Progressive Web App (PWA) Development for Mobile

Often clients approach us with a request for a mobile presence without publishing to the App Store and Google Play. Or they already have a website on React/Vue/Angular and need to add offline mode, push notifications, and a home screen icon — without rewriting everything from scratch. A real PWA requires a Service Worker with the correct caching strategy, a Web App Manifest with proper parameters for each platform, and HTTPS without exceptions. Skip any of these three components, and you get an app that doesn't install or works incorrectly offline. Request an assessment of your project in 1 day — contact us.

Where does PWA typically break?

Service Worker and caching strategies

The most common mistake is caching everything with CacheFirst without invalidation. The user opens an updated app but sees the old version because sw.js serves resources from an outdated cache. Workbox solves this by using StaleWhileRevalidate for static assets and NetworkFirst for API requests, but you need to clearly separate what to cache aggressively (fonts, icons, JS bundles with hashes) and what to always fetch fresh (user data, inventory, content).

Another issue is background synchronization via the Background Sync API. A user submits a form offline, the Service Worker intercepts the request and stores it in SyncManager. When connectivity is restored, the request is sent. It sounds simple, but registration.sync.register('sync-orders') only works on Chrome/Android. On iOS Safari, Background Sync is still not supported — this must be considered when designing offline scenarios. For example, an alternative could be manual data sending when the connection is restored.

What limitations exist on iOS?

Apple has been systematically limiting PWAs: until version 16.4, push notifications in PWAs did not work at all. They now work, but only if the app is added to the home screen via Safari — not from Chrome, not from Firefox. The default IndexedDB storage quota on iOS is 50 MB, compared to gigabytes on Android. Cacheable resources need to be calculated in advance. If you plan push notifications, be sure to use VAPID keys and note that on iOS, installation via Safari is required.

Why is PWA better than native for some scenarios?

PWA development is 3–5 times faster than a native app and costs 2–3 times less. Updates happen automatically, without store reviews. For informational portals, news sites, and corporate services, PWA often proves more efficient: it takes up less space on the device, does not require installation from a store, and the conversion to installation (via beforeinstallprompt) can reach 60%. However, for apps with deep system integration (camera, Bluetooth, NFC), a native app remains the only option.

How we build PWAs: step-by-step

1. Audit — check HTTPS, Core Web Vitals, and the current Service Worker (if any).
2. Configuration — we use Workbox 7.x via vite-plugin-pwa. The generateSW mode automatically creates a precache manifest from the bundle.
3. Manifest — name, short_name, start_url with the parameter ?source=pwa, display: standalone, theme_color, background_color, icons 192×192 and 512×512, plus a maskable variant for Android.
4. Service Worker — configure strategies: StaleWhileRevalidate for static assets, NetworkFirst for APIs, CacheFirst for immutable resources.
5. Push notifications — register VAPID keys, subscribe via PushManager.subscribe().
6. Testing — debug with Lighthouse, Chrome DevTools (Application → Service Workers → Offline) and on real devices.

How to achieve high installation conversion?

Chrome shows the "Add to Home Screen" banner when criteria are met: HTTPS, a valid manifest, and a registered Service Worker with a fetch handler. Lighthouse checks all conditions. For independent control, we use the beforeinstallprompt event: intercept it via event.preventDefault(), defer it, and show our own UI at the right moment, then call prompt(). This gives us control over when and to whom to offer installation. On iOS, installation is only manual via Share → "Add to Home Screen" — no automatic prompts.

Push notifications via the Web Push Protocol

VAPID keys are generated once, the public key is passed to the client when subscribing via PushManager.subscribe(). On the server, we use the web-push library for Node.js or an equivalent. The subscription object with endpoint, p256dh, and auth is saved in the database — this is what is needed for sending.

// Subscription registration
const subscription = await registration.pushManager.subscribe({
  userVisibleOnly: true,
  applicationServerKey: urlBase64ToUint8Array(PUBLIC_VAPID_KEY)
});

Comparison of PWA and native apps

What is included in the work

During the audit phase, we check performance (Core Web Vitals), HTTPS configuration, and the current Service Worker if any. Then we develop a Service Worker with caching strategies for specific routes, create a manifest, icons of all sizes, and splash screens for iOS. If push notifications are needed, we set up Web Push and test offline scenarios in Chrome DevTools and on real devices. On average, adding PWA to an existing site takes 3–7 days, and full development from scratch takes 2–4 weeks.

