Firebase Cloud Messaging XMPP protocol

This document provides a reference for the XMPP syntax used to pass messages between your app server, client apps, and Firebase Cloud Messaging (FCM). Your app server must connect to these endpoints:

// Production
fcm-xmpp.googleapis.com:5235

// Testing
fcm-xmpp.googleapis.com:5236

The available parameters and options fall into these categories:

Downstream message syntax
Downstream message error response codes
Upstream message syntax
FCM control messages

Downstream message syntax

This section gives the syntax for sending downstream messages.

Downstream XMPP messages (JSON)

The following table lists the targets, options, and payload for XMPP JSON messages.

Table 1 Targets, options, and payload for downstream XMPP messages (JSON).

Parameter	Usage	Description
Target
`to`	Optional, string	This parameter specifies the recipient of a message. The value can be a device's registration token, a device group's notification key, or a single topic (prefixed with `/topics/`). To send to multiple topics, use the `condition` parameter.
`condition`	Optional, string	This parameter specifies a logical expression of conditions that determines the message target. Supported condition: Topic, formatted as "'yourTopic' in topics". This value is case-insensitive. Supported operators: `&&`, `\|\|`. Maximum two operators per topic message supported.
Options
`message_id`	Required, string	This parameter uniquely identifies a message in an XMPP connection.
`collapse_key`	Optional, string	This parameter identifies a group of messages (e.g., with `collapse_key: "Updates Available"`) that can be collapsed so that only the last message gets sent when delivery is resumed. This is intended to avoid sending too many of the same messages when the device comes back online or comes out of doze. There is no guarantee of the order in which messages get sent. Note: A maximum of 4 different collapse keys is allowed at any given time. This means FCM can simultaneously store 4 different messages per client app. If you exceed this number, there is no guarantee which 4 collapse keys FCM will keep.
`priority`	Optional, string	Sets the priority of the message. Valid values are "normal" and "high." On iOS, these correspond to APNs priorities 5 and 10. By default, notification messages are sent with high priority, and data messages are sent with normal priority. Normal priority optimizes the client app's battery consumption and should be used unless immediate delivery is required. For messages with normal priority, the app may receive the message with unspecified delay. When a message is sent with high priority, it is sent immediately, and the app can display a notification.
`content_available`	Optional, boolean	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, and the message is sent through APNs as a silent notification and not through the FCM connection server. Note that silent notifications in APNs are not guaranteed to be delivered, and can depend on factors such as the user turning on Low Power Mode, force quitting the app, etc. On Android, data messages wake the app by default. On Chrome, currently not supported.
`mutable_content`	Optional, JSON boolean	Currently for iOS 10+ devices only. On iOS, use this field to represent `mutable-content` in the APNS payload. When a notification is sent and this is set to `true`, the content of the notification can be modified before it is displayed, using a Notification Service app extension. This parameter will be ignored for Android and web.
`time_to_live`	Optional, number	This parameter specifies how long (in seconds) the message should be kept in FCM storage if the device is offline. The maximum time to live supported is 4 weeks, and the default value is 4 weeks. For more information, see Setting the lifespan of a message.
`delivery_receipt_ requested`	Optional, boolean	This parameter lets the app server request confirmation of message delivery. When this parameter is set to `true`, FCM sends a delivery receipt when the device confirms that it received the message. Note: this parameter is not supported for messages sent to iOS devices. The default value is `false`.
`dry_run`	Optional, boolean	This parameter, when set to `true`, allows developers to test a request without actually sending a message. The default value is `false`.
Payload
`data`	Optional, object	This parameter specifies the key-value pairs of the message's payload. For example, with `data:{"score":"3x1"}:` On iOS, if the message is delivered by APNs, it represents the custom data fields. If it is delivered by FCM, it is represented as a key value dictionary in `AppDelegate application:didReceiveRemoteNotification:`. On Android, this results in an intent extra named `score` with the string value `3x1`. The key should not be a reserved word ("from", "message_type", or any word starting with "google" or "gcm"). Do not use any of the words defined in this table (such as `collapse_key`).