How to enable iOS universal links in web-facing Sharepoint on-prem site

Universal links allow to open mobile app when user clicks it inside the site. I.e. if user has appropriate mobile app it will be opened instead of regular browser page which will give better user experience on mobile devices. In this post I will show how to configure universal links for iOS in web-facing Sharepoint on-premise site. At the same time I won’t write about all steps like building mobile app itself, getting its app id, etc – please refer to appropriate resources related with mobile apps development for that.

In order to enable universal links for iOS on your web-facing Sharepoint on-prem site the following steps have to be done:

1. create AASA (Apple app site association) file. File name should be exactly “apple-app-site-association” without extension. It should contain data in json format with predefined structure (see below)
2. put it to the root folder of web-facing site
3. ensure that AASA file is available for anonymous users (robots) with Content-Type = “application/json”

This is how AASA file may look like:

{
  "applinks": {
    "apps": [],
    "details": [ { "appID": "{appId}", "paths": ["*"] } ]
  }
}

(use you app id instead of {appId} placeholder). When file is ready we need to copy it to the IIS folder of our Sharepoint site. Next step is to provide anonymous access and set correct content type. It can be done by modifying web.config of Sharepoint site – we need to add new location element here under configuration tag (usually in web.config of Sharepoint site there are many others location elements – so just put them together):

 <location path="apple-app-site-association">
    <system.web>
      <authorization>
        <allow users="*" />
      </authorization>
    </system.web>
    <system.webServer>
      <staticContent>
        <mimeMap fileExtension="." mimeType="application/json" />
      </staticContent>
    </system.webServer>
  </location>

It will make AASA file available for anonymous users and will set content type to “application/json”.

The last step is to verify that everything is configured properly. It can be done on AASA validator. Result should look like this:

At the end you should have universal links enabled for your web-facing Sharepoint on-prem site.

Update 2020-10-01: guide for enabling Android App links on Sharepoint site is available here: How to enable Android App links in web-facing Sharepoint on-prem site.