What defines a Progressive Web App

A Progressive Web App (PWA) is a web application that uses modern APIs to deliver enhanced capabilities while remaining accessible to every web user across devices through a single codebase. PWAs sit at the intersection of the broad reach of the web and the rich functionality normally associated with platform-specific applications.

The three pillars of PWA design

Building a PWA that rivals a native experience means paying attention to three foundational design principles: capability, reliability, and installability.

Capability

The line between what the web can do and what was once exclusive to native apps continues to blur. Developers can already build hyper-local video chat apps using WebRTC, geolocation, and push notifications, then take it further by making the app installable and adding WebGL and WebVR for immersive virtual reality conversations. WebAssembly opens the door to ecosystems like C, C++, and Rust, bringing years of previously platform-specific code to the web. Squoosh.app is a prime example of a web-based tool that leverages these expanded abilities.

Areas that remain out of reach are shrinking as new APIs emerge for file system access, media controls, app badging, and full clipboard support. All of these capabilities are built on the web's secure, user-centric permission model, which keeps users in control and reduces the intimidation factor of trying new sites.

Reliability

A reliable PWA feels fast and predictable no matter the network conditions. Users expect snappy responses to interactions, and they quickly abandon experiences that don't deliver. The stakes are high: extending page load time from one second to ten seconds raises the probability of a user bouncing by 123%. Performance issues touch the entire experience, not just the onload event. Scrolling, animation, and every interaction need to feel smooth, and the app must give users the perception of good performance, not just deliver it under the hood.

Reliability also extends to offline and degraded network scenarios. Users expect apps to load quickly on flaky connections, and they expect their most recent content, be it media files, tickets, or itineraries, to remain available even when the server isn't reachable. When a request cannot be made, the app should clearly communicate the problem rather than fail silently or crash.

Installability

An installed PWA escapes the browser and runs in its own standalone window, changing how users perceive and interact with it. Users can launch it from their home screen, dock, taskbar, or shelf, and it integrates with the device's app switcher and search. This placement makes the PWA feel like a first-class resident of the device.

Installation unlocks new capabilities as well. Keyboard shortcuts, which browsers typically reserve for themselves, become available, and PWAs can register to handle content from other applications or act as the default app for specific file types.

Business impact of PWAs

Deploying a PWA isn't just a technical upgrade; it has measurable effects on user engagement and service value. Several prominent companies have documented significant gains:

  • Twitter's PWA delivered a 65% increase in pages per session, 75% more Tweets, and a 20% drop in bounce rate, while slashing app size by over 97%.
  • Nikkei reported 2.3 times more organic traffic, 58% more subscriptions, and 49% more daily active users after moving to a PWA.
  • Hulu swapped its platform-specific desktop app for a PWA and saw a 27% rise in return visits.