When you support universal links, iOS 9 users can tap a link to your website and get seamlessly redirected to your installed app without going through Safari. If your app isn’t installed, tapping a link to your website opens your website in Safari.
Generally, any supported link clicked in Safari, or in instances of UIWebView/WKWebView should open the app.
For iOS 9.2 and less, this will only work on a device. iOS 9.3 also supports the simulator.
iOS remembers the user’s choice when opening Universal Links. If they tap the top-right breadcrumb to open the link in Safari, all further clicks will take them to Safari, and not the app. They can switch back to opening the app by default by choosing Open in the app banner on the website.