A Progressive Web App is a web application that uses modern browser capabilities to deliver an experience indistinguishable from native mobile apps. PWAs can be installed on home screens, work offline, send push notifications, and access device hardware, all without app store distribution or platform-specific code.
How It Works
Three technologies make PWAs possible. A Service Worker is a JavaScript file that runs in the background, intercepting network requests and caching resources for offline use. A Web App Manifest is a JSON file describing the app's name, icons, theme color, and display mode. HTTPS is required because service workers have powerful capabilities that demand a secure context.
When a user visits a PWA multiple times, the browser offers an "Add to Home Screen" prompt. Once installed, the app launches in its own window without browser chrome, loads instantly from cached assets, and handles network failures gracefully by serving cached content.
Why It Matters
PWAs eliminate the friction of app store installation. Users do not need to find your app in a store, download 50MB, wait for installation, and create an account. They visit your URL and start using it immediately. Installation happens after they have already experienced value.
For businesses, PWAs mean one codebase serving all platforms. Development costs drop, updates ship instantly without store review processes, and you avoid the 15-30% revenue cut that app stores charge. Twitter Lite (a PWA) saw a 75% increase in tweets sent and a 20% decrease in bounce rate compared to their native app.
In Practice
Starbucks built a PWA that is 99.84% smaller than their iOS app. It works offline so customers can browse the menu without connectivity, adds items to their order, and submits when connection returns. The result: doubled daily active users from web.
Pro Tips
Start with a caching strategy. Cache-first works for static assets, network-first for API data. Use Workbox to simplify service worker logic. Test offline behavior with Chrome DevTools' network throttling. Remember that iOS Safari has PWA limitations, so test thoroughly on Apple devices.