PWA Development: Offline-First Progressive Web Apps

Not just "a website that works offline". It is a caching architecture with invalidation strategies, background sync, and lifecycle management. TTI under 3s on 3G, app experience without App Store.

Design PWA Architecture See Methodology
  • <3s TTI on 3G
How we build: requirements, architecture, reviewed code, reversible deployment, measured performance and evolution with your team Every metric sets the next iteration 01 · Requirements What the businessneeds 02 · Architecture Documenteddecisions 03 · Code Reviewed andtested 04 · Deployment Automated andreversible 05 · Performance Core Web Vitals inthe green 06 · Evolution Your team asks, wedeliver
  1. 01 · Requirements What the business needs
  2. 02 · Architecture Documented decisions
  3. 03 · Code Reviewed and tested
  4. 04 · Deployment Automated and reversible
  5. 05 · Performance Core Web Vitals in the green
  6. 06 · Evolution Your team asks, we deliver
  7. Every metric sets the next iteration
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In numbers

Proven Results

Metrics that define a professional PWA.

  • 15+ Years of Experience Web development since 2009
  • 95+ PWA Score Lighthouse certified
  • Offline Critical Flows Works without network

What's included

Service Deliverables

What you receive. No ambiguity.

  • Offline-readiness audit and caching strategy
  • Service Worker with Workbox configured for your case
  • App Shell pattern for instant loading
  • Optimized Web App Manifest for installation
  • Push notifications (if applicable) with FCM or similar
  • CI pipeline with automated Lighthouse audits

Why

Traditional Web vs Kiwop PWA

The problem with the websites you know.

Traditional web: every request goes to the internet, no connection means nothing, slow mobile loading, not installable. Kiwop PWA: Service Worker as intelligent proxy, you decide what to serve from cache, what goes to network, what to show as fallback. Users see UI in under 100ms even offline. The perception: "this app responds instantly".

sw.js
// Service Worker Caching Strategy
self.addEventListener('fetch', (event) => {
event.respondWith(
caches.match(event.request)
.then(cached => cached ||
fetch(event.request)
)
);
});
  • <100ms Shell
  • ✓ Offline
  • 95+ PWA Score

Definition

What Is a PWA and Why Does It Matter in 2026?

A Progressive Web App (PWA) is a web application that uses modern technologies (Service Workers, Web App Manifest) to deliver a native app experience from the browser: installable, offline, push notifications, instant loading.

In 2026, PWAs are the real alternative to native development for many use cases. Advantages: single codebase for web and "app", no App Store costs (30% commission), instant updates without going through review, shareable URL. The Service Worker is the core: a programmable proxy that intercepts requests and decides whether to serve from cache, go to network, or show fallback.

What's included

Executive Summary

What you need to know to decide.

  • 50-70% savings vs dual native development (iOS + Android)
  • No App Store commissions (30%) or review process
  • Instant updates without waiting for approval
  • Shareable URL, indexable by Google, SEO maintained
  • Existing web conversion in weeks, not months
  • Main risk: limitations on iOS (storage, some APIs)

What's included

CTO / Technical Team Summary

Architecture and implementation requirements.

  • Service Workers mandatory (HTTPS required)
  • Workbox for caching strategy abstraction
  • App Shell pattern + content streaming
  • IndexedDB for complex offline persistence
  • Background Sync for resilient requests
  • Lighthouse CI in pipeline to maintain 95+ score

Who it is for

Is This for You?

PWA works if your audience does not need the App Store. If store discovery is critical, consider native.

Who it's for

  • Companies wanting app experience without dual native development.
  • Businesses with mobile users who do not want to download apps from stores.
  • Projects where offline or low connectivity is relevant.
  • Organizations with existing web wanting to improve mobile experience.
  • Teams with web expertise wanting to reuse knowledge (React, Vue).

Who it's not for

  • Apps requiring deep hardware access (Bluetooth LE, NFC, sensors).
  • Projects where App Store/Play Store presence is critical for discovery.
  • Experiences requiring intensive native performance (gaming, AR).
  • If your audience uses iOS and expects full native app experience.
  • Simple websites that do not benefit from offline functionality.

Key points

Caching Strategies We Implement

Workbox patterns for each use case.

  1. 01

    Stale-While-Revalidate

    Serves from cache immediately, updates in background. Ideal for assets that change little but need eventual freshness: blog posts, product images.

  2. 02

    Cache-First + Expiration

    Cache with defined TTL. For static assets: fonts, icons, versioned JS/CSS. Reduces requests, guarantees consistency with max-age.

  3. 03

    Network-First + Fallback

    Tries network, falls back to cache if offline. For data that must be fresh: prices, inventory. Fallback shows stale but functional data.

