Progressive web apps (PWAs) are web applications that are reliable, fast and engaging. They load instantly, never show down time, and work across all browsers. PWAs provide an app-like experience to users through features like being installable on home screens, working offline, and with fast loading speeds even on slow mobile networks. Examples that demonstrate the benefits of PWAs include increased user engagement metrics for Twitter Lite and AliExpress, with higher conversion rates, more time spent per session, and more pages viewed per user session.