How to Integrate Service Workers in Next.js Applications

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Service workers are scripts that tally successful nan inheritance to supply powerful caching capabilities and different features to modern web applications.

These features bring nan seamless and user-friendly acquisition of autochthonal apps to nan web browser.

Service workers are a basal constituent successful nan creation of Progressive Web Apps (PWAs).

Understanding Service Workers

A work worker is simply a type of JavaScript web worker that runs successful nan background, abstracted from nan main JavaScript thread, truthful that it’s non-blocking. This intends that it does not origin delays aliases interruptions to nan application's personification interface aliases nan user's relationship pinch it.

Laptop show pinch codification connected nan surface and a pen holder pinch pens connected nan side.

Service workers usability arsenic proxy servers—sitting betwixt web applications and nan network. They tin intercept requests and responses, cache resources, and supply offline support. This helps to guarantee that web apps consciousness much seamless and user-friendly, moreover erstwhile nan personification is not online.

Key Applications for Service Workers

There are respective applications for work workers. They include:

  • PWAs: Service workers supply awesome powerfulness to Progressive Web Apps. They execute civilization web requests, push notifications, offline support, and accelerated loading.
  • Caching: Service workers tin shop nan application's assets—images, JavaScript code, and CSS files—in nan browser's cache storage. This lets nan browser retrieve them from its cache alternatively than fetching them from nan distant server complete nan network. As a result, contented loads faster, which is peculiarly useful for users pinch slow aliases unreliable net connections.
  • Background sync: Service workers tin synchronize information and tally different inheritance tasks, moreover erstwhile nan personification is not actively interacting pinch nan exertion aliases erstwhile nan exertion is not unfastened successful nan browser.

Integrating Service Workers successful Next.js Applications

Before diving into nan code, it helps to understand really work workers work. There are 2 cardinal phases of utilizing work workers: registration and activation.

During nan first phase, nan browser registers nan work worker. Here’s a elemental example:

const registerServiceWorker = async () => {
  if ("serviceWorker" in navigator) {
    registration = await navigator.serviceWorker.register("/sw.js");


The codification first checks if nan browser supports work workers, which each modern web browsers do. If this support exists, it proceeds to registry a work worker located astatine nan specified record path.

In nan activation phase, you request to instal and activate a work worker by listening to nan install and activate events utilizing JavaScript arena listeners. Here is really you tin execute this:

registration.addEventListener("install", () => {
    console.log("Service worker installed");

registration.addEventListener("activate", () => {
    console.log("Service worker activated");

You tin see this codification correct aft nan registration process. It should tally correct aft nan work worker registration process is successful.

You tin find this project's codification successful its GitHub repository.

Create a Next.js Project

To get started, tally this bid to scaffold a Next.js task locally:

npx create-next-app next-project

Adding a work worker to a Next.js exertion involves nan pursuing steps:

  1. Register a work worker successful nan world scope environment.
  2. Create a work worker JavaScript record successful nan nationalist directory.

Adding a Service Worker

First, registry a work worker. Update nan src/pages/_app.js record arsenic follows. Including nan codification successful this record ensures that nan work worker registers erstwhile nan exertion loads and has entree to each nan application's assets.

import { useEffect } from 'react';

export default function App({ Component, pageProps }) {
  useEffect(() => {
    if ('serviceWorker' in navigator) {
        .register('/service-worker.js', { scope: '/' })
        .then((registration) => {
            'Service worker registered successfully. Scope:',
        .catch((error) => {
          console.error('Service worker registration failed:', error);
  }, []);

  return <Component {...pageProps} />;

The useEffect hook triggers erstwhile nan constituent mounts. Like nan erstwhile example, nan codification first checks if nan user's browser supports work workers.

If nan support exists, it registers nan work worker book located astatine nan specified record path, and specifies its scope arsenic “/. This intends nan work worker has power of each resources successful nan application. You tin supply a much granular scope if you want, e.g., “/products”.

If nan registration is successful, it logs a occurrence message, on pinch its scope. If there’s an correction during nan registration process, nan codification will drawback it and log an correction message.

Install and Activate nan Service Worker

Add nan pursuing codification to a caller file, public/service-worker.js.

const installEvent = () => {
  self.addEventListener('install', () => {
    console.log('service worker installed!!!!');

const activateEvent = () => {
  self.addEventListener('activate', () => {
    console.log('service worker activated!!!');


To trial if nan work worker has been successfully registered, installed, and activated, commencement nan improvement server and unfastened your exertion successful nan browser.

npm tally dev

Open Chrome’s Developer Tools model (or your browser’s equivalent), and navigate to nan Application tab. Under nan Service Workers section, you should spot nan work worker that you person registered.

Chrome Developer devices work worker tab showing an installed and progressive work worker up and running.

With nan work worker successfully registered, installed, and activated, you tin instrumentality respective functions for illustration caching, inheritance sync, aliases sending push notifications.

Caching Resources With Service Workers

Caching exertion assets connected nan user's instrumentality tin amended capacity by allowing for quicker access, particularly successful situations pinch unreliable net connections.

To cache nan app's assets, see nan pursuing codification successful nan service-worker.js file.

const cacheName = 'test-cache';

self.addEventListener('fetch', (event) => {
    caches.match(event.request).then((cachedResponse) => {
      return cachedResponse || fetch(event.request).then((response) => {
        return => {
          cache.put(event.request, response.clone());
          return response;

When a personification first accesses nan location page, this codification checks if location is simply a cached consequence for nan petition successful nan cache. If a cached consequence exists, nan work returns it to nan client.

If nary cached consequence exists, nan work worker fetches nan assets from nan server complete nan network. It serves nan consequence to nan customer and caches it for early requests.

To position nan cached assets, unfastened nan Application tab successful nan developer tools. Under nan Cache Storage section, you should spot a database of nan cached assets. You tin besides cheque nan Offline option nether nan Service Worker conception and reload nan page to simulate an offline experience.

Chrome Developer devices cache retention showing a database of cached assets.

Now, erstwhile you sojourn nan homepage, nan browser will service resources stored successful nan cache retention alternatively of attempting to make web requests to fetch data.

Using Service Workers to Enhance Performance

Service workers are a powerful instrumentality for enhancing nan capacity of Next.js apps. They tin cache resources, intercept requests, and supply offline support, each of which tin amended nan personification experience.

However, it’s important to statement that work workers tin besides beryllium analyzable to instrumentality and manage. It’s important to cautiously see nan imaginable benefits and drawbacks of work workers earlier you usage them.

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