What is a Progressive Web App? How do progressive web apps work?

Designer Frances Berriman and engineer Alex Russell built the first progressive app in 2015. A recent survey carried out by Comscore indicates that 50% of smartphone users in the US alone don’t download a single app a month. Progressive web apps have been built to address this issue.

Progessive apps, in general, can offer the experience of native apps on several mobile web browsers such as Opera, Chrome, etc. Progressive web apps can be hosted on user’s server and can be updated easily minus the need of issuing new updates to an app store or play store. These web apps are built with native app-like capabilities including quick loading, background refresh, offline working and instability.

So, how do progressive web apps work?

The core concept behind progressive web apps is Service Worker, a technology that is highly robust and powerful. They come with several features including content caching, functionality, background content updating and push notifications.

A worker script, Service worker, runs on the background in response to push notifications, connecting changes, network requests and more. A service worker, though incomprehensible and compelling for many developers, functions as a middleware or proxy for this requests type. With an array of features, web developers can have a tough time understanding how Service Workers actually work.

These are similar to other Javascript file where the developer has to develop code for various events like content fetching, catching and push notifications. Service Workers, at present, are available on Android with Chrome 50 and not on other browsers.

App shell, a design concept that allows the app shell to load first, and subsequently the content, is another technology used. Content and Design are cached separately for the improvement of the usability and performance of the app. Also, Chrome on Android offers app manifest i.e., support for web apps that allows you to install on the home screen using a native install banner. This feature is present in Progressive web apps.

Coders usually write a manifest.json file which is linked to the main HTML page so that the progressive web app can be installed like an app. Android can easily support progressive web apps. iOS is still not progressive-web-app-friendly as it is bound by strict policies and rules; therefore, it will take some time.