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Progressive Web Apps: Offline-First Architecture (2025)

Oct 26, 2025•
pwaoffline-firstservice-workerperformance
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PWAs deliver app-like reliability on the web. This guide details offline-first patterns with service workers and resilient UX.

Executive summary

  • Cache shell + critical data; background sync; conflict resolution for offline edits
  • Respect storage limits and eviction; hint users about sync state
  • Secure origins (HTTPS), correct scopes, and update strategies

Service worker basics

self.addEventListener('install', (e) => {
  e.waitUntil(caches.open('app-shell').then(c => c.addAll(['/','/styles.css','/app.js'])))
})
self.addEventListener('fetch', (e) => {
  e.respondWith(caches.match(e.request).then(r => r || fetch(e.request)))
})

Caching strategies

  • Cache-first, network-first, stale-while-revalidate; per-route choices

Sync and conflicts

  • Background Sync for retries; local queue; CRDTs for collaborative edits

Push and notifications

  • Permissions UX; actionable notifications; privacy considerations

UX patterns

  • Offline banners; optimistic UI; retry indicators; version update prompts

FAQ

Q: Are PWAs allowed on iOS?
A: Yes, with limitations that have improved; test capabilities per iOS version.

  • Core Web Vitals: /blog/web-performance-optimization-core-web-vitals-2025
  • RSC Next.js: /blog/react-server-components-complete-guide-nextjs-14-15
  • React Patterns: /blog/react-design-patterns-hooks-context-state-management
  • Frontend Testing: /blog/frontend-testing-strategy-jest-cypress-playwright-2025
  • Micro‑Frontends: /blog/micro-frontends-architecture-module-federation-2025

Call to action

Shipping a PWA? Get an offline‑first readiness review.
Contact: /contact • Newsletter: /newsletter

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