# Creating a Message Filter App Extension Create an app extension that helps identify unwanted messages. ## Discussion To create a Message Filter app extension, add a target that uses the Message Filter Extension template to the Xcode project for your containing app. The principal view controller in your app extension is a subclass of [`ILMessageFilterExtension`](/documentation/IdentityLookup/ILMessageFilterExtension) that adopts the [`ILMessageFilterQueryHandling`](/documentation/IdentityLookup/ILMessageFilterQueryHandling) protocol. If you have servers that can help your app extension determine how to handle a message, you must add the Associated Domains capability to your Xcode project and specify those domains. Then, you must set up shared credentials as described in , substituting `messagefilter` for `webcredentials` throughout the steps. Lastly, you must specify the domains in your `Info.plist` file, which should look similar to the dictionary shown below. ```xml NSExtension NSExtensionPrincipalClass MessageFilterExtension NSExtensionAttributes ILMessageFilterExtensionNetworkURL https://www.example-sms-filter-application.com/api NSExtensionPointIdentifier com.apple.identitylookup.message-filter ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)