Service Workers (SW)

A JS worker that runs between the browser and network.

Can intercept requests, serve cached responses, enable offline pages, and run background tasks (push, sync).

Requires HTTPS (or localhost for dev).

Adds complexity and subtle bugs. Caching logic is error-prone and easily serves stale pages to visitors.

You must design update semantics (skipWaiting, cache versioning) or users will see old assets.

Debugging and lifecycle issues consume time.

Not needed if you do not need offline access or push notifications.

SW could be useful if:

• You want offline reading for notes.

• You want to present a snappy cached shell for repeat visitors.

• You plan to add a PWA experience or push notifications.