progressive-web-app

# Progressive Web Apps (PWAs) ## Overview A Progressive Web App is a web application that uses modern browser capabilities to deliver a fast, reliable, and installable experience — even on unreliable networks. The three required pillars are: 1. **HTTPS** — Required in production for service workers to register (localhost is exempt for development). 2. **Web App Manifest** (`manifest.json`) — Makes the app installable and defines its appearance on device home screens. 3. **Service Worker** (`sw.js`) — A background script that intercepts network requests, manages caches, and enables offline functionality. ## When to Use This Skill - Use when the user wants their web app to work offline or on unreliable networks. - Use when building a mobile-first web project where users should be able to install the app to their home screen. - Use when the user asks about caching strategies, service workers, or improving web app performance and resilience. - Use when the user mentions Workbox, web app manifests, background sync, or push notifications for the web. - Use when the user asks "can my website be installed like an app?" or "how do I make my site work offline?" — even if they don't use the word PWA. ## Deliverables Checklist Every PWA implementation must include these files at minimum: - [ ] `index.html` — Links manifest, registers service worker - [ ] `manifest.json` — Full app metadata and icon set - [ ] `sw.js` — Service worker with install, activate, and fetch handlers - [ ...