Service worker
A service worker is an event-driven script that can intercept requests within its scope and support offline behavior. It is separate from a page worker.
What it is
A service worker is an event-driven script that can intercept requests within its scope and support offline behavior. It is separate from a page worker.
Why it matters
It can serve cached assets when the network is unavailable, but its process may stop between events.
Example
A previously visited lesson can load from Cache Storage while offline; an unvisited lesson may still be unavailable.
Technical detail
Service workers normally require a secure context; localhost is a development exception. Extend asynchronous event work with event.waitUntil.
When to use it
Design installation, activation, updates, and offline failure pages together so a cached shell does not promise missing content.
Go deeper
Sources
More in Web platform
Assembled from the ReLU.chat curated knowledge base. These explanations are concise on purpose; check the sources for anything important.