Send Multiple Transactional SMS with OAuth 2.0

You can use this endpoint to send up to 50 SMS messages in a single request. Each message is validated and processed independently; the response reports per-message acceptance and per-message validation errors.

Use Cases

You can send transactional SMS messages for:

System notifications, password reset messages, and login codes
Order confirmations, shipping updates, and delivery alerts
Appointment confirmations and ticket booking confirmations
Welcome messages and recurring billing notifications

Endpoint and Headers

POST https://gw.useinsider.com/api/sms/v1/sendMultipleMessage

Visit our Postman collection to test this request.

Headers

Header	Sample Value	Description
Authorization	Bearer	Bearer access token obtained from the /auth/token endpoint. This key is required to authorize your request. Refer to Generate an OAuth 2.0 Token for SMS to generate your OAuth 2.0 token.
Content-Type	application/json	Specifies the media type of the request body.

Body Parameters

Parameter	Description	Data Type	Required
sender	Default sender for all messages in the batch.	String	No
messages	Array of message objects. Minimum 1 entry, maximum 50 entries.	Array (Object)	Yes

Message Object

Parameter	Description	Data Type	Required
phoneNumber	Recipient phone number in E.164 format.	String	Yes
content	SMS body. Length between 1 and 670 characters.	String	Yes
callback	Per-message webhook URL for delivery events.	URL	No
sendAt	Per-message ISO 8601 schedule timestamp.	String	No
uniqueArgs	Per-message correlation metadata.	Object	No
settings	Per-message send-time options.	Object	No

Sample Request

curl --location 'https://gw.useinsider.com/api/sms/v1/sendMultipleMessage' \
  --header 'Authorization: Bearer eyJhbGc...' \
  --header 'Content-Type: application/json' \
  --data '{
    "sender": "BRAND_SMS",
    "messages": [
      { "phoneNumber": "+905551234567", "content": "Hi Ahmet, your order has shipped.", "uniqueArgs": { "userId": "u-1" } },
      { "phoneNumber": "+905557654321", "content": "Hi Ayse, your order has shipped.",  "uniqueArgs": { "userId": "u-2" } }
    ]
  }'

Sample Responses

202 All Accepted

{
  "message": "Accepted",
  "messageIds": [
    { "phoneNumber": "+905551234567", "messageId": "sms-a..." },
    { "phoneNumber": "+905557654321", "messageId": "sms-b..." }
  ]
}

201: Partially Accepted

When some messages pass validation, and others don't, the API returns 201 with both successful message IDs and per-message errors.

{
  "message": "Accepted",
  "messageIds": [
    { "phoneNumber": "+905551234567", "messageId": "sms-a..." }
  ],
  "errors": [
    { "field": "messages[1].phoneNumber", "error": "must be a valid phone number" }
  ]
}

400: All Rejected

{
  "message": "Failed to validate request",
  "errors": [
    { "field": "messages[0].content",     "error": "is required" },
    { "field": "messages[1].phoneNumber", "error": "must be a valid phone number" }
  ]
}

Batch-Specific Error Responses

{ "message": "Maximum 50 messages are allowed", "errorCode": "1017" }

For other error codes, refer to the table below.

errorCode	HTTP	Description
1000	400	Invalid JSON content supplied (single send).
1001	400	Request body failed validation. Per-field errors are included in the response.
1004	400	Country quota lookup failed, or the message content domain is not allowed for this account.
1011	400	Invalid JSON content supplied (batch send).
1017	400	Batch exceeds 50 messages.
1015	500	Provider maintenance mode is active. Retry later.
1022	403	Your panel is suspended.
1024	403	Your panel is deactivated.
1025	403	Transactional messaging is disabled on your account.
1016	403	The specified sender was not found or is inactive.
1018	403	Sender provider settings are missing or invalid.

Limitations

Requests made with the sms-transactional scope are limited to 60,000 requests per 60 seconds, with a burst limit of 1,000 requests.
If the limit is exceeded, the API returns a 429 Too Many Requests response with a Retry-After header indicating when you can retry the request.
SMS body must be between 1 and 670 characters.
Emojis and non-GSM-7 characters switch the encoding to UCS-2, which uses 70 characters per segment instead of 160. Use smartEncoding to automatically convert common characters.
Request body size is capped at ~19.9 MB.
Batch sends are capped at 50 messages per request.

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