Ultimate guide to progressive web apps why do companies outsource?

Ultimate guide to progressive web apps why do companies outsource?

Today we have brought to you the ultimate guide to progressive web apps explaining what actually web apps are. And how their technology functions. This blog is for beginners and there is no need for any type of prior knowledge to understand it. We are going to start everything from a new learner perspective and will go from there to fully professional. We will be explaining the fundamentals of progressive web apps that everyone who is going to start learning PWA should know. By the time you would have finished the blog, you would have a definite idea about what progressive web apps are. And how their technology works. Welcome to the Tech Pathway blog, today we are going to share with you the ultimate guide to progressive web apps.why do companies outsource?

Also read:- A Guide to Make Money from Free Apps: Tips and Strategies

What are progressive web apps development?

What are progressive web apps development?

Before knowing about progressive web apps, we are going to understand what web apps are (non-progressive). Web apps are install and run on the host server where everything related to calculation and processing happens. On the other hand, the user’s device works as a screen that allows him/her to see the result. This way the user doesn’t have to install the whole program and process everything on the device rather they can install the web app. It allows them to save space and processing power. Now, when generally developers talk about web apps they also talk about the front end, client-side, and technology that is use.

This concept first comes in form of a web 2.0 dynamic web browser environment. Here the user can be both participative and collaborate. Microsoft has also helped to bring this to life by making interaction seamless by designing the XMLHttpRequest web API in the year 2006. In addition to this, technologies such as Ajax and jQuery developers can show updated information without needing to reload the page again and again. 

Later in the year 2007, Apple introduced the idea of progressive web apps with the help of Progresive web app developers in its new operating system iOS. 

Steve Jobs quotes as “The full Safari engine is inside the iPhone. And so, you can write amazing Web 2.0 and Ajax apps that look exactly and behave exactly like apps on the iPhone. And these apps can integrate perfectly with iPhone services”.

However, later the App Store came into existence and developers left the idea to favor native apps. Yet, Google hasn’t forgotten it and brought it back to life by proposing an advanced version as Service workers. It was thanks to Google and Service Worker that now progressive web apps exist. 

So what exactly are progressive web apps?

The web view is a common technology that is use by every computer as well as mobile devices. It is used to launch PWA.

Well, we can define progressive web apps by 3 conditions

  • PWA loads fast enough for mobile networks
  • PWA loads even when we are offline
  • PWA is installable

The previous version of Web apps can only load when there was an active Internet connection. Later Progressive web apps came and they were installable as well as able to load even without an active Internet connection. 

PWA development is also working as cross-platform apps thanks to them being able to render on the browser and install on every OS. If you want to hire PWA developers then keep reading.

Installation of Progressive web apps

  • Use the HTTPS protocol: The HTTPS protocol is important for your apps since they certified the security of your website. 
  • Register a service worker: Service workers work as a key to everything we will later discuss in the blog. 
  • Implement a web app manifest: The web app manifestation allows the installation of web apps on the user’s devices using JSON files. 

Example of JSON file: <link rel=”manifest” href=”/manifest.json”>

How can you install

  • If the developer is working on a computer machine then he/she will need to navigate to the app domain with Google Chrome to install the progressive web apps. 
  • You can find the installation on the upper bar in Google Chrome. 
  • Once you click on it, you will be able to get the installation prompt. 

In other cases, if you are working on an Android device then after opening Google Chrome you will be shown a banner asking as “Add to Home Screen”. However, shortly companies are planning to rename it as “Install”. 

This happens because there is a function call the “Beforeinstallprompt” event and the “Prompt()” method is call automatically on the Android devices. 

However, the iOS is dependent on the Safari browser so it doesn’t support the “Beforeinstallprompt” event and users will need to follow different steps. Where they can click on the “options” in the upper bar next to the domain address and select “add to home screen” 

Web View

The web view is a common technology that is use by every computer as well as mobile devices. It is used to launch PWA. 

