The Apple App Site Association file, often shortened to AASA, is a small JSON document that securely connects an iOS app with its website. It acts as a digital handshake between the two, confirming that the app and the domain truly belong to the same owner.
This connection allows features such as Universal Links, shared web credentials, and handoff experiences between the app and its website to work safely and reliably. With AASA, users can move smoothly between mobile web and app content without confusion, redirects, or duplicate logins.
When a user clicks a link on an iPhone or iPad, iOS needs to know whether to open the page in Safari or inside the corresponding app. Universal Links make this possible. However, to prevent malicious apps from impersonating legitimate websites, Apple requires proof that the app and the domain are truly connected.
That proof comes from the AASA file.
This file lives on your web domain, usually at
https://example.com/apple-app-site-association
It lists the apps that are associated with that domain and defines which parts of the website each app is allowed to handle.
For example, the file might tell iOS that all links beginning with example.com/news/ should open directly in the app, while other parts of the site continue to open in Safari.
When a user installs or updates an app, iOS automatically downloads the AASA file from the corresponding website. The device then verifies the connection between the app and the domain before enabling Universal Links or shared credentials.
If the app is installed and a user taps a supported link, it will open directly inside the app. If the app is not installed, the link will open in Safari instead. This seamless experience helps users stay engaged without interruptions or extra steps.
Here is a simplified example of what an AASA file looks like:
{
"applinks": {
"apps": [],
"details": [
{
"appID": "9JA89QQLNQ.com.apple.wwdc",
"paths": ["/wwdc/news/", "/videos/wwdc/2025/*"]
},
{
"appID": "ABCD.com.apple.wwdc",
"paths": ["*"]
}
]
}
}
In this example, iOS knows that both apps belong to the same domain but handle different URL paths. If both are installed, the system prioritizes the app listed first in the AASA file.
Because iOS only updates the AASA file when an app is installed or updated, any changes made to the hosted file will not take effect on users’ devices until they reinstall or update the app. This makes it important to plan updates carefully and test them thoroughly before release.
For developers and marketers, AASA plays a crucial role in creating a smooth and secure user journey.
The AASA file is essential for enabling Universal Links, which are Apple’s version of deep links for iOS. Universal Links let iPhone and iPad users open app content directly from standard web URLs.
Platforms like Grovs simplify this entire process. Grovs handles the technical configuration needed for deep linking and ensures that your app and domain remain correctly associated. This allows teams to enable Universal Links and deferred deep links across iOS with minimal setup time and no risk of configuration errors.
With Grovs, even marketers and product managers without engineering expertise can implement AASA functionality in just a few minutes.
The Apple App Site Association file is the foundation that allows apps and websites to communicate securely on iOS. It ensures that Universal Links, password autofill, and other integrated features function properly and safely.
For marketers, it means smoother user journeys and higher engagement. For developers, it provides verified domain ownership and safe deep linking. For users, it means fewer interruptions and more reliable app experiences.
Grovs streamlines this setup, helping teams configure Apple App Site Association and Universal Links with ease while maintaining security and consistency across every platform.