Answer

Do PWAs support background sync?

Short answer

Partially. Chromium browsers (Chrome, Edge, Android WebView, Samsung Internet) support the Background Sync API for retrying failed requests, and Periodic Background Sync for scheduled updates. iOS Safari and Firefox do not support either. Fall back to Push notifications for cross-platform re-engagement.

By InstantPWA engineering·Reviewed July 22, 2026

One-shot Background Sync

Register a sync tag when a request fails. The browser retries it once connectivity returns, even if the tab is closed. Widely supported on Chromium.

Periodic Background Sync

Runs a task at roughly daily intervals. Chrome only, requires a "high site engagement" score, and users can disable it in browser settings.

The iOS workaround

iOS Safari does not implement either API. Use silent Web Push (via Notification.showNotification with silent: false is required) to wake the SW and refresh caches.

Sources

Can a PWA send push notifications on iOS?

Yes. Since iOS 16.4 (March 2023), a PWA can send Web Push notifications on iPhone and iPad — but only after the user installs it to the home screen. Push in a regular Safari tab is not supported, and the user must explicitly grant notification permission from inside the installed PWA.

Do PWAs work offline?

PWAs can work offline, but only for content their service worker has explicitly cached. Registering a service worker does not automatically make a site offline-capable — you decide what to cache (app shell, API responses, images) and what strategy to use (cache-first, network-first, stale-while-revalidate).

PWA vs hybrid app — what is the difference?

A PWA is a website users install from the browser — no store, no shell, no native code. A hybrid app (Ionic + Capacitor, Cordova, older React Native WebView apps) wraps the same web code in a native binary submitted to the App Store and Play Store. PWAs are cheaper and faster to ship. Hybrid apps unlock store distribution and deeper hardware APIs.

Do PWAs improve conversion rate?

Yes, when users actually install. Published case studies (Alibaba, Twitter Lite, Pinterest, Uber, BookMyShow) show 30-100% conversion lift after PWA adoption — driven by faster loads, offline support and home-screen install. The effect is largely from install: once your icon sits on the home screen, return sessions jump.

Can PWAs read and write files?

Yes on Chromium browsers (Chrome, Edge, Opera). The File System Access API lets a PWA open, read, edit and save files with the user’s permission — Figma, VS Code Web and Excalidraw use it in production. iOS Safari and Firefox fall back to the standard `<input type="file">` and downloads.