javascript – What is service worker in react js-ThrowExceptions

Exception or error:

When creating a react app, service worker is invoked by default. Why service worker is used? What is the reason for default invoking?

How to solve:

You may not need a service worker for your application. If you are creating a project with create-react-app it is invoked by default

Service workers are well explained in this article. To Summarise from it

A service worker is a script that your browser runs in the
background, separate from a web page, opening the door to features
that don’t need a web page or user interaction. Today, they already
include features like push notifications and background sync and have
ability to intercept and handle network requests, including
programmatically managing a cache of responses.

In the future, service workers might support other things like
periodic sync or geofencing.

According to this PR to create-react-app

Service workers are introduced with create-react-app via

Using a server worker with a cache-first strategy offers performance
advantages, since the network is no longer a bottleneck for fulfilling
navigation requests. It does mean, however, that developers (and
users) will only see deployed updates on the “N+1”
visit to a page, since previously cached resources are updated in the

The call to register service worker is enabled by default in new apps but you can always remove it and then you’re back to regular behaviour.


In simple and plain words, it’s a script that browser runs in the background and has whatsoever no relation with web pages or the DOM, and provide out of the box features. It also helps you cache your assets and other files so that when the user is offline or on slow network.

Some of these features are proxying network requests, push notifications and background sync. Service workers ensure that the user has a rich offline experience.

You can think of the service worker as someone who sits between the client and server and all the requests that are made to the server pass through the service worker. Basically, a middle man. Since all the request pass through the service worker, it is capable to intercept these requests on the fly.

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