preview the production build locally with vite preview:

npx vite preview

vite preview is not designed for use as a production server

Deployment

To deploy, you can serve your app from any HTTP server of your choosing. The server should be configured to serve multiple paths from a single root /index.html file (commonly called "SPA fallback"). Other steps may be required if the server doesn't directly support this functionality.

For a simple example, you could use sirv-cli:

npx sirv-cli build/client/ --single

Or, if you are serving via an express server (although at that point you may want to consider just running Remix in SSR mode 😉):

app.use("/assets", express.static("build/client/assets"));
app.get("*", (req, res, next) =>
  res.sendFile(
    path.join(process.cwd(), "build/client/index.html"),
    next
  )
);

Hydrating a div instead of the full document

If you don't want to hydrate the full HTML document, you can choose to use SPA mode and only hydrate a sub-section of the document such as <div id="app"> with a few minor changes.

1. Add an index.html file

Since Remix won't render the HTML document, you will need to provide that HTML outside of Remix. The easiest way to do this is to just keep an app/index.html document with a placeholder you can replace with the Remix rendered HTML at build time to generate the final index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>My Cool App!</title>
  </head>
  <body>
    <div id="app"><!-- Remix SPA --></div>
  </body>
</html>

The <!-- Remix SPA --> HTML comment is what we'll replace with the Remix HTML.

Because whitespace is meaningful in the DOM/VDOM tree - it's important not to include any spaces around it and the surrounding div, otherwise you will run into React hydration issues

2. Update root.tsx

Update your root route to render just the contents of <div id="app">:

export function HydrateFallback() {
  return (
    <>
      <p>Loading...</p>
      <Scripts />
    </>
  );
}

export default function Component() {
  return (
    <>
      <Outlet />
      <Scripts />
    </>
  );
}

3. Update entry.server.tsx

In your app/entry.server.tsx file, you'll want to take the Remix-rendered HTML and insert it into your static app/index.html file placeholder. You'll also want to stop pre-pending the <!DOCTYPE html> declaration like the default entry.server.tsx file does since that should be in your app/index.html file).

import fs from "node:fs";
import path from "node:path";

import type { EntryContext } from "@remix-run/node";
import { RemixServer } from "@remix-run/react";
import { renderToString } from "react-dom/server";

export default function handleRequest(
  request: Request,
  responseStatusCode: number,
  responseHeaders: Headers,
  remixContext: EntryContext
) {
  const shellHtml = fs
    .readFileSync(
      path.join(process.cwd(), "app/index.html")
    )
    .toString();

  const appHtml = renderToString(
    <RemixServer context={remixContext} url={request.url} />
  );

  const html = shellHtml.replace(
    "<!-- Remix SPA -->",
    appHtml
  );

  return new Response(html, {
    headers: { "Content-Type": "text/html" },
    status: responseStatusCode,
  });
}

You may need to run npx remix reveal if you don't currently have an app/entry.server.tsx file in your app

4. Update entry.client.tsx

Update app/entry.client.tsx to hydrate the <div id="app"> instead of the document:

import { RemixBrowser } from "@remix-run/react";
import { startTransition, StrictMode } from "react";
import { hydrateRoot } from "react-dom/client";

startTransition(() => {
  hydrateRoot(
    document.querySelector("#app"),
    <StrictMode>
      <RemixBrowser />
    </StrictMode>
  );
});

You may need to run npx remix reveal if you don't currently have an app/entry.client.tsx file in your app

Notes/Caveats

  • SPA Mode only works when using Vite and the Remix Vite plugin

  • You cannot use server APIs such as headers, loader, and action -- the build will throw an error if you export them

  • You can only export a HydrateFallback from your root.tsx in SPA Mode -- the build will throw an error if you export one from any other routes.

  • You cannot call serverLoader/serverAction from your clientLoader/clientAction methods since there is no running server -- those will throw a runtime error if called

  • It's important to note that Remix SPA mode generates your index.html file by performing a "pre-render" of your root route on the server during the build

    • This means that while you're creating a SPA, you still have a "server build" and "server render" step, so you do need to be careful about using dependencies that reference client-only aspects such as document, window, localStorage, etc.
    • Generally speaking, the way to resolve these issues is to import any browser-only libraries from entry.client.tsx so they don't end up in the server build
    • Otherwise, you can generally solve these by using React.lazy or the <ClientOnly> component from remix-utils.

Migrating from React Router

We also expect SPA Mode to be useful in helping folks migrate existing React router apps over to Remix apps (SPA or not!).

The first step towards this migration is getting your current React Router app running on vite, so that you've got whatever plugins you need for your non-JS code (i.e., CSS, SVG, etc.).

If you are currently using BrowserRouter

Once you're using vite, you should be able to drop your BrowserRouter app into a catch-all Remix route per the steps in the this guide.

If you are currently using RouterProvider

If you are currently using RouterProvider, then the best approach is to move your routes to individual files and load them via route.lazy:

  • Name these files according to the Remix file conventions to make the move to Remix (SPA) easier
  • Export your route components as a named Component export (for RR) and also a default export (for eventual use by Remix)

Once you've got all your routes living in their own files, you can:

  • Move those files over into the Remix app/ directory
  • Enable SPA Mode
  • Rename all loader/action function to clientLoader/clientAction
  • Replace your React Router index.html file with an app/root.tsx route that exports a default component and HydrateFallback
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