The result is verified using the Lighthouse PWA audit — all items must be green. We have been working on PWAs for over five years, and every project undergoes such testing. Our experience includes integration with Firebase and Supabase for push notifications and background synchronization.

Typical mistakes when implementing PWA:

• Ignoring cache invalidation — users see outdated content.
• Missing maskable icon — on Android, the icon appears with a white background.
• Push notifications without checking iOS support.
• Using only CacheFirst for APIs — loss of data freshness.

Timelines

Adding PWA to an existing web application: 3–7 days. Developing a PWA from scratch with offline logic and push notifications: 2–4 weeks. The cost is calculated after analyzing the current stack and requirements for offline functionality. We will assess your project in 1 day — contact us for a consultation.

How to choose cross-platform development: Flutter, React Native, or KMM?

We often work with startups that need two apps—iOS and Android—with a budget for one team. Or corporations that want to release an internal tool in three months on both platforms. Cross-platform development solves a specific economic problem: one codebase instead of two. The question is not 'cross-platform or native'—it's 'which tool for which task.'

Each framework dictates its own stack and imposes limitations. An incorrect choice leads to rewriting the project in six months—we've seen it many times with clients who came to us after a failed first attempt. Therefore, before starting, we conduct an audit of technical requirements and team expertise. With 8+ years of cross-platform experience and 50+ delivered apps, we know the pitfalls firsthand.

The three main players now: Flutter, React Native, and Kotlin Multiplatform Mobile. They solve different problems and are poorly compared head-on. Below, we'll break down how to choose the best option for your project.

How do we choose the technology? 4 steps

1. Requirements analysis — list of native APIs, need for offline work, branded UI or standard.
2. Team assessment — expertise in Dart, JavaScript/Kotlin, availability of an iOS developer.
3. Proof-of-concept — implement a critical scenario on the chosen stack in 2–3 days.
4. Final decision — based on performance benchmarks and maintenance cost.

Case from our practice: a fintech startup needed an MVP on both platforms in 10 weeks. Their team had deep React experience, so we selected React Native. The app passed App Store and Google Play review on the first submission, and they launched on schedule. That choice saved 4 weeks compared to training for Flutter.

Comparison of Flutter and React Native: under the hood

Rendering model

Flutter renders UI independently via the Impeller engine (replaced Skia starting with version 3.10). The platform only provides a canvas—Flutter draws every pixel itself. This means:

• Pixel-perfect on all platforms. The same widget looks identical on iOS and Android—good for branded apps, bad if you need a 'native' look on each platform.
• No dependency on OS version. Material 3 in Flutter works the same on Android 8 and Android 14. System Android components are not involved.
• Platform channels for native code. Access to camera, Bluetooth, NFC—via MethodChannel or EventChannel. flutter_camera, flutter_blue_plus are wrappers over platform channels.

React Native uses native platform components. <View> on iOS is UIView. <Text> is UILabel. This means:

• Native look and feel without extra effort.
• New Architecture (Fabric + TurboModules) with JSI removed the JSON bridge between JS and native code. Synchronous calls work without serialization. This is critical for animations and gestures.
• React Native Reanimated 3 runs worklets on the UI thread—animations at 60/120 fps without blocking the JS thread.

Performance in practice

For most business apps, the performance difference between Flutter and React Native New Architecture is imperceptible. The difference appears in edge cases.

Flutter is slower when interacting with platform APIs via platform channels—each call is asynchronous, with data serialization overhead. google_maps_flutter renders the map via PlatformView—a native UIView/View embedded in the Flutter tree. Before Impeller, this caused performance issues (Hybrid Composition vs Virtual Display). With Impeller, Flutter renders UI 2–3x faster on low-end devices compared to Skia, and PlatformView performance improved by 40%.

React Native is slower in scenarios with heavy JS logic on the main thread. Parsing large JSON, complex computations—these block the JS thread and appear as UI freezes. Solution: Hermes (JS engine optimized for RN) + offloading computations to a native module or react-native-workers. With Hermes, cold start time is reduced by 30–40% compared to JavaScriptCore—that's 2x improvement on older devices.

Ecosystem and maturity

Dart is a barrier to entry for teams with a JS/TS background. It's possible to learn basic Dart in a week, but shifting your mindset to Flutter widgets and widget tree takes longer.

