Why links are not opening in apps?

How do I get links to open in app instead of browser?

I have a Rails app that has some images that link to other pages in the app.

These images have an :external parameter to make the link open in the same app window. These links work fine in desktop browsers, but in mobile devices (including iPhones) they open in the browser rather than being redirected to the external URL.
Does anyone know how I can make this image link behave like it normally would in mobile browsers? In other words, how do I configure it so mobile devices will not open the link in their browser, but instead in the app? In a tag in your , add data-external-start-url as the href of the tag.