  4. 04

    Background Sync + Queue

    Failing requests are queued and retried when connected. For forms, uploads, critical actions. Real resilience.

How we work

Work Process

From traditional web to offline-first.

  1. 01

    Audit and Strategy

    Critical path analysis. What must work offline? What data needs sync? Caching strategy design by resource type.

    Week 1
  2. 02

    Service Worker Architecture

    Workbox configuration. App shell precaching. Runtime caching strategies. Lifecycle handling for updates.

    Week 2-3
  3. 03

    Offline UI/UX

    Visible connection states. Fallback pages. Queue indicators for pending actions. Edge case testing.

    Week 4
  4. 04

    Push and Installation

    Push notification setup (if applicable). Install prompt strategy. Optimized Web App Manifest. Lighthouse CI in pipeline.

    Week 5

Key points

Risks and How We Mitigate Them

Transparency about what can go wrong.

  1. 01

    iOS Limitations

    iOS has lower storage limits and some unavailable APIs. Mitigation: we design with iOS limitations as baseline, feature detection for extra capabilities on Android.

  2. 02

    Stale Cache (Obsolete Data)

    Aggressive caching can show old data. Mitigation: specific strategies per resource, cache versioning, UI indicating "last updated".

  3. 03

    Service Worker Updates

    Users can get stuck with old version. Mitigation: skipWaiting for critical updates, non-intrusive prompt for minor updates, maximum 2 reloads for new version.

  4. 04

    Debugging Complexity

    Service Workers add complexity layer. Mitigation: structured logging, documented DevTools workflow, caching tests in CI.

Technologies

Technology Stack

APIs and technologies for offline-first.

  • Service Workers
  • Workbox
  • CacheStorage API
  • IndexedDB
  • Background Sync
  • Periodic Sync
  • Push API
  • Web App Manifest
  • Vite PWA
  • next-pwa
  • Firebase Cloud Messaging
  • Lighthouse CI
  • Web Vitals

The proof

15 Years Building Web Experiences, Now Offline-First

Since 2009 we develop web applications that load fast and work well. PWAs are the natural evolution: the same web, but with superpowers. Installable, offline, notifications. No App Store, no commissions, no reviews.

  • 15+ Years of Experience
  • 200+ Web Projects
  • Client Retention 92%
  • Lighthouse PWA 95+

FAQ

Technical Questions

What CTOs and Product Managers ask.

Does PWA Work the Same on iOS as Android?

Not the same, but good enough for most cases. iOS supports Service Workers, offline, and installation since iOS 11.3. Push notifications since iOS 16.4. Limitations: lower storage limits, no badging API. For 90% of business apps, PWA on iOS is viable.

How Do You Handle Service Worker Updates?

SkipWaiting for critical updates, prompt for non-critical updates. We version assets with hashes. CacheStorage cleanup of old versions. Users always have the latest version after maximum 2 reloads.

PWA or Native App for My Case?

PWA if: content-heavy, e-commerce, utilities, you want to avoid app stores, your audience does not install apps. Native if: you need Bluetooth LE, intensive AR, complex background processing, your audience expects an app in store. For cross-platform native we offer Flutter development and React Native development.

Can I Convert My Existing SPA to PWA?

Yes. If it is already HTTPS and responsive, adding PWA capabilities is straightforward; if it is built with React, we use next-pwa or Vite PWA. The real work is designing what to cache, how to handle offline, and what background sync you need. Typically 2-4 weeks of development.

What Is the Typical Investment for a PWA?

Existing web conversion: €8,000-€15,000. New PWA with complex offline: €20,000-€35,000. Enterprise PWA with push, sync, and multi-tenant: €35,000+. Significantly less than dual native development (iOS + Android).

Are PWAs Indexed by Google Like Normal Websites?

Yes, PWAs are websites with superpowers. Google indexes them exactly the same. In fact, Google rewards PWAs with better Core Web Vitals (LCP, CLS) because they load faster thanks to caching.

What About Users Who Do Not Install the PWA?

It works perfectly as a normal website. Installation is optional and improves experience (fullscreen, home icon), but all caching and offline benefits work without installing.

Do You Work With International Companies?

Yes, we're a PWA development agency with 15+ years of experience. We work with clients across Europe and the Americas. Video conference meetings available.

Next step

Does Your Website Take More Than 5s to Load on 3G?

Offline-readiness audit. We analyze caching opportunities, measure TTI, and design PWA strategy. Report in 48h.

Request Audit
  • No commitment
  • Response in 24h
  • Custom proposal
Last updated: July 2026

Let's talk.

Initial technical consultation

AI, security and performance. Diagnosis with phased proposal.

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