Service Workers & PWAs
20 min read
Service WorkerPWAOfflineCache APIManifestApp Shell
Service Workers: Offline-First Architecture
A Service Worker is a JavaScript file that runs in a separate thread, intercepting network requests and enabling offline functionality.
Lifecycle
- Register: navigator.serviceWorker.register('/sw.js')
- Install: Pre-cache critical assets
- Activate: Clean up old caches
- Fetch: Intercept requests and serve from cache or network
Caching Strategies
- Cache First: Try cache, fallback to network (static assets)
- Network First: Try network, fallback to cache (API data)
- Stale While Revalidate: Serve cache, update in background
PWA Requirements
- HTTPS
- Service Worker
- Web App Manifest (name, icons, theme_color)