A deep link is a link that takes a person to a particular piece of content inside a mobile app, such as a product page, a playlist or a booking screen, instead of dropping them on the app's home screen or its app store listing. The term began on the web, meaning a hyperlink to an inner page rather than a front page. On mobile it exists because apps were not originally addressable: without a deep link, a click on a shoe advertisement opens the retailer's mobile site or the app's first screen, and the shopper has to search again.

Google's Ads Help Center defines deep links as links that send mobile users straight to relevant pages in an app rather than to a website. What happens after the tap depends on the operating system, whether the app is installed and which app the tap came from.

There are three main technical families, plus one technique layered on top.

Custom URI schemes were the first. An app registers a prefix such as example:// with the operating system, and any link beginning with that prefix opens the app, with the rest of the string (example://product/123) telling it which screen to show. Schemes are simple but unprotected: nothing stops another app from claiming the same prefix, and if the app is not installed the link usually produces an error.

Universal Links are Apple's answer, introduced with iOS 9 in 2015. A Universal Link is an ordinary HTTPS address on a domain the app owner controls. The app declares the domain in an Associated Domains entitlement (applinks:example.com), and the website hosts a JSON file called apple-app-site-association at /.well-known/apple-app-site-association, served over HTTPS without redirects. The file lists the app identifiers (team ID plus bundle ID) and the URL paths the app handles, for instance /products/*. When a matching link is tapped, iOS opens the app and passes it the URL; if the app is absent, the same link opens in Safari. Apple's developer documentation describes Universal Links as "a potential attack vector" and tells developers to validate every parameter.

Android App Links work the same way on Google's platform. The app's manifest declares an intent filter with the VIEW action, the BROWSABLE and DEFAULT categories, http or https schemes and android:autoVerify="true". According to Android's developer documentation, on Android 6.0 (API level 23) and higher, installing the app triggers a check of https://hostname/.well-known/assetlinks.json, a Digital Asset Links file that lists the app's package name and signing certificate fingerprint. Verified links open the app without the old "open with" dialog.

Deferred deep linking solves the install problem. According to AppsFlyer's glossary, when a person without the app clicks, a link service records the intended destination against the click, sends the person to the App Store or Google Play and, after the first launch, the provider's software development kit (SDK) in the app retrieves the stored destination and opens it. Standard deep links mostly serve re-engagement; deferred ones serve acquisition.

In practice, a campaign link from a mobile measurement partner (MMP) such as Branch, AppsFlyer (OneLink) or Adjust strings these together: a redirect on the provider's domain records the click, detects the platform, tries the Universal Link or App Link, and falls back to a scheme or store. Vendors call links carrying extra data, such as a referral code, contextual deep links.

Origin and evolution

Deep linking was a legal fight before it was an engineering one. In 1996 The Shetland Times sued The Shetland News in Scotland over links to its stories, and in 1997 Ticketmaster sued Microsoft for linking past its homepage from the Sidewalk city guides. Both cases settled. In Ticketmaster v. Tickets.com, around 2000, a US court held that deep linking was lawful provided ownership of the linked pages was clear.

Mobile deep linking grew out of custom URL schemes in early iPhone and Android apps. Google began indexing app content for search in October 2013, deep linking from results into Android apps. Facebook announced App Links at its F8 conference on April 30, 2014, an open standard of web page meta tags mapping URLs to apps. "It's a shame that the URL is not a big deal on mobile right now," Ilya Sukhar, chief executive of Facebook-owned Parse, told TechCrunch. Branch Metrics was founded on April 15, 2014, betting that links needed their own infrastructure.

The platform owners then took over the mechanism. Apple shipped Universal Links in iOS 9 in September 2015. Google announced Android M, with verified links, at Google I/O on May 28, 2015, and released it as Android 6.0 on September 29, 2015. Android 12, released in 2021, tightened the rules: according to Google's Ads Help Center, unverified links now open in the browser without a disambiguation dialog.

Google's own link service followed the opposite arc. Firebase Dynamic Links, which handled deferred deep linking for free, was flagged as "no longer recommended for new projects" in May 2023, according to The Pragmatic Engineer. A Google spokesperson told the newsletter that native App Links and Universal Links had made cross-platform journeys "seamless" and that ecosystem changes had "impacted our ability to provide a consistently stable experience". The service ceased operation on August 25, 2025, the same date as the goo.gl shortener. According to the Firebase FAQ, clicked links now return an HTTP 404 error, and Google pointed developers needing deferred deep linking towards Adjust, Branch or AppsFlyer.

Why it matters for marketers

For app advertisers, the deep link is the difference between a click and a conversion. Google launched Web to App Connect in May 2022 to find missing deep links in Search, Display and Shopping campaigns, claiming conversion rates twice as high for advertisers with a correct integration. In September 2025 it extended the tool to YouTube, Demand Gen and Hotel ads. A 30-page handbook from Adjust and Google Ads published on September 17, 2025 cited internal data showing a 2.8 times higher conversion rate for clicks landing in an app rather than on a mobile site. Those figures come from the companies selling the tools, without published methodology.

Analytics products now audit links directly. Google Analytics 4 added a downloadable report of deep links to implement or fix in August 2024, and in October 2024 flagged misconfigured App Links and Universal Links ranked by engagement. Adjust launched TrueLink, a single cross-platform link, on September 24, 2024.

