When developing iPhone apps, one common challenge is linking them to web functionalities seamlessly. One question developers often ask is: "Is it possible to register an http domain-based URL scheme for iOS apps, similar to how YouTube or Maps do it?" This article delves into the intricacies of URL schemes, web-to-app linking, and how developers can achieve this integration.

Understanding URL Schemes

URL schemes are an essential part of how apps interact with each other and the web. They allow external calls to open an app directly and can pass specific information, such as parameters or paths.

Custom URL Schemes vs. Universal Links

On iOS, there are two primary methods to handle URL interactions:

1. Custom URL Schemes:
   • These are custom protocols created by developers for their apps.
   • They are not constrained to only http or https but can be named anything, like myapp:// .
   • Useful for deep-linking directly into specific parts of the app.
2. Universal Links:
   • Introduced to replace the limitations of custom URL schemes and provide seamless web-to-app transitions.
   • They use standard http or https protocols.
   • Require the app and website to be from the same domain.

Registering URL Schemes

Registering URL schemes on iOS involves declaring them in the app's Info.plist . This XML configuration file is integral for ios applications, containing crucial data about how the app interacts with the system.

Example of a Custom URL Scheme:

• This file is hosted on the website's server and defines the paths that your app can handle.
• It needs to be placed at https://yourdomain.com/apple-app-site-association .
• Configure the app to know about the domains it has been associated with, by setting Associated Domains under Capabilities in Xcode.
• Use applinks:yourdomain.com under the Associated Domains keys.
• Implement the appropriate methods in the app delegate to handle URLs when opened from Universal Links.
• The main method is application(_:continue:restorationHandler:) .
• Control Over Domain: Only domains you own or control can be used with Universal Links due to the necessity of uploading the AASA file.
• Fallback Mechanisms: If Universal Links fail (e.g., AASA misconfiguration), users are directed to the browser version.
• Security: The AASA file allows for secure handling of URL links to specific paths with https, reducing the risk of spoofing compared to custom URL schemes.