Progressive Web App (PWA)
A type of application software delivered through the web, built using common web technologies including HTML, CSS, and JavaScript.
Detailed Explanation
PWAs are designed to work on any platform that uses a standards-compliant browser, including both desktop and mobile devices. They offer features previously reserved for native apps, such as offline support, push notifications, and the ability to be 'installed' on a home screen. They rely on Service Workers to cache assets and provide a fast, reliable experience regardless of network quality.
Quick Summary
A progressive web app is a website that uses web manifests, service workers, and HTTPS to behave like a native app: installable, offline-capable, and able to send push notifications, without an app store.
Key Takeaways
- A valid PWA requires HTTPS, a web manifest with icons, and a service worker that handles offline.
- Chrome and Edge auto-prompt users to install qualifying PWAs; iOS Safari requires manual Add to Home Screen.
- Once installed, a PWA runs in its own window and the service worker controls how the network is used.
- PWAs bypass app store review and revenue cuts, but lose access to deep OS integrations like background services.
- iOS support has historically lagged Android; storage quotas and background features remain more limited.
When to use it
- Content sites that want repeat visitors to install a home-screen icon for one-tap access.
- Productivity apps where offline editing and reliable performance on flaky networks matter.
- Mobile-first markets where app-store distribution is costly or download size is a barrier.
- Internal tools deployed across heterogeneous device fleets without IT-managed installation.
Common Mistakes
- Caching the index.html in the service worker without a version-busting strategy, then deploying an update that users never receive.
- Skipping the offline fallback page, so users see Chrome's dinosaur instead of branded UI when offline.
- Forgetting that service workers run on their own thread and cannot access the DOM or main-thread globals.
- Treating PWA as a replacement for native when the app needs background location, contacts, or Bluetooth, gaps remain.
Progressive Web App (PWA), Frequently Asked
Do PWAs work on iOS?
Partially. Safari supports service workers, web app manifests, and Add to Home Screen, but push notifications were only added in iOS 16.4 and several APIs (Web Bluetooth, NFC) remain unavailable.
Are PWAs better than native apps?
They are cheaper to build (one codebase) and faster to distribute (no app store review), but they trade away deeper OS integration and predictable performance for that. The right answer depends on what the app needs to do.
Can a PWA work fully offline?
Yes, with a service worker that pre-caches the app shell and a data layer that uses IndexedDB or the Cache API to store user data. The PWA must explicitly handle conflict resolution when reconnecting.