Registered once, the service worker sits in the request path: the page asks, the worker decides — cache first, network first, or a hand-built fallback when offline. That middle position is what makes offline-capable web apps possible and what makes PWAs more than a manifest.
The power comes with the classic footgun: a worker caching too aggressively serves a stale site to users who cannot fix it with refresh — the worker controls the refresh too. Versioned caches and a deliberate update flow are the price of the superpower.
Related terms
PWA
Progressive web app — a website that installs like an app: home-screen icon, offline behavior, push, all from the same URL.
HTTP caching
Headers that tell browsers and CDNs how long a response may be reused — the cheapest performance optimization that exists.
Client-side rendering (CSR)
Sending a JavaScript bundle that builds the page in the browser — flexible, but the first paint waits for the code to download and run.
The bench this belongs to
Full-stackIf you can describe it, we can build it. React and Next.js on the front, Python or Node behind, Postgres underneath, shipped to somewhere you can afford to run.
