Progressive Web Apps (PWA) Overview, Service Worker Fundamentals, and iQiyi PC Implementation

Progressive Web Apps (PWA) are web applications that can work offline, be installed as standalone apps, and provide a native‑like experience across platforms.

The concept was introduced by the Chrome team in 2015. PWA combines the lightweight, cross‑platform nature of web apps with features traditionally found in native apps, such as installation, offline capability, system integration, and high performance.

Key characteristics required for a PWA include: running on any device, fast launch and installability, desktop shortcut support, independent windows, offline operation, system‑function integration, and good performance.

Compared with native apps, web apps still lag in UI quality, icon‑based entry, and deep system integration, which PWA aims to bridge by allowing installation to the desktop and access to system APIs.

PWA’s three main qualities are reliability, speed, and immersive experience. These are achieved through a set of modern web technologies, most notably Service Workers and a manifest.json file.

Service Worker is a background script that runs independently of the page, intercepts network requests, provides caching, push notifications, and background sync. Its lifecycle consists of registration, installation, activation, and updates. Because it runs on a separate thread, it does not block the main UI thread.

The manifest.json file defines the app’s name, icons, start URL, display mode, and other metadata, enabling the browser to present the app as installable.

Installation of a PWA requires HTTPS (or localhost for development), a registered Service Worker with a fetch handler, and a valid manifest containing fields such as short_name/name, icons (192 px and 512 px), start_url, and a display mode of fullscreen, standalone, or minimal‑ui. When these conditions are met, Chrome fires the beforeinstallprompt event, which can be used to show a custom install prompt.

The article presents a concrete case study of iQiyi’s PC PWA. Service Workers are used to cache CSS, JavaScript, and image assets on the login page, dramatically reducing response start time and stabilizing page‑load performance. Screenshots show the reduced network latency and the installation UI that appears in the bottom‑right corner of the iQiyi homepage.

Additional optimizations include handling click navigation within a single‑page PWA, recording the last opened URL to restore the user’s session, and strategies for balancing fast display with cache freshness and cross‑origin resource caching.

After launch, iQiyi’s PWA increased user retention by 9% compared with the regular web site. Future work will explore offline work, push messaging, theming, and behavior‑driven UI adjustments.