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Deep Linking (Universal Links / App Links)

/dip ˈlɪŋkɪŋ/noun

Filed underMobile DevelopmentMarketingUX

In brief · quick answer

A technique that directs users to specific content inside a mobile app from external links, instead of landing on the app's homepage.

§ 1 Definition

Deep Linking is the practice of using URLs that open specific content within a mobile app rather than just launching the app's main screen. Web URLs (https://yourapp.com/product/123) can open the corresponding screen in the app if the app is installed. Platform implementations differ: Apple uses Universal Links (iOS 9+), Android uses App Links (Android 6+). Both verify domain ownership through a digital asset links file hosted on the website. Deep linking is critical for user acquisition campaigns, email marketing, and cross-app navigation.

§ 2 Types of Deep Links

Three link types matter. Standard Deep Links: Custom URL schemes like `yourapp://product/123`. These work but have a problem: if the app isn't installed, the link fails silently. Universal Links (iOS) and App Links (Android): Regular HTTPS URLs that open the app when installed and fall back to the website when not. These are the recommended approach. Deferred Deep Links: Links that work even after the user installs the app. A user clicks a link, gets redirected to the App Store, installs, opens the app, and lands on the right screen. Services like Branch, AppsFlyer, and Firebase Dynamic Links handle deferred deep linking.

§ 3 Implementation

Implementing deep links requires work on both the web server and the app. For Universal Links (iOS): host an `apple-app-site-association` JSON file at the root of your web domain. For App Links (Android): host an `assetlinks.json` file. On the app side, configure intent filters (Android) or continueUserActivity handling (iOS). Test thoroughly. A broken deep link is worse than no deep link because it frustrates users and wastes ad spend.

§ 4 Use Cases

Deep linking powers essential mobile flows. User Acquisition: Facebook and Google ads link directly to product pages in your app. Email Marketing: Promotional emails open the relevant offer screen. Referral Programs: Invite links open the signup flow. Cross-App Navigation: Open a restaurant in Uber Eats from a Yelp review. Password Reset: Reset a user's password and deep link them to the login screen. Without deep linking, every external link dumps users on your home screen and forces them to navigate manually.

§ 5 In code

// iOS: Handling Universal Links (AppDelegate)
func application(
  _ application: UIApplication,
  continue userActivity: NSUserActivity,
  restorationHandler: @escaping ([UIUserActivityRestoring]) -> Void
) -> Bool {
  guard userActivity.activityType == NSUserActivityTypeBrowsingWeb,
        let incomingURL = userActivity.webpageURL else {
    return false
  }
  // Parse incomingURL and navigate to the right screen
  handleDeepLink(url: incomingURL)
  return true
}

§ 6 Common questions

Q. What happens if the app is not installed when a user clicks a Universal Link?: A. The link falls back to your website. The user lands on the corresponding web page instead of crashing or seeing an error. This is the key advantage over custom URL schemes.
Q. Do I need a third-party service for deep linking?: A. For basic Universal Links and App Links, no. Apple and Google provide all the APIs you need. For deferred deep linking (works through the install process), analytics, and attribution, third-party services like Branch or AppsFlyer are very helpful.

Key takeaways

Deep links send users to specific content inside your app from external URLs.
Universal Links (iOS) and App Links (Android) use HTTPS and fall back to the web.
Deferred deep linking works through the install funnel for acquisition campaigns.
Deep linking is essential for mobile ad attribution, email marketing, and cross-app flows.
Always test deep links thoroughly; broken links waste ad spend and frustrate users.

How Atomic Glue helps

Atomic Glue implements Universal Links and App Links for iOS and Android apps. We set up the server-side association files, configure intent filters, and handle deferred linking for acquisition campaigns. See our Mobile App Development services or get in touch.

Get in touch

# Deep Linking (Universal Links / App Links)

A technique that directs users to specific content inside a mobile app from external links, instead of landing on the app's homepage.

Category: Mobile Development (also: Marketing, UX)

Author: Atomic Glue Editorial Team

## Definition

## Types of Deep Links

Three link types matter. **Standard Deep Links**: Custom URL schemes like `yourapp://product/123`. These work but have a problem: if the app isn't installed, the link fails silently. **Universal Links (iOS)** and **App Links (Android)**: Regular HTTPS URLs that open the app when installed and fall back to the website when not. These are the recommended approach. **Deferred Deep Links**: Links that work even after the user installs the app. A user clicks a link, gets redirected to the App Store, installs, opens the app, and lands on the right screen. Services like Branch, AppsFlyer, and Firebase Dynamic Links handle deferred deep linking.

## Implementation

## Use Cases

Deep linking powers essential mobile flows. **User Acquisition**: Facebook and Google ads link directly to product pages in your app. **Email Marketing**: Promotional emails open the relevant offer screen. **Referral Programs**: Invite links open the signup flow. **Cross-App Navigation**: Open a restaurant in Uber Eats from a Yelp review. **Password Reset**: Reset a user's password and deep link them to the login screen. Without deep linking, every external link dumps users on your home screen and forces them to navigate manually.

## In code

// iOS: Handling Universal Links (AppDelegate)
func application(
  _ application: UIApplication,
  continue userActivity: NSUserActivity,
  restorationHandler: @escaping ([UIUserActivityRestoring]) -> Void
) -> Bool {
  guard userActivity.activityType == NSUserActivityTypeBrowsingWeb,
        let incomingURL = userActivity.webpageURL else {
    return false
  }
  // Parse incomingURL and navigate to the right screen
  handleDeepLink(url: incomingURL)
  return true
}

## Common questions

Q: What happens if the app is not installed when a user clicks a Universal Link?

A: The link falls back to your website. The user lands on the corresponding web page instead of crashing or seeing an error. This is the key advantage over custom URL schemes.

Q: Do I need a third-party service for deep linking?

A: For basic Universal Links and App Links, no. Apple and Google provide all the APIs you need. For deferred deep linking (works through the install process), analytics, and attribution, third-party services like Branch or AppsFlyer are very helpful.

## Key takeaways

Deep links send users to specific content inside your app from external URLs.
Universal Links (iOS) and App Links (Android) use HTTPS and fall back to the web.
Deferred deep linking works through the install funnel for acquisition campaigns.
Deep linking is essential for mobile ad attribution, email marketing, and cross-app flows.
Always test deep links thoroughly; broken links waste ad spend and frustrate users.

## Related entries

Last updated June 2025. Permalink: atomicglue.co/glossary/deep-linking