PWA in Practice: Installable, Offline-Ready Tool Sites

What Is a PWA?

A PWA (Progressive Web App) gives web apps an experience close to native apps:

Capability	Traditional Web	PWA
Install to home screen	❌	✅ Add to Home Screen
Offline access	❌	✅ Service Worker cache
Push notifications	❌	✅ Push API
Full-screen	❌	✅ standalone mode
Auto updates	✅	✅ background SW updates

For high-frequency tool sites like ToolsKu, a PWA means users can open PDF merge, JSON formatters, and other favorites in one tap—like a native app.

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Web App Manifest

manifest.json defines install metadata:

{
  "name": "ToolsKu - Online Tools Collection",
  "short_name": "ToolsKu",
  "start_url": "/en/",
  "display": "standalone",
  "background_color": "#ffffff",
  "theme_color": "#2563eb",
  "icons": [
    { "src": "/icons/icon-192.png", "sizes": "192x192", "type": "image/png" },
    { "src": "/icons/icon-512.png", "sizes": "512x512", "type": "image/png" }
  ]
}

Field	Role
display: standalone	Hides the browser address bar
start_url	Page opened after install
theme_color	Status/title bar color
icons	Home screen icons (at least 192px and 512px)

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Service Worker Caching Strategies

Cache first (static tool assets)

// Good for: JS/CSS/WASM/fonts that rarely change
self.addEventListener('fetch', (event) => {
  event.respondWith(
    caches.match(event.request).then(cached => {
      return cached || fetch(event.request).then(response => {
        const clone = response.clone();
        caches.open('static-v1').then(cache => cache.put(event.request, clone));
        return response;
      });
    })
  );
});

Network first (HTML pages)

// Good for: HTML that may update
event.respondWith(
  fetch(event.request).catch(() => caches.match(event.request))
);

ToolsKu cache tiers

Resource	Strategy	TTL
_next/static/**	Cache First	1 year (hash filenames)
*.wasm	Cache First	1 year
*.html	Network First	1 hour
i18n JSON	Stale While Revalidate	1 day

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Offline Tool UX

UX design when the PWA is offline:

User opens ToolsKu offline
     ↓
Service Worker returns cached HTML/JS/CSS
     ↓
Tool page loads (SSG pre-rendered HTML)
     ↓
Client Component starts; tool logic runs locally
     ↓
File API / WASM processes files → fully offline

All core ToolsKu tools (PDF, images, JSON, crypto) use browser-local APIs and work offline by nature—the PWA only needs to cache static assets.

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Install Prompt Best Practices

let deferredPrompt: BeforeInstallPromptEvent;

window.addEventListener('beforeinstallprompt', (e) => {
  e.preventDefault();
  deferredPrompt = e;
  showInstallBanner(); // custom install UI
});

installButton.addEventListener('click', async () => {
  deferredPrompt.prompt();
  const { outcome } = await deferredPrompt.userChoice;
  if (outcome === 'accepted') hideInstallBanner();
});

Tip: Don’t show the install prompt too early. After the user successfully uses 2–3 tools, conversion rates are higher.

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Summary

PWAs are an effective way to improve retention on tool sites. Web App Manifest provides the install entry; Service Worker enables offline caching; and ToolsKu’s browser-local processing architecture makes offline tools feel the same as online.