Nearly everyone will know and understand that to load a web page we enter http:// or more recently (and more importantly) https://, but Apps can also be targeted directly with a custom form of the ‘https’ prefix called a custom scheme. For example mailto: based URL’s will open up the users default mail client when the user clicks a mailto link. For many pre-approved schemes, the browser can also register a web app to handle the custom scheme so that every time the URL is clicked either on a site or in an app on the user’s system it will open the web site.
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