The User Messaging Platform (UMP) SDK lets you present an [IDFA message](https://support.google.com/admob/answer/10115027) to your users before requesting their consent for [App Tracking Transparency](https://developer.apple.com/documentation/apptrackingtransparency) (ATT). The IDFA message shows your users how your app uses the identifier. This guide covers using the UMP SDK to present an IDFA message. > [!NOTE] > **Note:** If you enable both GDPR and IDFA messages, refer to [Which message your users will > see](https://support.google.com/admob/answer/10114020#which-message-your-users-will-see) for the possible outcomes. ## Prerequisites Before you begin, make sure you've done the following: - [Set up Google Mobile Ads Flutter Plugin](https://developers.google.com/admob/flutter/privacy.md.txt). - [Create an IDFA message](https://support.google.com/admob/answer/10115331) in the AdMob UI. ## Update Info.plist To show a custom alert message, do the following: 1. Open the `Info.plist` file. 2. Add the `NSUserTrackingUsageDescription` key with a custom message that describes the usage: NSUserTrackingUsageDescription This identifier will be used to deliver personalized ads to you. The usage description appears as part of the IDFA ATT alert when you present the consent form: ![](https://developers.google.com/static/admob/ump/images/idfa-alert.png) Then, link the `AppTrackingTransparency` framework: ![](https://developers.google.com/static/admob/ump/images/link-att-framework.png) Your app then shows an IDFA message before the ATT alert. ## Testing While testing, remember that the ATT alert only appears a single time since [`requestTrackingAuthorization`](https://developer.apple.com/documentation/apptrackingtransparency/attrackingmanager/3547037-requesttrackingauthorization) is a one-time request. The UMP SDK only has a form available to load if the authorization status is [`ATTrackingManagerAuthorizationStatusNotDetermined`](https://developer.apple.com/documentation/apptrackingtransparency/attrackingmanagerauthorizationstatus/attrackingmanagerauthorizationstatusnotdetermined?language=objc). To make the alert appear a second time, you must uninstall and reinstall your app on your test device. ## Request ads with or without IDFA If a user denies ATT, continue to request ads using your ad format's APIs. The Google Mobile Ads Flutter Plugin doesn't send IDFA in the ad request. For more details see, [Select an ad format](https://developers.google.com/admob/flutter/quick-start.md.txt#select_an_ad_format).