Quickstart ​

This page provides the bare-minimum overview on how to start building with WebContainer API.

The WebContainer API starter is the fastest way to explore the API. Open it in StackBlitz editor:

or in Codeflow IDE, our full-fledged web environment:

If you prefer to develop locally, follow the steps below.

Install WebContainer API ​

To install the WebContainer API, run the following code in the terminal while inside your project folder:

npm i @webcontainer/api

npm i @webcontainer/api

1. Create a WebContainer instance ​

To create a WebContainer instance, import WebContainer from @webcontainer/api in a JavaScript file and call the boot method:

import { WebContainer } from '@webcontainer/api';

// Call only once
const webcontainerInstance = await WebContainer.boot();

import { WebContainer } from '@webcontainer/api';

// Call only once
const webcontainerInstance = await WebContainer.boot();

Cross-Origin Isolation ​

WebContainers require SharedArrayBuffer, which, in turn, requires the website where they are running to be cross-origin isolated. Because of that, you'll need to set COOP/COEP headers:

Cross-Origin-Embedder-Policy: require-corp
Cross-Origin-Opener-Policy: same-origin

Cross-Origin-Embedder-Policy: require-corp
Cross-Origin-Opener-Policy: same-origin

To learn more about this topic and see how to do it, check Configuring Headers.

2. Working with the file system ​

The API provides an fs object to work with the file system. You can read more about them on the File System page.

Currently, the following methods are available:

• readFile, which reads a file system,
• readdir, which asynchronously reads the contents of a given directory,
• rm, which is used to delete a file at the given path (handy with resetting examples),
• writeFile, which is used to write to a file or create it,
• mkdir, which creates a directory.

To load your files into the WebContainer, use the mount method which will "copy" them into the file system:

await webcontainerInstance.mount(projectFiles);

await webcontainerInstance.mount(projectFiles);

3. Running commands and processes ​

Add methods to start and exit the dev server, as well as to run the WebContainer instance:

async function startDevServer() {
  const installProcess = await webcontainerInstance.spawn('npm', ['install']);

  const installExitCode = await installProcess.exit;

  if (installExitCode !== 0) {
    throw new Error('Unable to run npm install');
  }

  // `npm run dev`
  await webcontainerInstance.spawn('npm', ['run', 'dev']);
}

async function startDevServer() {
  const installProcess = await webcontainerInstance.spawn('npm', ['install']);

  const installExitCode = await installProcess.exit;

  if (installExitCode !== 0) {
    throw new Error('Unable to run npm install');
  }

  // `npm run dev`
  await webcontainerInstance.spawn('npm', ['run', 'dev']);
}

4. Preview ​

After you have started the dev server, get the URL from port-ready event and mount it in an iframe:

webcontainerInstance.on('server-ready', (port, url) => (iframeEl.src = url));

webcontainerInstance.on('server-ready', (port, url) => (iframeEl.src = url));

where iframeEl is the reference to your iframe.

And that's it! You have successfully set up your first WebContainer app 🥳

Before you deploy - serve over HTTPS ​

Please note that your deployed page must be served over HTTPS. This is not necessary when developing locally, as localhost is exempt from some browser restrictions, but there is no way around it once you deploy to production.

Next steps ​

We also prepared a thorough step-by-step tutorial if you learn best with walkthroughs.

If you'd like to explore the API on your own, you can check out the API Reference or see the projects made by our Community.