Progressive Web Apps (PWAs) hit their decade mark in 2025. The 2026 reality: PWAs are real, useful, and underused. The interview probes whether you understand the technical components, the platform realities, and when a PWA is the right choice over a native app.
What makes a PWA
Three core components:
- Web App Manifest: declares the app metadata (name, icons, theme color, display mode)
- Service Worker: for offline support and background sync
- HTTPS: required (except localhost)
Together: a website that can be installed, run offline, and feel app-like.
The manifest
JSON file at /manifest.json linked from HTML:
{
"name": "My App",
"short_name": "App",
"icons": [
{ "src": "/icon-192.png", "sizes": "192x192", "type": "image/png" },
{ "src": "/icon-512.png", "sizes": "512x512", "type": "image/png" }
],
"start_url": "/",
"display": "standalone",
"theme_color": "#000000",
"background_color": "#ffffff"
}Display modes
- browser: opens in browser tab (basically not a PWA)
- standalone: own window, no browser chrome — feels native
- fullscreen: covers status bar, like games
- minimal-ui: minimal browser controls
Install prompts
Browsers show “Install” prompts on engaged users:
- Manifest valid
- Service Worker registered
- HTTPS
- User has visited multiple times or spent significant time
You can trigger custom install UI via the beforeinstallprompt event.
Offline-first patterns
Strategies enabled by Service Worker:
- App Shell: cache the UI shell so the app loads offline; data fetched as available
- Offline page: show a custom page when offline and resource not cached
- Background sync: queue user actions; sync when online
- Read-only offline: last-known content available; writes disabled
iOS PWA quirks
Safari has historically been the weakest PWA browser:
- “Add to Home Screen” install path; no install prompt
- Service Worker support is partial
- Background sync not supported
- Push notifications added in iOS 16.4 (2023) but with quirks
Modern iOS PWAs work but are second-class citizens compared to Android.
Android PWA support
Strong:
- Install prompt
- Service Worker fully supported
- Background sync, push, advanced features
- Trusted Web Activity (TWA) for Play Store distribution
Push notifications
PWA push:
- User grants permission
- Service Worker subscribes to push service
- Server sends push via Web Push protocol (VAPID)
- Service Worker receives and shows notification
Works on desktop and Android. iOS support exists but with limitations.
When to choose PWA over native
PWA wins when:
- You already have a web app and want mobile UX
- App store distribution is undesirable
- Cross-platform (one codebase) matters
- Update velocity matters (no app store review)
Native wins when:
- You need deep platform integration (HealthKit, ARKit, deep iOS / Android features)
- Performance must match native
- App store presence is a marketing channel
- iOS users are critical (PWA on iOS still has gaps)
Hybrid approach
Some apps wrap a PWA in a native shell:
- Capacitor / Cordova for cross-platform native
- Tauri / Electron for desktop
- TWA (Trusted Web Activity) on Android for Play Store distribution
Trade-off: development simplicity vs full native fidelity.
Common mistakes
- Manifest missing or invalid (browser does not show install)
- Service Worker caches old code; users stuck on stale version
- Offline UX is broken (white screen instead of meaningful fallback)
- Forgetting iOS-specific testing
Frequently Asked Questions
Are PWAs in the App Store?
Apple has historically resisted; Google’s TWA puts PWAs in Play Store. Microsoft Store accepts PWAs.
How do I detect if my app is installed as a PWA?
Check display-mode media query: matchMedia('(display-mode: standalone)'). Returns true for installed PWAs.
What is the difference between PWA and SPA?
SPA = Single Page App (architecture). PWA = Progressive Web App (capabilities). They overlap; not the same thing. A SPA can be a PWA; a PWA can be multi-page.