Priority - shaikhalvee/FCM GitHub Wiki

• Normal priority - (data messages) won't open network connections on a sleeping device, and their delivery may be delayed to conserve the battery (e.g. notifications of new email or other data to sync)

• High priority - (notification messages) allowing the FCM service to wake a sleeping device when possible and open a network connection to your app server (set high priority if the message is time-critical and requires the user's immediate interaction)

Valid values are "normal" and "high"

{
  "to" : "bk3RNwTe3H0:CI2k_HHwgIpoDKCIZvvDMExUdFQ3P1...",
  "priority" : "normal",
  "notification" : {
    "body" : "This week's edition is now available.",
    "title" : "NewsMagazine.com",
    "icon" : "new"
  },
  "data" : {
    "volume" : "3.21.15",
    "contents" : "http://www.news-magazine.com/world-week/21659772"
  }
}