Service Worker (Web App)

A service worker is a browser-run script that sits between a web app and the network, intercepting requests to cache assets and serve them offline, enabling progressive web app behavior. It is generic web technology, not a maritime standard. On a content site like ShipCalculators a service worker can cache calculator pages and assets so a tool keeps working with poor or intermittent connectivity, the condition aboard ships outside reliable VSAT or Starlink coverage. It runs on a separate thread from the page and cannot touch the DOM directly.