Deep links also carry re-engagement measurement on iOS. Apple's AdAttributionKit, introduced at WWDC 2024, measures re-engagement on iOS 18 and later, using Universal Links to land existing users on specific screens. That matters because since App Tracking Transparency took effect on April 26, 2021, the mobile advertising ID is unavailable for most iOS users and SKAdNetwork never shipped re-engagement support. MNTN's connected TV integration with AppsFlyer requires a OneLink template.

Limitations and disputes

The most common complaint is breakage. A Universal Link only fires when the operating system receives the tap. Social apps such as Instagram, TikTok and LinkedIn open links in embedded browsers, and according to an Airbridge analysis published in September 2026, those browsers "do not pass the tap to the operating system", so the link loads as a web page and campaign context never reaches the app. That is a vendor's characterisation. Association files also fail silently: a redirect or a wrong certificate fingerprint can disable verification.

Platform policy fragments behaviour. Google's App Connect documentation says third-party redirect links such as Branch or OneLink are not supported, while MMPs depend on redirects to record clicks, so advertisers maintain different link formats per channel.

Privacy is the third issue. Deferred deep linking requires matching a pre-install click with a post-install open, historically done with device IDs or probabilistic signals such as IP address. Apple's Link Tracking Protection, introduced with Safari 17 in 2023, strips query parameters identified as cross-site tracking, though according to WebKit, parameters used only for campaign attribution pass through. URLs themselves can leak sensitive context: an IMDEA Networks study found six of nine AI chatbot web clients sent conversation URLs or titles to trackers.

Dependence on intermediaries carries risk too: Firebase Dynamic Links users had roughly two years to migrate. Kochava now lists deep linking implementation among the requirements it certifies.

Not the same as

A hyperlink or backlink points to a web page; a deep link, in its mobile sense, points into an app.

A redirect is a server instruction that forwards a request to another address. MMP links use redirects to log clicks before handing off, but the redirect is the plumbing, not the destination. A reverse proxy, by contrast, relays requests without changing the visible address.

Universal Link versus App Link is a platform distinction: both are verified HTTPS deep links, Apple's checked through apple-app-site-association, Google's through assetlinks.json.

URL parameter tracking means appending tags such as utm_source to a link. Parameters can ride on a deep link, but they do not open apps.

A store redirect from an end card or playable ad sends a person to an App Store listing, not to content inside the app.

Recent developments

The newest pressure comes from television and AI. Google added QR codes to non-skippable YouTube ads on connected TV in May 2024, sending viewers to a campaign landing page on a phone. By May 2026, YouTube described QR codes as the older workaround and moved checkout onto the television itself through Buy with Google Pay. Google's Universal Commerce Protocol, announced on January 11, 2026, similarly renders checkout inside the AI experience. Whether assistants deep link into merchant apps or keep the transaction for themselves remains an open commercial question.

Timeline

  • 1996 - The Shetland Times sues The Shetland News over deep links; the case settles.
  • 1997 - Ticketmaster sues Microsoft over Sidewalk deep links; settled with a licensing deal.
  • c. 2000 - US court in Ticketmaster v. Tickets.com finds deep linking lawful where ownership is clear.
  • October 2013 - Google begins indexing Android app content for search results.
  • April 15, 2014 - Branch Metrics founded.
  • April 30, 2014 - Facebook announces App Links at F8.
  • May 28, 2015 - Google announces Android M with verified links at Google I/O.
  • September 2015 - Apple ships Universal Links with iOS 9.
  • September 29, 2015 - Android 6.0 released with App Links verification.
  • April 26, 2021 - App Tracking Transparency takes effect with iOS 14.5.
  • 2021 - Android 12 opens unverified web links in the browser by default.
  • May 2022 - Google Ads announces Web to App Connect.
  • May 2023 - Firebase Dynamic Links marked as no longer recommended for new projects.
  • 2023 - Apple introduces Link Tracking Protection with Safari 17.
  • June 2024 - Apple announces AdAttributionKit with re-engagement for iOS 18.
  • August 27, 2024 - Google Analytics adds deep link recommendations.
  • September 24, 2024 - Adjust launches TrueLink.
  • August 25, 2025 - Firebase Dynamic Links shuts down.
  • September 5, 2025 - Web to App Connect expands to YouTube, Demand Gen and Hotel ads.
  • September 17, 2025 - Adjust and Google Ads publish the web-to-app handbook.
  • January 11, 2026 - Google announces the Universal Commerce Protocol.
  • May 13, 2026 - YouTube announces Buy with Google Pay checkout on TV.

Summary

Who: App developers and advertisers implement deep links; Apple and Google control the verification mechanisms; mobile measurement partners such as Branch, AppsFlyer and Adjust operate link infrastructure; ad platforms including Google Ads use deep links in app and web campaigns.

What: A deep link is a URL that opens a specific screen in an app or a specific inner web page. The main forms are custom URI schemes, iOS Universal Links, Android App Links and deferred deep links that survive an app install.

When: Web deep linking disputes date to 1996. Verified mobile deep links arrived with iOS 9 and Android 6.0 in 2015. Firebase Dynamic Links shut down on August 25, 2025.

Where: Deep links run on iOS and Android devices, in advertising clicks, email, social posts, QR codes and connected TV campaigns, with association files hosted on the advertiser's own domain.

Why: Landing people on the right in-app screen rather than a homepage or store page removes friction. Google reports conversion rates two to 2.8 times higher for app landings, though the figures are self-reported.