PWA definition
A Progressive Web App (PWA) is a website built with modern web APIs so it behaves like an installed app. It can be added to a home screen, open in its own window, work offline through a service worker and send push notifications, while still being delivered from a URL without an app store download.
How does a PWA work?
A PWA is a normal website served over HTTPS with two extra pieces. A web app manifest, a small JSON file, tells the browser the app's name, icons, theme color and how it should open when installed. A service worker, a script that runs in the background separate from the page, intercepts network requests and can serve cached responses, which is what makes offline use and instant repeat loads possible. The service worker also receives push messages and can sync data once connectivity returns.
- HTTPS: required for service workers and installation
- Web app manifest: name, icons, start URL and display mode
- Service worker: caching, offline support, background sync and push
- Responsive design so the same app works on phones, tablets and desktops
PWA vs native app
A PWA has one codebase, no app store review and instant updates on the next visit, which makes it cheaper to build and maintain than separate iOS and Android apps. It is also discoverable through search. The limits show on iOS, where Safari supports fewer device APIs and storage can be cleared more aggressively. Features like deep Bluetooth access, background location, widgets and some payment flows still need a native or cross-platform app.
Examples of progressive web apps
Large consumer brands have used PWAs to reach users on low-end devices and slow networks. Twitter Lite, Starbucks ordering, Pinterest's mobile web and Uber's lightweight web client are frequently cited examples. Productivity tools such as Google Docs and Figma use PWA features for installation and offline behavior on desktop. In emerging markets, PWAs are popular because a small download and low data use matter more than access to every hardware feature.
How to build a PWA
Caching is where most PWA bugs live. An aggressive cache can serve yesterday's prices or keep users on an old version long after a release, so plan how the service worker updates itself and test what users actually see after each deploy.
- Serve the site over HTTPS and make every page responsive
- Add a web app manifest with name, icons, theme color and display mode
- Register a service worker, usually generated with a library such as Workbox
- Choose caching per route: cache-first for static assets, network-first for prices and stock
- Provide an offline fallback page and queue form submissions for background sync
- Audit installability and performance with Lighthouse in Chrome DevTools
- Test install and offline behavior on real Android and iOS devices
When should you build a PWA?
A PWA is a strong choice for content sites, e-commerce, booking flows, internal business tools and any product where reach and fast iteration matter more than deep hardware integration. It also works well as a first release that validates demand before investing in native apps. Nexzem builds PWAs with Next.js and Workbox, planning caching strategies per route so that offline support helps users instead of serving stale prices or inventory.