The app event of the Web Manifest API is fired when the browser has successfully installed a page as an application.installed
function handleInstall(ev) {
  console.log('Thank you for installing our app!'); 
} 
window.onappinstalled = handleInstall; The appinstalled event implements the Event interface — it has available the properties and methods defined on this interface.
| Specification | Status | Comment | 
|---|---|---|
| Web App Manifest The definition of 'appinstalled' in that specification. | Working Draft | Initial definition. | 
| Desktop | ||||||
|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | |
| Basic support | Yes | ? | 49 
 | ? | ? | ? | 
| Mobile | |||||||
|---|---|---|---|---|---|---|---|
| Android webview | Chrome for Android | Edge Mobile | Firefox for Android | Opera for Android | iOS Safari | Samsung Internet | |
| Basic support | ? | Yes | ? | 49 
 | ? | ? | ? | 
Window.onappinstalled
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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
    https://developer.mozilla.org/en-US/docs/Web/Events/install