Add Check For Cached Site Association File For iOS as a devops TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1242 TILs and counting..._
+_1243 TILs and counting..._
 
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@@ -157,6 +157,7 @@ _1242 TILs and counting..._
 - [Aliasing An Ansible Host](devops/aliasing-an-ansible-host.md)
 - [Allow Cross-Origin Requests To Include Cookies](devops/allow-cross-origin-requests-to-include-cookies.md)
 - [Allow HTTPS Through Your UFW Firewall](devops/allow-https-through-your-ufw-firewall.md)
+- [Check For Cached Site Assocation File For iOS](devops/check-for-cached-site-association-file-for-ios.md)
 - [Check The Status of All Services](devops/check-the-status-of-all-services.md)
 - [Check The Syntax Of nginx Files](devops/check-the-syntax-of-nginx-files.md)
 - [Connect To An RDS PostgreSQL Database](devops/connect-to-an-rds-postgresql-database.md)

devops/check-for-cached-site-association-file-for-ios.md

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+# Check For Cached Site Assocation File For iOS
+
+Apple caches your [AASA (Apple App Site
+Association)](https://developer.apple.com/documentation/Xcode/supporting-associated-domains)
+file periodically. This is used for signaling what site URLs should be Univeral
+Links to your iOS app.
+
+You can view the contents of the cached site association file by inserting your
+domain into the end of this URL --
+`https://app-site-association.cdn-apple.com/a/v1/[domain]`.
+
+For instance, if my app's domain is `www.my-app.com`, then I'd pull up
+`https://app-site-association.cdn-apple.com/a/v1/www.my-app.com` to see what is
+cached.
+
+Additionally, you can run your site association file through a validator by
+entering your domain into the form at [AASA
+Validator](https://branch.io/resources/aasa-validator/).
+
+[source](https://david.y4ng.fr/implementing-and-testing-universal-links/)