TypeScript in React Native is the de facto standard. A team with React experience becomes productive faster.

When to choose Flutter?

• Need a unified branded UI on all platforms (iOS, Android, Web, Desktop).
• Team is ready for Dart.
• Lots of custom animation and custom UI—Flutter is more predictable.
• The app is not tied to specific native APIs.

When to choose React Native?

• Team has React/TypeScript expertise.
• Need native look and feel.
• Heavy use of native components (Maps, Camera with native capabilities).
• Sharing code with React web via monorepo.

Kotlin Multiplatform Mobile: a different story

KMM solves not a UI problem, but the problem of business logic duplication. The concept: write business logic, networking, caching, validation once in Kotlin. iOS receives a .framework via Kotlin/Native, Android uses the library directly. UI on each platform is native.

// Shared Kotlin code — works on iOS and Android
class UserRepository(
    private val httpClient: HttpClient, // Ktor
    private val database: AppDatabase   // SQLDelight
) {
    suspend fun getUser(id: String): User {
        return database.userQueries.selectById(id).executeAsOneOrNull()
            ?: httpClient.get("$BASE_URL/users/$id").body<User>().also {
                database.userQueries.insert(it)
            }
    }
}

Ktor — HTTP client for KMM (works on iOS via Darwin engine, on Android via OkHttp). SQLDelight generates a typesafe Kotlin API for SQLite, works on both platforms.

Real limitations of KMM

Coroutines on iOS: suspend functions from shared code are called through automatically generated wrappers. SKIE (Swift/Kotlin Interface Enhancer) from Touchlab significantly improves the Swift interface: async/await instead of callbacks, AsyncStream for Flow. Without SKIE, working with coroutines from Swift is inconvenient.

Compose Multiplatform: JetBrains is developing Compose for iOS — UI in Compose works on iOS via Metal. This blurs the line with Flutter: one Compose code for both platforms. Status today: Beta, with early adopters in production (Touchlab, JetBrains own products), but stability is lower than Flutter.

Complexity of iOS integration: XCFramework from KMM module is added to an Xcode project. SPM integration exists and works. But iOS developers must understand the Kotlin API and memory management rules via Kotlin/Native (ARC + Kotlin GC work together, which is not always obvious).

When KMM is justified

The company already has mature iOS and Android teams that duplicate business logic. Switching everything to Flutter or React Native is too radical. KMM allows starting small: extract networking and models into shared code, keep UI native. Gradual migration without rewriting everything.

Typical mistakes in technology selection

Choosing Flutter "because it's a single codebase" for an app heavily reliant on native APIs (custom camera, BLE, background processing). Implementing these via platform channels adds complexity that eats up the development speed advantage.

React Native without understanding the JS thread. Heavy operations on the JS thread cause visible freezes. This is solvable, but requires understanding the architecture—otherwise the app will perform worse than native.

KMM without an iOS developer on the team. Shared Kotlin code requires an iOS engineer who integrates the framework into Xcode, writes SwiftUI on top of KMM APIs, and debugs Kotlin/Native crashes.

What is the development process and timeline?

A cross-platform project goes through the same stages as a native one: requirements audit → stack selection → design → development → testing on real devices of both platforms → publication in App Store and Google Play → support.

Testing on real devices is not optional. An emulator does not reproduce memory issues on budget Android phones and does not show differences in gesture behavior on iOS. We test 40+ scenarios on at least 5 real devices covering both OS versions.

Budget savings compared to two native teams can be up to 40–50%. The cost is calculated individually after analyzing the stack and requirements.

What's included in our work

• Technical audit and stack selection for your project.
• Architecture design (clean architecture, MVVM, BLoC/Redux).
• UI development according to design mockups for both platforms.
• Integration of native modules (camera, geolocation, push notifications).
• CI/CD setup (GitHub Actions, Codemagic).
• Testing on real devices (iOS/Android) — at least 40 scenarios.
• Preparation and publication in App Store and Google Play following guidelines (App Store Review, Google Play Policy).
• Technical support for 3 months after launch.
• Handover of source code, documentation, and access — all turnkey.

We'll evaluate your project in one day—get a consultation on stack selection. Order turnkey development and receive a cross-platform app within the agreed timeline, backed by our experience and guaranteed milestones.