What are FCM tokens?

An FCM Token, or much commonly known as a registrationToken like in google-cloud-messaging. As described in the GCM FCM docs: An ID issued by the GCM connection servers to the client app that allows it to receive messages . Note that registration tokens must be kept secret.

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Do FCM tokens change?

Similarly to how GCM works, the FCM token can change due to token-rotation . Note: the token rotation is a rare-event. Don’t expect to see it often. But still, if you care about the token you should implement onTokenRefresh() to be informed of changes.

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What is FCM device token?

Firebase Cloud Messaging (FCM) is a messaging solution that lets you reliably send messages at no cost to both Android & iOS devices . Using FCM, you can send data payloads (via a message) to a device for a specific application. Each message can transfer a payload of up to 4KB to a client.

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