What is deep linking in a mobile app?

It is a link that opens a specific screen inside your app instead of just launching it, such as a product page or an order status.

What is the difference between Universal Links and custom URL schemes?

Universal Links and Android App Links are verified web addresses that open the app or the website. Custom schemes are unverified and fail if the app is missing.

What is a deferred deep link?

A link that survives installation, so a new user who installs from a link still lands on the intended content on first launch.

Why do links open the browser instead of the app?

Common causes are incorrect verification files, redirects on those files, or in-app browsers in social apps that bypass app opening.

Is it safe to put data in deep link URLs?

Avoid sensitive data. Use short lived tokens, validate every parameter, and check authorisation on the server.

Deep Linking in Mobile Apps: Universal Links and Deferred Links

A customer taps a link in a WhatsApp message promoting your spring sale. If your app is installed, they expect to land directly on that product page. If it is not, they expect to install it and still end up on that product page. Too often, they land on the home screen, a login wall, or a plain web page that asks them to download an app and then forgets why they came. Each of those failures loses a customer who was already interested.

Deep linking is the set of techniques that connect a link to the exact place inside your app. This guide explains the types of links, how they work on iOS and Android, how to handle users who have not installed your app yet, and a clear implementation process for startup teams.

What Deep Linking Means

A deep link is a link that opens a specific screen inside a mobile app rather than just launching it. A link to a restaurant menu, an order status, a course lesson, or a referral invite are all examples. Deep links power marketing campaigns, notifications, referrals, email, and sharing between users.

The three main types

Custom URL schemes. Links such as myapp://product/42. They are simple to set up, but any app can claim the same scheme, they trigger an error if the app is not installed, and modern platforms are less friendly to them.
Universal Links (iOS) and App Links (Android). Ordinary web addresses that open your app when it is installed and your website when it is not. The operating system verifies that your domain and app belong together, which makes them secure and reliable.
Deferred deep links. Links that survive the install. A user without the app taps a link, goes to the store, installs, and on first launch the app still knows where to send them.

For most products, Universal Links and App Links are the foundation, with deferred deep linking added for acquisition flows.

Why Deep Links Deserve Real Attention

Higher conversion from campaigns. Sending visitors straight to the relevant screen removes steps where people drop off.
Better re-engagement. Push notifications and emails that open the right screen feel useful, while those that open the home screen feel like noise.
Working referrals. A friend's invite that carries a code through the install makes referral programs actually function.
Cleaner attribution. Links that carry campaign information let you see which channels bring valuable users.
Consistent web and app experience. One URL works everywhere, which simplifies sharing and search visibility.

A Real-World Example

Imagine a hypothetical food delivery startup running a festival campaign with a discount on a specific restaurant. Ads, WhatsApp broadcasts, and email all use the same link.

With a basic setup, users who already have the app get thrown to the home screen and must search for the restaurant themselves. New users reach the app store, install, open the app, and find no trace of the offer. Many of them leave. With a proper setup, the existing users land on the restaurant page with the discount applied. New users install, and on first launch the app reads the stored context, takes them through a short sign-up, and then shows the same restaurant and offer. The campaign spend is identical, but the path from tap to order is shorter in both cases. That is the kind of difference teams often see when journeys are connected end to end, though the size of the improvement depends on the audience and the offer.

How Universal Links and App Links Work

On iOS

You host a small association file on your domain that lists which paths your app can handle. You also add an associated domains entitlement to the app. When a user taps a matching link, iOS checks the file, confirms the match, and opens the app, passing the full URL to your code.

On Android

You declare intent filters in the app manifest for your domain and paths, and host a digital asset links file that ties your domain to your app signing certificate. Android verifies that file and can then open your app directly without a chooser dialog.

Common to both

Your site must serve the verification file over HTTPS, without redirects, with the correct content type.
The link must be tapped, not typed or pasted into a browser address bar, to trigger app opening in most cases.
Some in-app browsers and social apps open links inside their own viewer, which can bypass app opening. You need a visible fallback, such as an "Open in app" button on the web page.

