[Home](./index.md) > [@firebase/messaging](./messaging.md) > [MessagePayload](./messaging.messagepayload.md) > [collapseKey](./messaging.messagepayload.collapsekey.md) ## MessagePayload.collapseKey property The collapse key of the message. See [Non-collapsible and collapsible messages](https://firebase.google.com/docs/cloud-messaging/concept-options#collapsible_and_non-collapsible_messages) Signature: ```typescript collapseKey: string; ```