Deep Linking in Mobile Apps: Mastering Custom URL Schemes and Beyond

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Introduction

Deep linking has revolutionized how users interact with mobile apps, seamlessly connecting web content directly to specific functionalities within an app. This in-depth article explores the intricate world of deep linking, focusing on the mechanics of URL Scheme Identification, Universal Links (iOS), App Links (Android), and their implications in mobile app development.

Understanding Deep Linking

Mobile applications often offer a more intuitive and user-friendly interface compared to their web counterparts, leading to an improved user experience. Deep linking plays a pivotal role in this context; it involves URLs to launch a mobile app and guide users directly to particular content on the app. This approach significantly enhances the user experience by facilitating a seamless shift from web-based content to the interactive environment of the app. This seamless integration is made possible through the implementation of two different types of deep linking:

  1. URI scheme (traditional approach) and
  2. Universal Links (Advanced approach).

URI Scheme Deep Linking (traditional approach)

URI Scheme Deep Linking represents a traditional approach in mobile application development, utilizing unique URL schemes, such as “mybank://”, which are registered with the device’s operating system. The primary function of this mechanism is to enable these URLs to directly trigger the launch of an application and navigate the user to a specific page within the app or to execute a particular action. This method proves to be particularly effective in scenarios where the application is already installed on the user’s device. However, one significant limitation of URI Scheme Deep Linking is its inability to redirect users to the app store or prompt them to install the application if it is not already present on their device. This drawback necessitates alternative solutions or supplementary mechanisms to ensure a seamless user experience, especially in situations where app discovery and installation are part of the user journey. Here is a quick summary of the URI scheme:

  • Mechanism: Involves unique URL schemes (e.g., mybank://) registered with the device’s OS.
  • Function: When accessed, these URLs trigger the app to launch and navigate to a specific page or perform an action.
  • Usage: Effective in scenarios where the app is already installed.
  • Drawback: Wont redirect/force user to the app store to install application.

URI Scheme Implementation: It is important to understand how it is implemented across different platforms. For iOS applications, the registration of URL schemes is accomplished by defining them in the app’s Info.plist file. This file acts as a directory for the operating system, informing it of the unique URL schemes that the app can handle. In contrast, Android applications utilize “intent filters” declared in their AndroidManifest.xml file. These filters enable Android apps to handle specific types of intents, including custom URL schemes.

Both the schemes supports parameters passing through URLs. This functionality allows applications to perform specific actions based on the content of the URL, making deep linking more dynamic and useful for app developers and users alike.

However, with the convenience and functionality of URI Scheme Identification comes a significant concern for security. It is imperative for developers to rigorously validate deep links. This validation is crucial in preventing the execution of unwanted actions and in ensuring that the user experience remains secure. Adhering to best practices in the development and implementation of these schemes is essential to safeguard against potential vulnerabilities, thereby maintaining the integrity of the app and the safety of its users.

Summary

  • Registration and Handling:
    • iOS: Apps define URL schemes in the Info.plist file.
    • Android: Apps utilize “intent filters” in the AndroidManifest.xml.
  • Parameter Passing:
    • URLs can include parameters, enabling apps to perform specific actions based on the URL’s content.
  • Security and Best Practices:
    • Validating deep links is essential to prevent unwanted actions.
    • Ensures a secure user experience by adhering to best practices in development and implementation.

The Power and Limitations of Custom URL Schemes

How Custom Schemes Work

  • Unique Identifier: Acts like a web URL, but starts with a custom scheme (e.g., myapp://).
  • App Dependency: Only functional if the app is installed on the device.

Limitations

  • Cannot Override Standard URLs: Custom schemes are specific to the app and cannot hijack standard URLs like “google.com”.
  • User Experience Considerations: Respecting user choices is paramount in app design.

Practical Implementation

  • Example: A custom URL (myapp://profile/john_doe) can direct users to a specific profile within the app.
  • Fallback Strategies: For non-installed apps, consider providing a web-based alternative.

Universal Links (iOS) and App Links (Android) (advanced approach)

Universal Links for iOS and App Links for Android represent an advanced approach in the realm of mobile application development. Unlike traditional methods, these mechanisms leverage standard HTTP/HTTPS links to directly guide users to specific content within an app. A notable advantage of these methods is their fallback behavior: if the app isn’t installed on the user’s device, the link will instead open a web page, ensuring a continuous user experience. Setting up these links requires the hosting of app/site association files on a server, which are essential for validating the domain. However, this advanced approach comes with its own set of challenges. It demands a more sophisticated understanding and implementation at both the application and server levels. This complexity can pose a barrier for developers and organizations that may not have the necessary resources or expertise, highlighting the need for comprehensive knowledge in both app development and server management to effectively utilize Universal Links and App Links. Given below is the quick summary of the Universal Link scheme:

  • Mechanism: These methods allow standard HTTP/HTTPS links to direct users to app content.
  • Fallback: If the app isn’t installed, they open a web page.
  • Setup: Requires app/site association files hosted on a server for domain validation.
  • Drawback: need advance understanding and implementation both on app & server level.

Working principal:

Here’s a closer look at how Universal Links and App Links function on different platforms:

iOS Universal Links

  • Setup Process: This involves the creation of an Apple App Site Association (AASA) file. The file must be properly configured and hosted on the web server to ensure that iOS can access and validate it. Additionally, the app’s Info.plist file needs to be configured to include the necessary URL schemes and domains.
  • Operating System Handling: When a Universal Link is accessed, iOS checks the AASA file to determine whether the link should open in the app or in the Safari browser. If the app is installed and the link is associated with the app according to the AASA file, the link will open directly in the app, bypassing Safari.

Android App Links

  • Setup Process: This requires the use of a Digital Asset Links file, which is similar in function to the AASA file used in iOS. The file must be hosted on the web server and linked to the app. In the app’s AndroidManifest.xml, specific intent filters and configurations must be set up to handle the App Links.
  • Operating System Handling: Android performs a verification process to ensure the app is intended to handle the specific URLs. When a user clicks on an App Link, Android checks the Digital Asset Links file to confirm the app’s association with the website URL. If the verification is successful and the app is installed, the link opens directly in the app, providing a seamless transition from the web to the app.

Conclusion

Deep linking, with its varied methodologies, offers developers a powerful tool to enhance app usability and user engagement. While custom URL schemes provide a tailored approach to app navigation, they come with inherent limitations and responsibilities. Understanding and implementing these techniques correctly is crucial for creating a secure and user-friendly app environment.