Step-by-Step Implementation Process

Design your link structure. Map screens to clean URL paths such as /product/42 or /order/9001. Use the same structure on your website so one link works on every platform.
Set up domain verification. Publish the iOS association file and the Android asset links file, and check them with the validators provided by the platform vendors.
Configure the apps. Add associated domains on iOS and intent filters on Android for the exact paths you support.
Build a central link router. Parse every incoming link in one place and translate it to a screen and parameters. Avoid scattering parsing logic across the codebase.
Handle cold and warm starts. A link can arrive when the app is closed, in the background, or already open on another screen. Test all three.
Handle authentication. If the target screen requires login, store the destination, complete login, and then continue to it. Never drop the user on the home screen after sign-in.
Add deferred deep linking. Use a dedicated link service or the store referrer mechanisms where available to carry context across installation, and apply it on first launch.
Add web fallbacks. If the app is not installed, show a useful web page for the same content with a store button, rather than a blank "download our app" wall.
Validate everything. Treat link parameters as untrusted input. Check IDs, permissions, and formats before acting on them.
Test on real devices. Verify behaviour across operating system versions, major browsers, email clients, and messaging apps before launch.

Connecting Links to Measurement and Onboarding

A deep link is only as valuable as what you learn from it. Add campaign parameters to links and record the source, medium, and destination in your analytics when the app opens. If you are setting up that tracking, our guide to mobile app analytics and funnel instrumentation explains how to define events that connect clicks to activation.

The first launch after a deferred link is also a critical moment. New users arriving with context should still get a short, focused introduction rather than a long tutorial. Our article on mobile app onboarding design for a fast first win offers patterns that fit well with link-driven installs.

Security and Privacy Considerations

Avoid sensitive data in URLs. Links can be logged, shared, and forwarded. Use short-lived tokens, not passwords or personal details.
Validate before acting. A malicious link could point to another user's order or an admin screen. Always check authorisation on the server.
Prefer verified links over custom schemes. Because another app can register the same scheme, custom schemes should not carry anything confidential.
Respect tracking rules. Attribution and device matching are subject to platform policies and privacy regulations. Use consented, platform-approved methods and describe them in your privacy policy.
Expire one-time links. Password reset and invitation links should work once and expire quickly.

Key Benefits of Doing Deep Links Well

Shorter journeys. Fewer taps between interest and action means more completed purchases and sign-ups.
Useful notifications. Messages that open the right place earn trust and reduce opt-outs.
Reliable referrals and invites. Context persists through install, so a friend's invitation still works.
Clearer marketing insight. You learn which campaigns lead to meaningful actions, not only installs.
A single linking strategy. One URL structure serves web, iOS, Android, email, and social posts.

Common Problems and Fixes

If a link works in your test but not for your customers, check where they tapped it.

Link opens the browser instead of the app. Re-check the verification files, redirects, and whether the app was installed from a build that carries the correct entitlements.
Link works from Notes but not from a social app. The in-app browser is likely intercepting it. Provide an explicit open-in-app button.
User lands on the home screen after login. Store the pending destination before authentication and resume it afterwards.
Deferred link lost after install. Confirm the matching method, handle the delay between install and first open, and fall back gracefully with a generic welcome.
Different behaviour across Android makers. Test on a few popular devices, since some manufacturers adjust default link handling.

When to Get Help

Basic Universal Links and App Links are a reasonable task for most mobile teams. Complex needs, such as multi-domain setups, cross-platform frameworks, referral systems, or attribution across several ad networks, benefit from experience. Our mobile app development services cover link architecture, onboarding, and analytics as part of a single build, so these pieces work together from the start.

Conclusion

Deep linking is easy to ignore until a campaign underperforms and you discover that interested people never reached the right screen. Treat links as part of your product design. Choose a clean URL structure, adopt verified Universal Links and App Links, add deferred deep linking for new installs, and route everything through one well-tested handler.

Start by auditing the five most important journeys in your marketing, such as ads, notifications, referrals, email, and sharing, and check what actually happens when each link is tapped by an existing user and by a new one. Fixing those paths will usually repay the effort quickly.

Frequently Asked Questions

What is deep linking in a mobile app?: It is a link that opens a specific screen inside your app instead of just launching it, such as a product page or an order status.
What is the difference between Universal Links and custom URL schemes?: Universal Links and Android App Links are verified web addresses that open the app or the website. Custom schemes are unverified and fail if the app is missing.
What is a deferred deep link?: A link that survives installation, so a new user who installs from a link still lands on the intended content on first launch.
Why do links open the browser instead of the app?: Common causes are incorrect verification files, redirects on those files, or in-app browsers in social apps that bypass app opening.
Is it safe to put data in deep link URLs?: Avoid sensitive data. Use short lived tokens, validate every parameter, and check authorisation on the server.