Extension service worker basics

Extension service workers are installed and updated differently from web service workers. This page explains those differences.

Register service workers

To register an extension service worker, specify it in the "background" field of the manifest.json file. Use the "service_worker" key, which specifies a single JavaScript file. Service workers in web pages or web apps register service workers by first feature-detecting for serviceWorker in navigator then calling register() inside feature detection. This does not work for extensions.

  "name": "Awesome Test Extension",
  "background": {
    "service_worker": "service-worker.js"

Import scripts

There are two methods of importing scripts into a service worker: the import statement and the importScripts() method. Note that import(), often called a dynamic import, is not supported.

To use the import statement, add the "type" field to your manifest and specify "module". For example:

  "background": {
    "service_worker": "service-worker.js",
    "type": "module"

Then use import as you normally would. Note that import assertions are not supported.

import { tldLocales } from './locales.js';

Use importScripts() as you would in a web service worker.



To update the service worker, publish a new version of your extension to the Chrome Web Store. You cannot get around this by loading your extension from a server. For security reasons Manifest V3 does not support remotely-hosted code. Your service worker must be part of the extension package.