PWAs bridge the gap between web and native apps. At Google, we're big believers — many of our products are PWAs.
What Makes a PWA?
- Web App Manifest: Metadata for "Add to Home Screen"
- Service Worker: Offline support and caching
- HTTPS: Required for Service Workers
The Manifest
Installability Criteria
- Valid web app manifest with required fields
- Served over HTTPS
- Registered Service Worker with a fetch handler
- Icons in correct sizes (192px and 512px minimum)
Offline Strategies
App Shell Model
Cache the application shell (HTML, CSS, JS) and load dynamic content from the network. Users see the app structure immediately.
Offline-First Data
Push Notifications
Performance Tips
- Precache critical resources during SW install
- Use navigation preload to avoid SW startup delay
- Lazy-load non-critical resources
- Use Workbox for production-grade caching