# Chrome Extension SDK 2.0

We're excited to release version 2.0 of the Chrome Extension SDK. Version 2.0 comes with the new `createClerkClient()` helper for background service workers, improved support for syncing auth state with your web application and detailed documentation for the SDK.

Take a look at our [Chrome Extension Quickstart](https://clerk.com/docs/quickstarts/chrome-extension.md) if you're just getting started, or read over the [Chrome Extension documentation](https://clerk.com/docs/quickstarts/chrome-extension.md) to learn about all of the features.

Our [Chrome Extension Quickstart repo](https://github.com/clerk/clerk-chrome-extension-quickstart) and [Chrome Extension Demo repo](https://github.com/clerk/clerk-chrome-extension-demo) are a great reference or starting point for a project.

## Introducing `createClerkClient()` for Service Workers

Chrome Extensions pose a unique challenge for developers using Clerk. When the popup or side panel is closed, the Clerk session cookie will become stale. The `createClerkClient()` function is specifically designed to allow extension developers to refresh the user's session, obtain a valid token or other auth, and retrieve user data.

filename: src/background/index.ts
```ts
import { createClerkClient } from '@clerk/chrome-extension/background'

const publishableKey = process.env.PLASMO_PUBLIC_CLERK_PUBLISHABLE_KEY

// create a new Clerk instance and get a fresh token for the user
async function getToken() {
  const clerk = await createClerkClient({
    publishableKey,
  })

  // if there is no user session, then return nothing
  if (!clerk.session) {
    return null
  }

  // return the user's token
  return await clerk.session?.getToken()
}

// create a listener to listen for messages from content scripts
chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
  console.log('Handling request for the users current token')

  getToken()
    .then((token) => {
      sendResponse({ token })
    })
    .catch((error) => {
      console.error('[Service Worker]: Error occured -> ', JSON.stringify(error))
      sendResponse({ token: null })
    })

  return true // REQUIRED: Indicates that the listener responds asynchronously.
})
```

You can now send a message from a content script to the background service worker and get auth status or a token for the user.

filename: src/tabs/content.tsx
```tsx
// send a message to the background service worker
chrome.runtime.sendMessage({ greeting: 'get-token' }, (response) => {
  // you can now have access to the user's token
  console.log(response.token)
})
```

## Breaking Changes

- `syncSessionWithTab` has been removed and replaced with `syncHost`. [Changelog](https://github.com/clerk/javascript/blob/main/packages/chrome-extension/CHANGELOG.md) [Sync Host Guide](https://clerk.com/docs/references/chrome-extension/sync-host.md)
- The `storage` host permission is now required. [Changelog](https://github.com/clerk/javascript/blob/main/packages/chrome-extension/CHANGELOG.md)