Implement Robust Mobile Deeplink Handling

This skill implements robust, secure, user-friendly deeplinks for iOS and Android - URL schemes, universal links, app links, and deferred deeplinking. URL structure should be consistent and hierarchical (myapp://category/item/12345), pair with a fallback web URL (https://myapp.com/item/12345) for universal links, stay human-readable and predictable, carry the context needed to restore app state, and plan for versioning and backward compatibility. Platform priority is explicit: iOS should prioritize Universal Links over custom URL schemes for security, Android should implement App Links with proper intent filters and domain verification, and cross-platform stacks (React Native, Flutter) need consistent handling across all of them.

Use it when an app needs verified, secure deeplinking (Universal/App Links) with deferred-link and fallback handling - not a bare custom URL scheme with no validation.

private func handleDeeplink(url: URL) -> Bool {
    let components = URLComponents(url: url, resolvingAgainstBaseURL: true)
    let path = components?.path ?? ""
    switch path {
    case let path where path.hasPrefix("/product/"):
        let productId = String(path.dropFirst("/product/".count))
        navigateToProduct(id: productId)
        return true
    case "/profile":
        navigateToProfile()
        return true
    default:
        return false
    }
}

iOS setup wires NSUserActivity/SceneDelegate continuation handlers to a path-matching switch, backed by an Apple App Site Association JSON declaring which /product/* and /user/profile paths the app claims. Android setup pairs an autoVerify App Links intent filter (https/host) with a separate custom-scheme intent filter, handled in onCreate/onNewIntent by matching intent.data.pathSegments. React Native wraps Linking.getInitialURL() and the url event listener behind a DeeplinkHandler class that regex-parses both the custom scheme and the HTTPS fallback into a screen/params route. Advanced patterns include a DeferredDeeplinkManager that stores a pending deeplink until the user finishes authenticating, and a DeeplinkGenerator that builds shareable links with UTM campaign parameters and a fallbackUrl for users without the app installed. Testing commands are given for both platforms: xcrun simctl openurl and AASA-file curl -I checks for iOS, adb shell am start -a android.intent.action.VIEW -d ... and adb shell pm get-app-links for Android domain-verification status.

Mobile developers implementing deeplinking across iOS, Android, and React Native who need verified Universal/App Link setup plus deferred-link and fallback handling, not a fragile custom-scheme-only implementation. Security and best-practice guidance closes it out: validate every deeplink parameter to prevent injection, use HTTPS for universal/app links, implement proper fallback for unhandled links, test across cold-start/background/foreground app states, monitor deeplink analytics to catch broken links, version the deeplink schema for graceful app updates, and handle malformed URLs, missing parameters, and network failures explicitly rather than letting them crash navigation.