How do Progressive Web Apps work?
Posted: Sun Jan 26, 2025 5:04 am
As you've just seen, the Service Worker is the key to a good Progressive Web App. But there are two other players that you need to know about to understand how a Progressive Web App works: the App Shell and the App Manifest . Let's review the role of each of these three elements.
The service worker is a JavaScript file saved as a script in the PWA build. This makes it possible to program any variety of processes and actions that depend on certain events; that is, that react to user activity. In this way, the PWA can load content from a specific link before the user selects it.
The app shell is downloaded to the user's device as part of the website cache. This element is responsible for adapting the appearance of the PWA to the browser the user is using, ensuring that all its functionalities are retained. In addition, this program is responsible for emulating the design of a normal native app. The app shell is what is responsible for dynamically loading the content.
The app manifest is a JSON file that is downloaded from the website's server and allows the user to save the PWA to their home screen as if it were a native mobile app. This file does not contain the entire PWA, but only the most essential elements (usually the app shell ). The app manifest allows you to determine whether the PWA can be loaded without a browser, configure some app functionality, and the ability to send notifications to the user.
Differences between native apps, PWAs and traditional websites
A first difference between native apps, PWAs and traditional websites is in their operation.
Websites must load all or most of their content each time the user loads the page. Native apps, on vp engineering email list the other hand, must be downloaded by the user through an app store such as the Appstore or Play Store, taking up storage space on their device.
PWAs do neither: the user simply adds the web page to their home screen , downloading a lightweight file as part of the page cache. The rest of the “app” is downloaded in the background to the cache without impacting the user experience.
But there is another important difference: their capabilities. Mobile websites are notorious for slow loading times and choppy performance, and this is especially true when it comes to heavier websites. Meanwhile, PWAs can load content immediately.
This means that PWAs can load when the user's network is minimal or non-existent. Native apps can also achieve this, but at the price of taking up storage space on the user's device.
The service worker is a JavaScript file saved as a script in the PWA build. This makes it possible to program any variety of processes and actions that depend on certain events; that is, that react to user activity. In this way, the PWA can load content from a specific link before the user selects it.
The app shell is downloaded to the user's device as part of the website cache. This element is responsible for adapting the appearance of the PWA to the browser the user is using, ensuring that all its functionalities are retained. In addition, this program is responsible for emulating the design of a normal native app. The app shell is what is responsible for dynamically loading the content.
The app manifest is a JSON file that is downloaded from the website's server and allows the user to save the PWA to their home screen as if it were a native mobile app. This file does not contain the entire PWA, but only the most essential elements (usually the app shell ). The app manifest allows you to determine whether the PWA can be loaded without a browser, configure some app functionality, and the ability to send notifications to the user.
Differences between native apps, PWAs and traditional websites
A first difference between native apps, PWAs and traditional websites is in their operation.
Websites must load all or most of their content each time the user loads the page. Native apps, on vp engineering email list the other hand, must be downloaded by the user through an app store such as the Appstore or Play Store, taking up storage space on their device.
PWAs do neither: the user simply adds the web page to their home screen , downloading a lightweight file as part of the page cache. The rest of the “app” is downloaded in the background to the cache without impacting the user experience.
But there is another important difference: their capabilities. Mobile websites are notorious for slow loading times and choppy performance, and this is especially true when it comes to heavier websites. Meanwhile, PWAs can load content immediately.
This means that PWAs can load when the user's network is minimal or non-existent. Native apps can also achieve this, but at the price of taking up storage space on the user's device.