What are deep links?
A deep link is a URL that opens an app directly to a specific screen or piece of content rather than simply launching it to the home screen. Tapping a deep link in an email, a message, or a notification can take someone straight to a product, a profile, or a settings page inside the app. On iOS there are two common ways to build them: a custom URL scheme and Universal Links.
How deep links work on iOS
The older approach is a custom URL scheme. You register a scheme such as myapp:// in the app's Info.plist, and when iOS sees a URL with that scheme it launches your app and hands it the URL to interpret. In SwiftUI you handle the incoming URL with the onOpenURL modifier and route to the right screen. The newer approach, Universal Links, uses ordinary https URLs that point at your website and open the app when it is installed. Both end up calling into your app with a URL that you parse to decide what to show.
Custom URL schemes versus Universal Links
The two approaches differ in trust and fallback. A custom URL scheme is easy to set up, but any app can register the same scheme, and there is no verification that you own it, which makes schemes less suitable for security sensitive links. Universal Links use https and are verified by associating your app with your domain, so only your app can claim those links, and if the app is not installed the same URL opens your website in the browser. For user facing links, Universal Links are usually the better choice, while custom schemes remain handy for internal or app to app navigation.
Common uses and how AppFlight fits
Deep links power marketing campaigns, referral and invite flows, push notification taps that open the relevant screen, and hand-offs between apps. Getting them right means registering the scheme or associated domain and handling the incoming URL in code. AppFlight builds native Swift and SwiftUI projects, so it can configure a custom URL scheme in Info.plist or the Associated Domains setup for Universal Links and wire the handling code, letting an app respond to deep links without configuring it all by hand.
FAQ
What is the difference between a deep link and a Universal Link?
Deep link is the general term for a URL that opens specific content in an app. Universal Links are one kind of deep link on iOS that use https URLs verified against your domain. Custom URL scheme links, like myapp://, are another kind that any app can register and are not verified.
How does an iOS app handle a deep link?
For a custom URL scheme, the scheme is registered in Info.plist and the app handles the incoming URL, for example with onOpenURL in SwiftUI. For Universal Links, the app handles an incoming web URL through the same kind of entry point after the system verifies ownership.
What is deferred deep linking?
Deferred deep linking sends a new user to specific content even when the app is not yet installed. The link routes them to install first, then opens the intended screen on first launch. It usually relies on a third-party SDK, since iOS does not provide it directly.