VietMX Staff asked 3 years ago
At its simplest, a service worker is a script that runs in the web browser and manages caching for an application.
Service workers function as a network proxy. They intercept all outgoing HTTP requests made by the application and can choose how to respond to them. For example, they can query a local cache and deliver a cached response if one is available. Proxying isn’t limited to requests made through programmatic APIs, such as fetch; it also includes resources referenced in HTML and even the initial request to index.html. Service worker-based caching is thus completely programmable and doesn’t rely on server-specified caching headers.
The service worker is preserved after the user closes the tab. The next time that browser loads the application, the service worker loads first, and can intercept every request for resources to load the application. Using a service worker to reduce dependency on the network can significantly improve the user experience.
