Firebase silent apns notification

Question

Is there a way to send a silent APNS using google's firebase? It seems that if the app is in the background it will always show a notification to the user.

Thanks?

Answer 1

You can send silent APNS messages using the FCM server API https://firebase.google.com/docs/cloud-messaging/http-server-ref

In particular you need to use:

• The data field:

This parameter specifies the custom key-value pairs of the message's payload.

For example, with data:{"score":"3x1"}:

On iOS, if the message is sent via APNS, it represents the custom data fields. If it is sent via FCM connection server, it would be represented as key value dictionary in AppDelegate application:didReceiveRemoteNotification:.

The key should not be a reserved word ("from" or any word starting with "google" or "gcm"). Do not use any of the words defined in this table (such as collapse_key).

Values in string types are recommended. You have to convert values in objects or other non-string data types (e.g., integers or booleans) to string

• The content-available field:

On iOS, use this field to represent content-available in the APNS payload. When a notification or message is sent and this is set to true, an inactive client app is awoken. On Android, data messages wake the app by default. On Chrome, currently not supported.

Full documentation: https://firebase.google.com/docs/cloud-messaging/http-server-ref#downstream-http-messages-json

Answer 2

For a truly silent notification (both foreground and background) using FCM server use these fields:

"to" : "[token]",
"content_available": true,
"priority": "high",
"data" : {
  "key1" : "abc",
  "key2" : 123
}

NOTE: Make sure you are using "content_available" NOT "content-available" with FCM. It's converted for APNS and won't be received properly otherwise. The difference had tripped me up for some time.

Answer 3

I explain this topic more detail on my blog. http://blog.boxstory.com/2017/01/how-to-send-silent-push-notification-in.html

** keypoint is : "content_available:true"

this is sample JSON

{
    "to" : "<device>",
    "priority": "normal",
    "content_available": true, <-- this key is converted to 'content-available:1'
    "notification" : {
      "body" : "noti body",
      "title" : "noti title",
      "link": "noti link "
    }
}

Note: If the above sample JSON is sent, then the notification will be visible to the user. Use below If you don't want the user to see the push notification.

{
  "to": "<device>",
  "priority": "normal",
  "content_available": true <-- this key is converted to 'content-available:1'
}

Answer 4

For guys who do not use the Legacy HTTP as is shown in other answers and use the latest v1 HTTP protocol, I've finally figured out the right way to send silent notifications.

NodeJS example using firebase-admin:

    const message = {
      apns: {
        payload: {
          aps: {
            "content-available": 1,
            alert: ""
          }
        }
      }
    };

    admin
      .messaging()
      .send(message)
      .then(response => {
        // Response is a message ID string.
        console.log("Successfully sent message:", response);
      })
      .catch(error => {
        console.log("Error sending message:", error);
      });

Explanation:

• It seems the payload in apns does not get converted by Firebase in v1 HTTP protocol so you need the original "content-available": 1 for that.
• alert: "" is also necessary. If you ever try to send silent notifications using something like Pusher, you will find only content-available cannot trigger it. Instead, adding additional field such as sound or alert can make it work. See Silent Push Notification in iOS 7 does not work. Since Firebase forbids empty sound, we can use empty alert for this.

Answer 5

The other solutions did not work for me. I wanted a solution that sent data messages to both iOS and Android.

From my testing I have found that the only way to reliably send a data message when my iOS app is in the background is to include an empty notification payload.

Also, as other answers have mentioned, you need to include content_available and priority.

To test this out using a curl command you'll need your FCM server key and the FCM token from the app.

Sample curl command for iOS only. (Reliable data message with no visible notification)

curl -X POST \
  https://fcm.googleapis.com/fcm/send \
  -H 'authorization: key=server_key_here' \
  -H 'content-type: application/json' \
  -d '{
  "to": "fcm_token_here", 
  "priority": "high",
  "content_available": true,
  "notification": {
    "empty": "body"
  },
  "data": {
    "key1": "this_is_a_test",
    "key2": "abc",
    "key3": "123456",
  }
}'

Replace server_key_here and fcm_token_here above with your own.

The below method in your AppDelegate class should be called when the app is in the background and no UI message should be displayed.

func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any],
                 fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
    //get data from userInfo

    completionHandler(UIBackgroundFetchResult.newData)
}

Here's how you would do this using a cloud function and typescript to send to a topic.

const payload = {
    notification: {
        empty: "message"
    },
    data: {
        key1: "some_value",
        key2: "another_value",
        key3: "one_more"
    }
}

const options = {
    priority: "high",
    contentAvailable: true //wakes up iOS
}

return admin.messaging().sendToTopic("my_topic", payload, options)
    .then(response => {
        console.log(`Log some stuff`)
    })
    .catch(error => {
        console.log(error);
    });

---

The above seems to consistently work for iOS and sometimes work for Android. I've come to the conclusion that my backend will need to determine platform before sending out a push notification to be most effective.