ServiceWorkers (formerly Navigation Controllers) are a new system that provides event-driven scripts that run independent of web pages. They are similar to SharedWorkers except that their lifetime is different and they have access to domain-wide events such as network fetches. Use cases: offline, reducing perceived page load latency and will eventually power notification/push/sync/... use cases.
Specification currently under development in a Working Group
Status in Chromium
Enabled by default
Consensus & Standardization
Last updated on 2020-11-09