To identify the web view you can open any social media app like Instagram. Now click on any external link. Now, this link will take you to a web page without leaving the app itself. This web page is called web view and these are built-in to most of the software and applications these days. This is also known as an “In-app browser” since you are not launching any stand-alone browser on your device. 

The web view accesses web content using Native web view technology. The same technology is use by Progressive web apps. In other words, you can think of a web view as a browser without the actual browser. Where the only purpose a web view only has to fulfill is to access the web content. 

Most of the time web views have different functionalities so they also require different requirements. This is why we use different WebView APIs for different specifications. 

A browser engine is essentially made out of 2 major components 

  • Render Engine 
  • JavaScript engine

In some cases, when a web view needs advanced access or JS functionalities, it needs to open the browser engine. That makes the process of rendering slower than normal. This is the reason Chrome Team is trying to replace the WebViews with an advanced technology 

known as Trusted Web Activity. 

Features of Web view

  • Chromium for Chrome, with V8 as JS engine.
  • WebKit for Safari, with Nitro as JS engine.
  • Gecko for Firefox, with SpiderMonkey as JS engine.

Chromium offers great support for progressive web apps. Some of the most interesting features it offers are:

  • Offline capabilities
  • Installation through prompt
  • Push Notifications
  • Background Sync
  • Persistent Storage through IndexedDB
  • Web Payment
  • Web Share
  • Access to the camera
  • Access to the audio output
  • Geolocation

On the other hand, Webkit also has some limitations known as

  • There are many offline capabilities with a Cache Storage quota limited to 50MB for Service Workers.
  • There is no “Beforeinstallprompt” event.
  • There is only partial support for manifest.json.
  • There are no Push Notifications.
  • There is no Background Sync.
  • There is no persistent storage and after a few weeks, all your PWA files will be deleted.
  • The access to the camera is restrict to photos only.

However, the WebKit team is working full-time to provide these features as soon as they can. You will need to know about these limitations before you think about selecting technology for your progressive web apps development. For example, there is no need to write the code in the native form if you are developing the app for a mobile platform. Since it involves duplication of the source code (Java Kotlin + Swift). However, other than PWAs developers can also develop natively compiled apps using Flutter, React Native, or Native Script. 

Service Workers

The reason behind the faster loading and processing of progressive web apps is because they follow the App Shell Architecture. It is a minimal HTML, Javascript, and CSS that require to power the user interface. In other words, you can say that an App Shell Architecture is PWA’s substitute for the SDK in a mobile context. 

Steps followed by App Shell Architecture

  • First clean window without any content
  • Then it paints the screen
  • After that, it starts painting any meaningful content on the screen like navigation
  • Then the primary content is print on the screen
  • After that, the rest of the content is print on the screen
  • Your screen is ready to interact

This process of showing web content on the user’s screen is faster and doesn’t require a faster internet connection. 

This architecture heavily relies on the magic aggressively pre-caching this shell by using functionalities of Service workers. Because the developers can enable PWAs to load even when the user’s device doesn’t have an active Internet connection. 

Javascript Thread

To understand how the Service workers help PWAs, we will need to first know that Javascript is a single-threaded language. And single-threaded languages are just the opposite of concurrent. This means developers cannot run two processes at the same time. 

Also, Javascript can only run either on the client-side or server-side. In this case, you will have to decide on the context of different global objects. 

  • window in a browser.
  • global in Node JS.
  • self in workers.

Note: If the developer needs to get the global object they will be require to use the “globalThis” property. 


Javascript workers are programming scripts that execute in the background thread and separate from the main execution thread. 

Also, since the global object is not “Window” they cannot access the DOM. That means if in case, the developer will need any communication between the main thread and javascript worker they will be required to establish a communication. This will be done using the Javascript channel “MessageEvent” interface. 

  • A message can be sent through the Worker.postMessage() method.
  • A message can be received through the Worker.onmessage property.

