How does Progressive Web App work?

Progressive Web Apps (PWAs) use modern web capabilities to deliver fast, engaging, and reliable mobile web experiences that are great for users and businesses. Progressive Web Apps combine many of the advantages of native apps and the Web. PWAs evolve from pages in browser tabs to immersive apps by taking ordinary HTML and JavaScript and enhancing it to provide a first-class native-like experience for the user.

PWAs deliver a speedy experience even when the user is offline or on an unreliable network. There is also the potential to incorporate features previously available only to native applications, such as push notifications.

There are components, which allow the website works as a PWA

# Web App Manifest (JSON)

The web app manifest is a JSON file that tells the browser about your Progressive Web App and how it should behave when installed on the user's desktop or mobile device. A typical manifest file includes the app name, the icons the app should use, and the URL that should be opened when the app is launched.

Manifest files are?supported?in Chrome, Edge, Firefox, UC Browser, Opera, and the Samsung browser. Safari has partial support.

# Service Workers

A service worker is another technical element that supports one of the main features of progressive web applications — the offline work mode, background syncs, and push notifications typical for native apps. The service worker is a JavaScript file running separately from the web page/app. It responds to user interactions with the app, including network requests made from pages it serves. Because the service worker runs only to process a specific event, its lifetime is short.

Offline work mode.?The service worker allows for caching an?application shell?(interface), so it loads instantly on repeat visits. The necessary dynamic content (i.e. message or payment history, shopping cart, avatars) is refreshed every time the connection is back. These mechanics allow for decent app performance and improved user experience. For example, a messenger user won’t see the difference between the online and offline modes regarding interface: It still works; a message history is available. However, messaging requires a connection.

Push notifications.?Push notifications are an efficient tool for user re-engagement through the content and prompt updates from websites they like. Progressive web apps can send push notifications even when the browser is closed, and the app isn’t active.

Background synchronization.?The service worker is also in charge of this feature. It delays actions until stable connectivity is back. For example, the message sent right before the connection fails will be marked as sent and then will be delivered as soon as service is restored. So, servers can send periodic updates to the app allowing it to update itself when the connection is restored.

# Application shell architecture

?PWAs tend to be architected around an application shell. This contains the local resources that your web app needs to load the skeleton of your user interface so it works offline and populates its content using JavaScript. If the application shell has been cached by service worker, then on repeat visits the app shell allows you to get meaningful pixels on the screen really fast without the network. Making use of an app shell is not a hard requirement for building PWAs, but it can result in significant performance gains when cached and served correctly.

The shell of the functionality is loaded and displayed to the user (and potentially cached by the service worker so that it can be accessed offline), and then the page content is loaded dynamically as the user navigates around the app. This reliably and instantly loads on your users' screens, similar to what is seen in native applications.

The app shell should:

• Load fast
• Use as little data as possible
• Use static assets from a local cache
• Separate content from navigation
• Retrieve and display page-specific content (HTML, JSON, etc.)
• Optionally, cache dynamic content

# Secure Protocol / HTTPS / Transport Layer Security

For service workers to work we need to add a TLS certificate to the site. Simply speaking service work will function only if the site is HTTPS.

All websites should be protected with HTTPS, even ones that don't handle sensitive data. HTTPS prevents intruders from tampering with or passively listening in on the communications between your site and your users.

A page can't qualify as a Progressive Web App (PWA) if it doesn't run on HTTPS; many-core PWA technologies, such as service workers, require HTTPS.

In order to be a PWA, the web application must have an SSL certificate installed on its web server. The SSL certificate provides a secure, encoded connection between the frontend app and the backend server. SSL certificate ensures that data is transmitted securely between the web app and the eCommerce and CMS systems.?

With certificate authority like LetsEncrypt, it is simple to enable HTTPS (SSL/TLS) for your eCommerce websites. Being a secure store is not only a good strategy but also vital for eCommerce sites to keep customer information safe.