Progressive Web App Implementation: Building Apps That Work Offline and Install Like Native
A PWA is not a compromise between web and native. It is a web application that does the things users expect from native: installs, works offline, and sends push notifications.
A Progressive Web App is a web application that uses service workers, a web app manifest, and modern web APIs to deliver an experience that feels native: it can be installed on the home screen, it works offline, it sends push notifications, and it accesses device hardware. The technology is mature and the browser support is broad — but the implementation details matter.
The three components of a PWA
1. Web App Manifest
A JSON file that tells the browser how to install the app: name, icons, theme colour, display mode (standalone, fullscreen), and start URL. Without a manifest, the app cannot be installed. The manifest is simple but it must be correct — incorrect icons or display modes produce an installation experience that feels broken.
2. Service Worker
The service worker is the core of a PWA. It is a JavaScript file that runs in the background, intercepts network requests, and decides how to respond — from cache, from network, or a combination. This is what enables offline functionality, background sync, and push notifications. The service worker is also the most complex part to implement correctly because caching strategies require thought.
3. HTTPS
Service workers require HTTPS. This is not optional and not negotiable — service workers intercept network requests, and allowing them over HTTP would be a security vulnerability. If your site is not on HTTPS, you cannot build a PWA. This is rarely a problem in 2026, but it is worth noting.
Caching strategies: the part that requires thought
| Strategy | When to use | How it works |
|---|---|---|
| Cache First | Static assets (CSS, JS, images, fonts) | Serve from cache; fall back to network only if not cached |
| Network First | Dynamic content (API responses, HTML) | Try network; fall back to cache if offline |
| Stale While Revalidate | Content that updates but is not critical | Serve from cache immediately; update cache from network in background |
| Network Only | Non-cacheable content (analytics, POST requests) | Always use network; fail if offline |
The strategy you choose per resource type determines the offline experience. A cache-first strategy on HTML means users see stale content. A network-first strategy on images means they do not load offline. Match the strategy to the content type and the user expectation.
The iOS reality
iOS supports PWAs but with limitations that Android does not have. Push notifications support arrived later and is more restricted. Background sync is limited. The installation experience is different. Test on iOS specifically — do not assume that because your PWA works perfectly on Android, it will work the same way on iOS. For many applications, the differences are manageable. For some, they are a reason to also build a native app.
Building PWAs that users actually install
A PWA is worth building when your users need offline access, installation, or push notifications — and when you want one codebase that serves web and mobile. We build PWAs with correct service worker strategies and iOS-tested implementations.
Kinematic Digital designs mobile security programmes for enterprise organisations. See our cybersecurity services and web development practice, or book a mobile security assessment.
Frequently Asked Questions
What is a Progressive Web App?
A web application that uses modern web APIs — service workers, web app manifest, push notifications — to deliver an app-like experience: installable, offline-capable, and responsive. PWAs run in the browser but can be installed on the user's device like a native app.
Can a PWA replace a native app?
For many use cases, yes. PWAs work offline, send push notifications, access device hardware (camera, GPS), and install on the home screen. They are not suitable for apps that require deep OS integration or app store distribution, but for content, commerce, and productivity apps, they are often sufficient.
Do PWAs work on iOS?
Yes, but with limitations. iOS supports PWA installation and some offline capability, but background sync and push notifications have historically been more restricted than on Android. Test on iOS specifically — do not assume Android behaviour applies.
What is a service worker?
A JavaScript file that runs in the background, separate from the web page. It intercepts network requests, enabling offline caching, background sync, and push notifications. The service worker is the technology that makes a PWA feel like an app rather than a website.
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