Firebase Docs Reference Interface: MessagingTopicResponse admin.messaging.MessagingTopicResponse interface static Interface representing the server response from the sendToTopic() method. See Send to a topic for code samples and detailed documentation. Property messageId number The message ID for a successfully received request which FCM will attempt to deliver to all subscribed devices. Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 3.0 License, and code samples are licensed under the Apache 2.0 License. For details, see our Site Policies. Java is a registered trademark of Oracle and/or its affiliates. Last updated February 14, 2018.