Send a Message

Use this endpoint to send text, media, or template-based messages across SMS, WhatsApp, Messenger, and RCS.

Most message types support personalisation using injected_fields, allowing you to dynamically insert values into message text.

WhatsApp Template Messages use template parameters, which must match the placeholder structure of the Meta-approved template.

• Supports text messages
• Supports personalisation via injected_fields
• No template approval required
• Media not supported

• Supports text, media, and approved Templates
• Business-initiated messages must use a WhatsApp Template
• Free-form messages allowed only within the 24-hour customer service window
• Supports delivered and read receipts

• Supports text & media
• Business cannot initiate the conversation — the customer must message first
• Supports read receipts

• Supports text, image, video, file and custom (rich cards, carousels, suggested replies)
• Templates and audio are not supported
• Sent from your verified RCS agent; no sender field
• Business may initiate conversations
• See Getting Started – RCS

curl -X POST "POST https://api.instamessage.com/v1/messages" \
  -H "Authorization: Bearer $IM_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "sms",
    "to": "+447123456789",
    "message_type": "text",
    "text": "Your delivery is on its way."
  }'

{
  "channel": "sms",
  "to": "+447123456789",
  "message_type": "text",
  "text": "Hi {{name}}, your parcel {{tracking}} is out for delivery.",
  "injected_fields": {
    "name": "Alex",
    "tracking": "ZX123456"
  }
}

{
  "channel": "whatsapp",
  "to": "+447123456789",
  "message_type": "image",
  "image": { "url": "https://example.com/photo.jpg" }
}

Note: free-form WhatsApp messages can only be sent within the 24-hour customer session window.

{
  "channel": "whatsapp",
  "to": "+447123456789",
  "message_type": "template",
  "template": {
    "name": "order_confirmation",
    "parameters": ["Alex", "12345"]
  }
}

{
  "channel": "rcs",
  "to": "+447123456789",
  "message_type": "custom",
  "custom": {
    "contentMessage": {
      "text": "Your delivery is booked for tomorrow. Does that work?",
      "suggestions": [
        { "reply": { "text": "Yes, thanks", "postbackData": "CONFIRM" } }
      ]
    }
  }
}

See Rich messages for rich cards, carousels and limits.

{
  "channel": "messenger",
  "to": "+447123456789",
  "message_type": "image",
  "image": { "url": "https://example.com/menu.png" }
}

Injected fields allow you to replace placeholders inside your message text with real values at send time.

{
  "channel": "sms",
  "to": "+447123456789",
  "message_type": "text",
  "text": "Hello {{firstname}}, your booking {{bookingId}} is confirmed.",
  "injected_fields": {
    "firstname": "Sam",
    "bookingId": "BR-128547"
  }
}

WhatsApp Template Messages use template parameters, not injected_fields.

{
  "message_id": "msg_67890",
  "status": "queued",
  "created_at": "2025-06-01T14:22:00Z"
}

Common errors

• Invalid phone number format
• Unsupported message_type for channel
• Messenger outbound attempted without prior inbound
• WhatsApp free-form sent outside 24-hour window
• Missing template parameters
• RCS custom content breaks a rich content limit (4044)
• Incorrect JSON structure

• Delivery tracking → Delivery Receipts & Message Status
• Customer replies → Inbound Messages & Replies
• Webhooks → Webhook Quick-Start
• Managing Templates → WhatsApp Templates