Progressive Web Apps (PWAs) are web applications that use modern web capabilities to deliver an app-like experience to users. They are reliable, fast, and engaging. Ionic provides a robust framework to build PWAs with ease, leveraging its powerful tools and components.

1. Progressive Enhancement: PWAs work for every user, regardless of browser choice, because they are built with progressive enhancement as a core tenet.
2. Responsive Design: PWAs fit any form factor, from desktop to mobile devices.
3. Connectivity Independence: PWAs can work offline or on low-quality networks.
4. App-like Interactions: PWAs feel like an app to the user with app-style interactions and navigation.
5. Fresh: Always up-to-date thanks to the service worker update process.
6. Safe: Served via HTTPS to prevent snooping and ensure content hasn't been tampered with.
7. Discoverable: Identifiable as "applications" thanks to W3C manifests and service worker registration, allowing search engines to find them.
8. Re-engageable: Features like push notifications make re-engagement easy.
9. Installable: Users can add apps they find most useful to their home screen without the hassle of an app store.
10. Linkable: Easily shareable via URL and do not require complex installation.

First, create a new Ionic project if you don't have one already:

Ionic provides a PWA toolkit that can be added to your project:

This command will:

• Add a service worker to your project.
• Create a manifest.json file.
• Update your index.html to include the manifest and service worker.

The manifest.json file contains metadata about your app. Update it to reflect your app's details:

Service workers are scripts that your browser runs in the background, separate from a web page, opening the door to features that don't need a web page or user interaction. They are essential for PWAs.

Angular's PWA package already includes a basic service worker setup. You can find the configuration in ngsw-config.json.

Build your project for production:

Serve your app locally to test it:

Open your browser and navigate to http://localhost:8080. You should see your app running as a PWA.

Deploy your PWA to a web server. Ensure your server supports HTTPS, as PWAs require a secure context.

1. Objective: Convert an existing Ionic app to a PWA.
2. Steps:
   • Add PWA support using the Angular PWA package.
   • Configure the manifest.json file.
   • Ensure the service worker is correctly set up.
   • Build and test the app locally.
   • Deploy the app to a web server.

1. Add PWA Support:

   ng add @angular/pwa --project app
   

2. Configure manifest.json: Update the manifest.json file with your app's details.

3. Build and Test:

   ionic build --prod
   npx http-server ./www
   

4. Deploy: Deploy the contents of the www directory to your web server.

In this section, you learned about Progressive Web Apps (PWAs) and how to set up a PWA using Ionic. You covered the key concepts of PWAs, added PWA support to an Ionic project, configured the manifest file, implemented service workers, and built and tested your PWA. Finally, you deployed your PWA to a web server. This knowledge will help you create engaging, reliable, and installable web applications using Ionic.