# Publishing Amazon SNS notifications with platform-specific payloads
You can use the Amazon Web Services Management Console or Amazon SNS APIs to send custom messages with platform-specific payloads to mobile devices. For information about using the Amazon SNS APIs, see [Mobile push API actions](mobile-push-api.md) and the `SNSMobilePush.java` file in `[snsmobilepush.zip](samples/snsmobilepush.zip)`.
## Sending JSON-formatted messages
When you send platform-specific payloads, the data must be formatted as JSON key-value pair strings, with the quotation marks escaped.
The following examples show a custom message for the FCM platform.
```
{
"GCM": "{\"fcmV1Message\": {\"message\": {\"notification\": {\"title\": \"Hello\", \"body\": \"This is a test.\"}, \"data\": {\"dataKey\": \"example\"}}}}"
}
```
## Sending platform-specific messages
In addition to sending custom data as key-value pairs, you can send platform-specific key-value pairs.
The following example shows the inclusion of the FCM parameters `time_to_live` and `collapse_key` after the custom data key-value pairs in the FCM `data` parameter.
```
{
"GCM": "{\"fcmV1Message\": {\"message\": {\"notification\": {\"title\": \"TitleTest\", \"body\": \"Sample message for Android or iOS endpoints.\"}, \"data\":{\"time_to_live\": 3600,\"collapse_key\":\"deals\"}}}}"
}
```
For a list of the key-value pairs supported by each of the push notification services supported in Amazon SNS, see the following:
**Important**
Amazon SNS now supports Firebase Cloud Messaging (FCM) HTTP v1 API for sending mobile push notifications to Android devices.
March 26, 2024 – Amazon SNS supports FCM HTTP v1 API for Apple devices and Webpush destinations. We recommend that you migrate your existing mobile push applications to the latest FCM HTTP v1 API on or before June 1, 2024 to avoid application disruption.
+ [Payload Key Reference](https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/PayloadKeyReference.html#/apple_ref/doc/uid/TP40008194-CH17-SW1) in the APNs documentation
+ [Firebase Cloud Messaging HTTP Protocol](https://firebase.google.com/docs/reference/fcm/rest/v1/projects.messages) in the FCM documentation
+ [Send a Message](https://developer.amazon.com/sdk/adm/sending-message.html) in the ADM documentation
## Sending messages to an application on multiple platforms
To send a message to an application installed on devices for multiple platforms, such as FCM and APNs, you must first subscribe the mobile endpoints to a topic in Amazon SNS and then publish the message to the topic.
The following example shows a message to send to subscribed mobile endpoints on APNs, FCM, and ADM:
```
{
"default": "This is the default message which must be present when publishing a message to a topic. The default message will only be used if a message is not present for
one of the notification platforms.",
"APNS": "{\"aps\":{\"alert\": \"Check out these awesome deals!\",\"url\":\"www.amazon.com\"} }",
"GCM": "{\"data\":{\"message\":\"Check out these awesome deals!\",\"url\":\"www.amazon.com\"}}",
"ADM": "{\"data\":{\"message\":\"Check out these awesome deals!\",\"url\":\"www.amazon.com\"}}"
}
```
## Sending messages to APNs as alert or background notifications
Amazon SNS can send messages to APNs as `alert` or `background` notifications (for more information, see [Pushing Background Updates to Your App](https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/pushing_background_updates_to_your_app) in the APNs documentation).
+ An `alert` APNs notification informs the user by displaying an alert message, playing a sound, or adding a badge to your application’s icon.
+ A `background` APNs notification wakes up or instructs your application to act upon the content of the notification, without informing the user.
### Specifying custom APNs header values
We recommend specifying custom values for the `AWS.SNS.MOBILE.APNS.PUSH_TYPE` [reserved message attribute](sns-message-attributes.md#sns-attrib-mobile-reserved) using the Amazon SNS `Publish` API action, Amazon SDKs, or the Amazon CLI. The following CLI example sets `content-available` to `1` and `apns-push-type` to `background` for the specified topic.
```
aws sns publish \
--endpoint-url https://sns.us-east-1.amazonaws.com \
--target-arn arn:aws:sns:us-east-1:123456789012:endpoint/APNS_PLATFORM/MYAPP/1234a567-bc89-012d-3e45-6fg7h890123i \
--message '{"APNS_PLATFORM":"{\"aps\":{\"content-available\":1}}"}' \
--message-attributes '{ \
"AWS.SNS.MOBILE.APNS.TOPIC":{"DataType":"String","StringValue":"com.amazon.mobile.messaging.myapp"}, \
"AWS.SNS.MOBILE.APNS.PUSH_TYPE":{"DataType":"String","StringValue":"background"}, \
"AWS.SNS.MOBILE.APNS.PRIORITY":{"DataType":"String","StringValue":"5"}}' \
--message-structure json
```
**Note**
Ensure that the JSON structure is valid. Add a comma after each key-value pair, except the last one.
### Inferring the APNs push type header from the payload
If you don't set the `apns-push-type` APNs header, Amazon SNS sets header to `alert` or `background` depending on the `content-available` key in the `aps` dictionary of your JSON-formatted APNs payload configuration.
**Note**
Amazon SNS is able to infer only `alert` or `background` headers, although the `apns-push-type` header can be set to other values.
+ `apns-push-type` is set to `alert`
+ If the `aps` dictionary contains `content-available` set to `1` and *one or more keys* that trigger user interactions.
+ If the `aps` dictionary contains `content-available` set to `0` *or* if the `content-available` key is absent.
+ If the value of the `content-available` key isn’t an integer or a Boolean.
+ `apns-push-type` is set to `background`
+ If the `aps` dictionary *only* contains `content-available` set to `1` and *no other keys* that trigger user interactions.
**Important**
If Amazon SNS sends a raw configuration object for APNs as a background-only notification, you must include `content-available` set to `1` in the `aps` dictionary. Although you can include custom keys, the `aps` dictionary must not contain any keys that trigger user interactions (for example, alerts, badges, or sounds).
The following is an example raw configuration object.
```
{
"APNS": "{\"aps\":{\"content-available\":1},\"Foo1\":\"Bar\",\"Foo2\":123}"
}
```
In this example, Amazon SNS sets the `apns-push-type` APNs header for the message to `background`. When Amazon SNS detects that the `apn` dictionary contains the `content-available` key set to `1`—and doesn't contain any other keys that can trigger user interactions—it sets the header to `background`.