There are about 3 types of Workers

  • Web workers: These web workers generally have only one functionality as offloading heavy processing from the main thread of the program. For example, it would be a good idea to use web workers for any type of image manipulation tasks. 
  • Worklet: Worklet is also known as the light version of the web workers. It provides access to low-level parts of the pipeline’s access (Javascript -> Style -> Layout -> Paint -> Composite). 
  • Service workers: These are also known as event-driven workers that act as a proxy worker. These service workers are the key technology of PWAs. However, they are not supported by Microsoft’s Internet Explorer. 

Service workers functionality

The Service workers were introduce to replace the deprecated HTML application code. The reason behind that was its ability to handle normal scenarios but couldn’t handle the complex ones. 

Service workers took their functionality one step ahead by working on Old cache. They fundamentally work on files but in some cases, they are capable of handling old cache. In addition to this, developers can also pre-cache these files as well as improve the speed in subsequent loads. Service workers can also be defined as request interceptors. They are also able to proxy any kind of call between server and browser. 

A PWA will only install on the device if it uses a secure HTTP communication protocol. And service workers run on HTTPS which is why they have access to the IndexedDB API. 

The lifecycle of service workers

A life cycle will ensure that the web page is only control by a single service worker. 

There are three steps in a service worker life cycle:

  • Download: the service worker is requested through registration.
  • Install: is attempted when the downloaded service worker file is found to be new.
  • Activate: Activate step will allow the service worker to gain control of clients.

Once a service worker’s life cycle is completed, it goes into an idle state. From there it can be called upon the necessity to handle memory, terminate, as well as call to fetch messages on the server. 

Download the service worker

The service workers are needed to be installed for the very first time when they are being register. This Registration of service workers will be taking place in the main thread so that developers can directly implement the code into the “Index.html”. As well as in a separate file that will be called “main.js”. After that, the developer can say that “sw.js” is their file of service workers. 

Let’ take an example code:

if (‘serviceWorker’ in navigator) {

  window.addEventListener(‘load’, () => {

        navigator.serviceWorker.register(‘/sw.js’).then(registration => {

      // Registration was successful so the service worker was downloaded.

      // OPTION: registration.update();

      console.log(`Service Worker registered! Scope: ${registration.scope}`);

    }, error => {

      // Registration fail so the service worker is not download but just discard. 

      console.error(`Service Worker registration failed: ${error}`);




The registration of a social worker is automatically update every 24 hours. However, it can also be done manually to detect any type of change in the browser. 

Install the service worker

Once the registration is automatically trigger for an update after 24 hours. The developer would have the opportunity of pre-caching requests to some files that will be considered as regular files. These files will consist of the App Shell. 

// —> sw.js

var cacheName = ‘my-site-cache-v1’;

var urlsToCache = [






self.addEventListener(‘install’, event => {


  // OPTION: self.skipWaiting() instead of event.waitUntil()



      .then(cache => {

        // Precaching was successful so a service worker was install.

        console.log(‘Opened cache’);

        return cache.addAll(urlsToCache);

      }, error => {

        // Precaching failed so the service worker is not install. 

        console.error(`Service Worker installation failed: ${error}`);




Activate the service worker

Once the installation is successful the service worker will be ready to control clients. But there are few steps to follow before that. First, we need to activate the event to be execute. 

// —> sw.js

self.addEventListener(‘activate’, event => {


    caches.keys().then((keyList) => {

      return Promise.all(keyList.map((key) => {

        // Same cacheName that we defined before.

        if (key !== cacheName) {

          console.log(‘[ServiceWorker] Removing old cache’, key);

          return caches.delete(key);






Now with this step, the service worker is ready to work and help the progressive web apps to complete their tasks. If you are looking for a Mobile application development company then keep reading.


Progressive app development company

PWAs are great alternatives for web apps. Also, they are perfect choices for multi-platform projects. If you want to invest in Progressive web apps development or hire progressive web app developers for in-house development. Well, then Tech Pathway is a mobile application development company to Hire mobile app developers here for you. Being a Progressive app development company we also offer out-source development services to our clients across the globe. You can contact us today to get an estimate on the development cost of your progressive web app solution and to hire dedicated developers. 

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