Service Worker
Service Worker
A program that runs in the background of a web browser to enable offline pages and push notifications.
In Simple Terms
A service worker is a program that handles background tasks behind the scenes of a web page. It keeps pages viewable even when the internet connection drops, and it delivers notifications from a website to your phone. By caching data it has already loaded, it lets pages open quickly even in places with unstable connectivity.
Behind the Name
The name comes from the idea of a background worker that keeps a web service running smoothly. "Service" refers to the web service or functionality it supports, while "Worker" reflects the fact that it operates automatically, without any direct input from the user. Together, the name captures its role as a behind-the-scenes helper that supports a website without ever appearing on screen.
Take a Closer Look!
A service worker is a program that a web browser runs behind the scenes, separately from the web page itself.
Unlike a regular web page, it doesn't directly control what's shown on screen — instead, it handles things like managing network requests in the background.
In short, it sits between a website and the internet, checking the traffic that passes through.
By storing data locally on your computer or phone after your first visit, it allows pages to be displayed even when you're offline.
It can also use that cached data to dramatically speed up page loading.
It's also used for push notifications — letting a site send you messages even when it isn't open — and for syncing data in the background.
This makes it possible to give websites an experience similar to a smartphone app.
For security reasons, service workers are only allowed to run over encrypted, secure connections.