Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
The prompt() method of the BeforeInstallPromptEvent interface allows a developer to show the install prompt at a time of their own choosing. Typically this will be called in the event handler for the app's custom install UI.
This method must be called in the event handler for a user action (such as a button click) and may only be called once on a given BeforeInstallPromptEvent instance.