What is a Deep Link?

A deep link is a URL or URI that opens a specific screen, object, or action inside a mobile app — a product, a level, a cart, a checkout — rather than the app home screen or the store listing. On the web the same idea is an ordinary path such as /product/42. In apps the store, the web, and the binary are different environments, so routing needs its own mechanism.

In user acquisition and affiliate marketing a deep link closes the gap between what the creative promised and the first screen after the click. Without it, traffic from Meta, Google Ads, or Apple Search Ads usually lands on the store listing or a web landing. After install the user sees a cold start and loses the ad context. That drops install→event CR and later LTV.

Types

Custom URL scheme. A URI such as myapp://product/42. It works only if the app is already installed and registered the scheme with the OS. Weak points: scheme collisions and hijacking — another app can claim the same scheme.
Universal Links (iOS) and App Links (Android). A normal HTTPS URL on the developer’s domain. If the app is installed and the association file is valid (apple-app-site-association / assetlinks.json), the OS opens the app; otherwise the web. This is the default standard after iOS 9 and Android 6.
Deferred deep link. The app is not installed yet: the click goes to the store, and after install an MMP or SDK restores the original path and campaign parameters. Without deferred linking you cannot honestly send a new user to what the creative promised.
Contextual / one-link. One URL covers web, iOS, and Android: the platform chooses app, store, or site and carries click ID, sub id, and UTM through the install.

What a deep link is not

The term is mixed up with two neighbouring glossary entries — they are different objects.

Redirect tracking is a click-logging scheme: HTTP 302 through the tracker domain, IP/UA capture, click ID minting, then a redirect to a landing or offer. The redirect may contain a deep link as the final URL; the redirect itself does not open an in-app screen.

Direct linking in arbitrage is buying without your own pre-landing: ad → tracker → advertiser offer URL. That is web-funnel length, not in-app routing. “Straight to the offer” is not an app deep link.

UA chain

A typical CPI flow: ad → tracking URL (network macros + UTM) → MMP or tracker → store or Universal Link. After install the SDK sends the install and in-app events; a postback or S2S call closes attribution. On iOS the path hits ATT and SKAdNetwork: deferred parameters and creative IDs are often stripped, leaving a coarse conversion value.

If the app is already installed, a Universal Link opens the target screen and skips the store. The goal is then an in-app event (purchase, registration), not an install. That is the default retargeting case: return the user to an abandoned cart, not to home.

Tracking and reconciliation

A parameter-less deep link is useless to a buyer: you cannot tell which creative or campaign produced the event. The URL carries click ID, sub1–subN, sometimes utm_source / utm_campaign. MMPs (AppsFlyer OneLink, Adjust, Branch and peers) store the click until install and stitch it to first open. A buyer’s tracker usually logs the click on the redirect; restoring the in-app path is the advertiser’s SDK job.

Reconcile three ledgers: cabinet clicks, MMP installs, tracker events. Gaps usually mean a broken association file, query params stripped on the way to the store, or install fraud — click spam glued onto organic installs.

Where it is used

In the mobile apps vertical a deep link is the baseline UA and retargeting tool. In commerce apps it carries the SKU and promo from the creative. In games it opens a mode or “continue after tutorial.” On CTV the path often goes through a QR code: the TV is not tappable, the phone opens the store or the app. Install-offer cards sometimes say “deep link required”: the advertiser accepts traffic only if the post-install path is controlled.

Breakage and limits

The common failure is that the link opens web or store instead of the screen: expired association cert, team ID / package name mismatch, a redirect chain iOS does not treat as a Universal Link. Custom schemes break when the user installs a second app with the same scheme. Android App Links need verified Digital Asset Links; without verification the OS shows a chooser.

Store and ad-platform policies ban bait-and-switch: the creative must match the destination screen. A broken deep link produces high post-install bounce and disapproval risk.