Firebase FCM silent push notifications for iOS

Remove "notification" key value pair and add "content_available": true

It will look like this

{ 
    "to" : "...",
    "priority": "high",
    "content_available": true,
    "data" : {
      ....
    }
}

This should make it a silent APNS and you need to handle with corresponding APNS delegate methods.

You will need to handle this through delegates Refer this firebase documentation for details: https://firebase.google.com/docs/cloud-messaging/concept-options

I found an workaround. I put an empty value for "sound" in "notification" field and the silent notifications are delivered even when the application is in background.

{ 
    "to" : "...",
    "priority": "high",
    "notification": {
        "sound": ""
    },
    "data" : {
      ....
    }
}

My hunch is that Apple does not allow silent notifications with a 'high' priority and somehow "notification": {"sound": ""} tricks the APNS that this notification is not a silent one.