Module 4: Advanced web technologies

4.2 Introduction to Progressive Web Apps

Progressive Web Apps (PWAs) are user experiences that have the reach of the web, and are:

  • Reliable: Load instantly and never show the downasaur, even in uncertain network conditions.
  • Fast: Respond quickly to user interactions with silky smooth animations and don't use poor quality scrolling.
  • Engaging: Feel like a natural app on the device, with an immersive user experience.

This new level of quality allows Progressive Web Apps to earn a place on the user's home screen.


When launched from the user’s home screen, service workers enable a Progressive Web App to load instantly, regardless of the network state.


A service worker is like a client-side proxy, written in JavaScript and puts you in control of the cache and how to respond to resource requests. By pre-caching key resources you can eliminate the dependence on the network, ensuring an instant and reliable experience for your users.


53% of users will abandon a site if it takes longer than 3 seconds to load! And once loaded, they expect them to be fast, no janky scrolling or slow to respond interfaces.


Progressive Web Apps are installable and live on the users home screen, without the need for an app store. They offer an immersive full screen experience with help from a web app manifest file and can even re-engage users with web push notifications.


The Web App Manifest allows you to control how your app appears and how it's launched. You can specify icons for the home screen and splash screen which is shown while the app is loading. You can also specify the page that's loaded when the app is launched, the screen orientation, and even whether to show the browser chrome or not.

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