Universal Links have been available since iOS 9, but their behavior has changed with nearly every major iOS release. AASA file format changes, new validation rules, CDN caching behavior, and Safari interaction quirks all vary by version. If you support a range of iOS versions, you need to know what works where.<\/p>\n\n\n\n
This article documents the significant Universal Links changes across iOS versions so you can test and configure accordingly.<\/p>\n\n\n\n
For Universal Links fundamentals, see universal links: everything you need to know<\/a>. For iOS 17 specifically, see Universal Links changes in iOS 17<\/a>.<\/p>\n\n\n\n iOS 9 (2015) introduced Universal Links. The initial implementation established the core concepts that remain today:<\/p>\n\n\n\n The original AASA format used The iOS 10 and 11 did not introduce major changes to Universal Links behavior. The core functionality remained the same. Notable points:<\/p>\n\n\n\n iOS 13 was the biggest change since the introduction of Universal Links. Apple introduced the modern AASA format with the The legacy format is still supported on iOS 13+. If you need to support iOS 9-12, you can include both formats in the same AASA file. iOS will use the format it understands:<\/p>\n\n\n\n For details on the modern format, see AASA wildcards and path matching<\/a>.<\/p>\n\n\n\n iOS 14 introduced two significant changes:<\/p>\n\n\n\n Starting with iOS 14, Apple's CDN fetches and caches AASA files from your domain. Devices no longer download the AASA file directly from your server. Instead:<\/p>\n\n\n\n This improved reliability (your server being down does not break Universal Links for already-installed apps) but introduced caching delays. Changes to your AASA file may take hours to days to propagate through Apple's CDN.<\/p>\n\n\n\n You can check Apple's cached version:<\/p>\n\n\n\n For CDN caching details, see CDN and AASA caching<\/a>.<\/p>\n\n\n\n iOS 14 also introduced App Clips, which share the AASA infrastructure. The AASA file gained an iOS 15 added support for managed Associated Domains via MDM (Mobile Device Management). This is relevant for enterprise apps:<\/p>\n\n\n\n Apple's documentation: Supporting Associated Domains<\/a>.<\/p>\n\n\n\n iOS 16 introduced:<\/p>\n\n\n\n In developer mode, iOS fetches the AASA file directly from your server instead of Apple's CDN, making development and testing faster.<\/p>\n\n\n\n For testing approaches, see testing Universal Links<\/a>.<\/p>\n\n\n\n iOS 17 brought the most significant tightening of Universal Links validation since iOS 14. Key changes:<\/p>\n\n\n\n For detailed iOS 17 changes, see Universal Links changes in iOS 17<\/a>.<\/p>\n\n\n\n iOS 18 continued the trend of incremental improvements:<\/p>\n\n\n\n For SwiftUI-specific handling, see Universal Links with SwiftUI<\/a>.<\/p>\n\n\n\niOS 9: The Beginning<\/h2>\n\n\n\n
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\/.well-known\/apple-app-site-association<\/code> or \/apple-app-site-association<\/code>.<\/li>\nappID<\/code> (singular) and a paths<\/code> array:<\/p>\n\n\n\n{\n "applinks": {\n "apps": [],\n "details": [\n {\n "appID": "TEAMID.com.example.app",\n "paths": ["\/product\/*", "\/category\/*"]\n }\n ]\n }\n}\n<\/code><\/pre>\n\n\n\napps<\/code> key was required to be an empty array. Apple's documentation at the time: Support Universal Links<\/a>.<\/p>\n\n\n\nKey Behaviors in iOS 9<\/h3>\n\n\n\n
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Content-Type: application\/json<\/code>.<\/li>\niOS 10-11: Stability<\/h2>\n\n\n\n
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iOS 13: The Modern AASA Format<\/h2>\n\n\n\n
components<\/code> array:<\/p>\n\n\n\n{\n "applinks": {\n "details": [\n {\n "appIDs": ["TEAMID.com.example.app"],\n "components": [\n { "\/": "\/product\/*", "comment": "Product pages" },\n { "\/": "\/admin\/*", "exclude": true, "comment": "Exclude admin" }\n ]\n }\n ]\n }\n}\n<\/code><\/pre>\n\n\n\nWhat Changed<\/h3>\n\n\n\n
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appIDs<\/code> (plural)<\/strong> replaced appID<\/code> (singular). You can now list multiple app IDs in a single entry.<\/li>\ncomponents<\/code> array<\/strong> replaced paths<\/code>. Each component is an object with a \/<\/code> key for the path pattern.<\/li>\n"exclude": true<\/code> instead of the NOT<\/code> prefix.<\/li>\n?<\/code> key in components.<\/li>\n#<\/code> key in components.<\/li>\ncomment<\/code> field<\/strong> for documentation within the AASA file.<\/li>\nUIWindowSceneDelegate<\/code> receive Universal Links via scene(_:continue:)<\/code> instead of the app delegate method. Both still work.<\/li>\n<\/ul>\n\n\n\nBackward Compatibility<\/h3>\n\n\n\n
{\n "applinks": {\n "apps": [],\n "details": [\n {\n "appID": "TEAMID.com.example.app",\n "paths": ["\/product\/*"]\n },\n {\n "appIDs": ["TEAMID.com.example.app"],\n "components": [\n { "\/": "\/product\/*" }\n ]\n }\n ]\n }\n}\n<\/code><\/pre>\n\n\n\niOS 14: Apple CDN and App Clips<\/h2>\n\n\n\n
Apple CDN for AASA Files<\/h3>\n\n\n\n
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app-site-association.cdn-apple.com<\/code>) periodically fetches it.<\/li>\nhttps:\/\/app-site-association.cdn-apple.com\/a\/v1\/yourdomain.com\n<\/code><\/pre>\n\n\n\nApp Clips<\/h3>\n\n\n\n
appclips<\/code> section alongside applinks<\/code>. See Universal Links vs App Clips<\/a> for a comparison.<\/p>\n\n\n\niOS 15: Managed Associated Domains<\/h2>\n\n\n\n
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managed<\/code> key in the AASA file's components<\/code> controls which paths are available to managed apps.<\/li>\n<\/ul>\n\n\n\niOS 16: Developer Mode and Alternate Modes<\/h2>\n\n\n\n
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?mode=developer<\/code> flag for the Associated Domains entitlement allows bypassing Apple's CDN validation during development:<\/li>\n<\/ul>\n\n\n\napplinks:yourdomain.com?mode=developer\n<\/code><\/pre>\n\n\n\niOS 17: Stricter Validation<\/h2>\n\n\n\n
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Content-Type: application\/json<\/code>. Some servers that previously served it with application\/octet-stream<\/code> saw breakage.<\/li>\niOS 18: Continued Refinement<\/h2>\n\n\n\n
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onOpenURL<\/code> modifier in SwiftUI received better integration with the scene lifecycle.<\/li>\n<\/ul>\n\n\n\nVersion Compatibility Matrix<\/h2>\n\n\n\n