> [!NOTE] > **Note:** Key-value segmentation is available only for AdMob Pro users. For details, reach out to your Google account manager. Key-value segmentation lets you define custom targeting to segment users through an ad request. For details on key-value segmentation, such as adding a key-value pair in the AdMob UI, see [Add key-value segmentation to a mediation group](https://support.google.com/admob/answer/14916631). This page guides you through implementing key-value segmentation when configuring an ad request using Google Mobile Ads SDK for React Native. ## Before you begin To set up key-value segmentation in your app, you must first [add key-value segmentation to a mediation group](https://support.google.com/admob/answer/14916631). ## Attach key-value pairs to an ad request After setting up your custom key-value pairs in the AdMob UI, attach the pairs to an ad request in your application. Set the [`customTargeting`](https://developers.google.com/admob/react-native/reference/interface/AdRequest.md.txt#AdRequest.customTargeting) property on the [`AdRequest`](https://developers.google.com/admob/react-native/reference/interface/AdRequest.md.txt) object to a key-value record representing your custom targeting data. The following example segments users by duration in an app: ```typescript const daysInApp = 1; const request: AdRequest = { adUnitId: AD_UNIT_ID, customTargeting: { USER_DURATION: daysInApp < 3 ? 'NEW' : 'MATURE', }, }; ``` ## Test the key-value segmentation setup To test your implementation on custom key-value pairs, send an ad request and check the [response info](https://developers.google.com/admob/react-native/response-info.md.txt#response_info_details) object. Verify that the value of the `mediation_group_name` field matches your expected mediation group name. The following example verifies a mediation group name in the ad response: ```json { "responseId": "r6_DZtitA8Gi2OMPyKeksAI", ... "responseExtras": { "mediation_group_name": "Mediation group for new users" } } ```