Deep Linking

Custom URI schemes were the original form of deep linking for mobile apps. They are like creating a “private internet” for your app, with links that look like myapp://path/to/content. The advantage of custom URI schemes is they are easy to set up and most apps already have one. The disadvantage is a user’s device only knows about this “private internet” if the corresponding app is already installed, and there is no graceful fallback option by default.

Apple introduced Universal Links in iOS 9 as a solution to the lack of graceful fallback functionality in custom URI scheme deep links. Universal Links are standard web links (http://mydomain.com) that point to both a web page and a piece of content inside an app. When a Universal Link is opened, iOS checks to see if any installed device is registered for that domain. If so, the app is launched immediately without ever loading the web page. If not, the web URL (which can be a simple redirect to the App Store) is loaded in Safari.

Google built App Links as the Android equivalent to iOS Universal Links, and they operate in a very similar way: a standard web link that points to both a web page and a piece of content inside an app. This results in a smoother user experience, but since custom URI schemes are still fully supported by every version of Android, App Links have seen very low adoption.