Deep linking is the foundation of modern mobile app navigation, but the terminology can be confusing. Deep links, Universal Links, App Links, and deferred deep links all serve different purposes and work through different mechanisms. This guide breaks down each type so you can choose the right approach for your app.
What Is a Deep Link?
A deep link is any URL or URI that sends a user to a specific screen inside a mobile app rather than the app's home screen or a generic webpage. The term is broad and covers several distinct technologies.
The oldest form of deep linking uses custom URI schemes (sometimes called URL schemes). These follow a format like myapp://product/123. When a user taps a link with that scheme, the operating system checks whether an app is registered to handle it and opens that app directly.
Custom URI schemes are simple to implement. You register a scheme in your app's configuration and add a handler. No server setup is required. However, they have significant limitations. Any app can register the same scheme, creating a collision risk. If the app is not installed, the link fails entirely with no fallback. And because they are not standard HTTP URLs, they cannot be indexed by search engines.
What Are Universal Links and Android App Links?
Universal Links (iOS) and Android App Links are the platform-native replacements for custom URI schemes. Both use standard HTTPS URLs and require domain verification, which solves the security and reliability problems of custom schemes.
Universal Links work by hosting a file called apple-app-site-association (AASA) at https://yourdomain.com/.well-known/apple-app-site-association. This JSON file declares which URL paths should open in your app. When a user taps a matching HTTPS link, iOS checks the verified association and opens the app directly. If the app is not installed, the link opens in Safari as a normal webpage.
Android App Links follow the same pattern. You host a assetlinks.json file at https://yourdomain.com/.well-known/assetlinks.json that declares your app's package name and signing certificate fingerprint. When android:autoVerify="true" is set in your app's intent filters, Android verifies the association at install time and routes matching URLs directly to your app without showing a disambiguation dialog.
Both technologies offer three key advantages over custom URI schemes. First, domain verification ensures only the verified domain owner can claim the link, eliminating hijacking. Second, HTTPS fallback means users without the app still reach your content on the web. Third, standard URLs are indexable by search engines.
What Are Deferred Deep Links?
Deferred deep links solve the problem that neither Universal Links nor App Links address on their own: what happens when the user does not have the app installed yet.
With a standard Universal Link or App Link, if the app is not installed, the user lands on the web page. That is useful, but it does not preserve the intended destination. If a user clicks a link to a specific product, gets redirected to the App Store, installs the app, and opens it, they land on the home screen instead of the product page.
Deferred deep links fix this. They store the intended destination during the redirect to the app store. After the user installs and opens the app for the first time, the deferred deep link resolves and routes them to the correct screen. The link's context survives the install process.
This is particularly valuable for affiliate marketing and user acquisition campaigns. When an affiliate shares a link to a specific feature or product inside your app, deferred deep linking ensures the referred user arrives at exactly the right place, even if they need to install the app first.
How Do These Types Compare?
| Feature | Custom URI Scheme | Universal Links / App Links | Deferred Deep Links |
|---|---|---|---|
| URL format | myapp://path |
https://domain.com/path |
https://domain.com/path |
| Server setup required | No | Yes (AASA / assetlinks.json) | Yes |
| Works if app not installed | No (fails) | Falls back to web | Redirects to store, then routes after install |
| Domain verification | No | Yes | Yes |
| Search engine indexable | No | Yes | Yes |
| Handles install gap | No | No | Yes |
Which Should You Use?
For most production apps in 2026, the answer is Universal Links and App Links as your baseline, with deferred deep linking layered on top for acquisition flows.
Custom URI schemes still have a place for app-to-app communication where both apps are under your control, but they should not be your primary deep linking mechanism for user-facing links. The lack of verification and fallback makes them unsuitable for marketing, sharing, or any scenario where the user might not have your app installed.
If you are running an affiliate program or any referral-based growth strategy, deferred deep links are essential. Without them, you lose attribution and context every time a referred user needs to install your app before reaching the content.
How Insert Affiliate Handles Deep Linking
Insert Affiliate's Insert Links feature generates deferred deep links for your affiliates automatically. Each Insert Link detects whether the user is on iOS or Android and whether the app is already installed. If the app is installed, the link opens the correct screen directly. If not, it routes through the App Store or Google Play and preserves the affiliate attribution through the install process.
Insert Links are built on Universal Links (iOS) and Android App Links, using verified HTTPS URLs with proper AASA and assetlinks.json configuration. Insert Affiliate also integrates with third-party deep linking platforms including Branch.io and AppsFlyer if you already have one in place.
For developers evaluating deep linking strategies, the choice of technology directly impacts conversion rates and attribution accuracy. Getting this layer right is foundational to everything built on top of it, from analytics to affiliate tracking to user onboarding.