A Guide to Progressive Web App Development

Mobile devices capture a majority of the web traffic today. People are relying more on their smartphones rather than desktop to carry out any task, and mobile apps play a pivotal role in it. Today’s generation looks for an app for every sort of activity. They find it troublesome to open the browser and enter the website they want to browse, repeatedly. Yes, native apps exist for this reason but not everyone has an app associated with their brand or enterprise. This is where a progressive web app or PWA comes as a perfect option for them to give users the convenience of a mobile app from a website.

Progressive web apps have proved to be a great alternative to traditional native apps; providing a similar kind of look and feel. PWAs use modern web capabilities to deliver an app-like experience. Like a native app, they can be installed on the user’s device and support features like push notifications. One of the best things about a PWA is that it supports offline functionality, which means it can be accessed even in areas with low or poor network connectivity. Businesses can build a PWA for their website and thus improve its usability and overall experience.

In this article about PWA development, we will learn how you can build a PWA or convert a web app into a progressive web app.

How to convert your website into a PWA?

Developers don’t need to rewrite the codes from scratch in order to build a PWA. A web app can be converted into a PWA by following the below steps-

1. The site must be HTTPS and not HTTP

A progressive web app can’t run on an HTTP server. You need to add an SSL certificate to your website in order to allow the PWA to use service workers and get installed on the home screen of the user’s device. Migrating from HTTP to HTTPS also adds an extra layer of security and trust to your website and protects it from insecure networks, phishing attacks, MiTM, and other data breaches. Simply purchase the SSL certificate from your domain registrar (some even provide it for free) and configure it with the help of your hosting provider.

2. Application shell

One way to build a PWA is through an app shell architecture that makes it possible for the PWA to load instantly when opened, similar to what you encounter in a native app. It is the minimal HTML, CSS, and JavaScript required to power the UI, which in turn provides an instant and consistently good performance upon recurring visits when cached offline. This means that the shell doesn’t load from the network on every visit but when the necessary content is required. It is quite helpful to quickly obtain some initial HTML to the screen in the absence of a network and also ensures that the users don’t have to stare at the white screen for longer than necessary.

Adapt the application shell approach for a website or web app consisting of JavaScript-heavy architectures as it makes use of a service worker to aggressively cache the shell and get the application running. Additionally, it loads the dynamic content for each page using JavaScript.

3. Service Worker

A service worker is essential to add the Push Notifications functionality into your PWA. Therefore, you need to register or set up a service worker for PWA development. It’s a script that your browser runs in the background and enables features that don’t require a web page. Although a service script currently supports features like push notifications and background sync, it might support geofencing and some other features in the nearby future. A service worker uses the web Push API to deliver push notifications. You can head to the “self.registration.pushManager from within your service worker file in order to access it.

4. Add a web app manifest

The web app manifest is a JSON file that informs the browser about your PWA and how it should behave when installed on the user’s mobile device. It encompasses the app name, app icons, splash screen, and the URL where the web app is redirected to when it is launched, similar to what you submit on the app store.

To make your web app installable, include “manifest.json” in the app’s root directory. You can also configure how your PWA should display during launch.

It is because of the web app manifest that the website displays the “Add to home screen” install prompt to the users. When the user visits the website on a browser (Chrome for instance), the web app manifest triggers the browser to automatically prompt the option of installing its PWA provided that the user has visited the site twice with a gap of about five minutes. This is to ensure that it gets displayed to the user only when they have shown a little bit of interest in the website. There’s no point in sending a prompt if the user is visiting the site for the first time.

Performance Measurement

To measure how your PWA is performing and how it has actually enhanced the web experience of your users, you can follow the RAIL system which Google refers to as a user-centric performance model. The model breaks down the user experience into key actions (tap, drag, scroll, load) and helps provide performance goals for each of these actions. RAIL is an acronym for-

Response- refers to how quickly the app responds to the user’s actions (tap or click) before they notice any lag. It needs to provide a response in a reasonable window of time; 0.1 seconds is ideal.

Animation- comprises visual animation, scrolling, and drag. The frame rate of the animation must be 60fps, and in order to achieve 60fps, each frame of the animation must finish in less than 16 milliseconds.

Idle- this is for those functions that don’t need to happen in a quick window time and can be performed when the browser is idle such as searching and sorting data, bootstrapping comments, etc.

Load- Users must not face any trouble while tapping, scrolling, or watching animations, and the respective pages must load within one second.

Final Thoughts

Building a PWA is very economical and time-efficient as compared to native. The primary role here is of the service worker and the web app manifest that makes the web app experience similar to that of a native app.

PWAs are amazing. Numerous popular brands have already been benefitted by building a PWA. Twitter, Starbucks, Ola, and many others have reported significant web growth post the launch of their PWAs. It’s time that you build one as well.