Messaging Channels: SMS, Viber, and WhatsApp Guide

SmsManager supports four messaging channels, each with its own strengths and configuration options. You can use a single channel or combine them in a message flow to maximize delivery rates. This page covers what each channel can do, what fields it accepts, and how to set it up.

SMS
Viber
WhatsApp Text
WhatsApp Template

SMS channel

SMS is the most universally supported channel — it works on every mobile phone, requires no app installation, and is available in virtually every country. Use SMS as a reliable standalone channel or as the final fallback in a multi-channel flow.

Required fields

Field	Type	Description
`body`	string	The message text (max 1,000 chars).

Optional fields

Field	Type	Default	Description
`sender`	string	—	Alphanumeric sender name (max 11 characters) or a dedicated virtual number without the leading `+`. Pre-registration may be required for alphanumeric senders.
`gateway`	string	`high`	Routing gateway. Use `high` for standard delivery, `direct` when sending from a dedicated virtual number, or `custom` for SIM hosting setups.
`ttl`	integer	—	Time to live in minutes. If the message can’t be delivered within this window, it’s discarded.
`type`	string	`utf`	Character encoding. `utf` preserves Unicode characters (emoji, Cyrillic, etc.). `sms` strips or converts Unicode to maximise the number of characters per SMS part.

Unicode and message length

Standard SMS parts hold up to 160 GSM-7 characters. When you use type: utf and include Unicode characters, each part shrinks to 70 characters. Keep this in mind for messages near the part boundary — a long message that’s fine as plain text may split into more parts once emoji are added.

Gateway guide

high — Default shared gateway, suitable for the vast majority of SMS sends.
direct — Use this when you’ve purchased a dedicated virtual number and want two-way messaging. Set sender to your virtual number (without +).
custom — Use this when you’re using SIM-card hosting. Contact SmsManager support to configure this gateway.

Example

{
  "body": "Your one-time code is 8274. Valid for 10 minutes.",
  "to": [{ "phone_number": "420777123456" }],
  "flow": [
    {
      "sms": {
        "sender": "MyCompany",
        "gateway": "high",
        "type": "sms",
        "ttl": 10
      }
    }
  ]
}

Viber channel

Viber Business Messages let you send rich content — longer text, a call-to-action button, and brand-registered sender names — directly in the Viber app. Viber messages are typically cheaper than SMS and support a richer user experience, but they require the recipient to have Viber installed.

Required fields

Field	Type	Description
`body`	string	The message text (max 1,000 chars).
`sender`	string	The pre-registered Viber Business sender name. Must match exactly the name registered through SmsManager.

Optional fields

Field	Type	Default	Description
`ttl`	integer	—	Time to live in minutes. If the message isn’t delivered before the TTL expires, SmsManager moves to the next channel in the flow.
`buttons`	array	—	Up to one button. Each button object requires a `title` (button label) and a `url` (destination URL).

Setup requirements

Before you can send Viber Business Messages, you need to register a Viber Business sender name through SmsManager. The name must be approved by Viber and is typically your brand or company name. Contact SmsManager support or visit your account dashboard to begin registration.

Example

{
  "body": "Your order #5821 is ready for pickup! 🎉",
  "to": [{ "phone_number": "420777123456" }],
  "flow": [
    {
      "viber": {
        "sender": "MyShop",
        "ttl": 120,
        "body": "Your order #5821 is ready for pickup! 🎉",
        "buttons": [
          {
            "title": "View order",
            "url": "https://example.com/orders/5821"
          }
        ]
      }
    },
    {
      "sms": {
        "sender": "MyShop",
        "body": "Your order #5821 is ready for pickup!"
      }
    }
  ]
}

Viber Business Messages are only delivered to recipients who have the Viber app installed. Always include an SMS fallback in your flow to reach recipients who don’t use Viber.

WhatsApp text channel

WhatsApp text messages let you send a free-form message body over WhatsApp — the same kind of message a person would type. Because WhatsApp restricts unsolicited outbound messaging, you can only send a free-form text message within the 24-hour customer service window: a window that opens when the recipient sends you a message first or replies to one of your WhatsApp template messages.

Required fields

Field	Type	Description
`body`	string	The message text (max 1,000 chars). Only allowed within the 24-hour customer service window.
`sender`	string	The Phone Number ID of your registered WhatsApp number.

Setup requirements

You must connect a WhatsApp Business phone number to your SmsManager account before you can send WhatsApp messages. Find your Phone Number ID in your WhatsApp settings at app.smsmanager.com/whatsapp.

When to use WhatsApp text vs. WhatsApp template

Situation	Use
Recipient has messaged you or replied to a template in the last 24 hours	`whatsapp_text`
Initiating proactive contact (the recipient hasn’t written to you recently)	`whatsapp_template`

Example

{
  "to": [{ "phone_number": "420777123456" }],
  "flow": [
    {
      "whatsapp_text": {
        "sender": "514578330250514",
        "body": "Thanks for reaching out! Here's the info you requested: https://example.com/faq"
      }
    }
  ]
}

If you attempt to send a whatsapp_text message outside the 24-hour customer service window, the channel will fail and SmsManager will move to the next channel in your flow. Use whatsapp_template for proactive outreach.

WhatsApp template channel

WhatsApp template messages let you initiate proactive contact with any recipient — even if they’ve never messaged you before. Templates are pre-approved by Meta and contain fixed structural text with optional variable placeholders. Because they’re pre-vetted, you can send them at any time, not just within a customer service window.

Required fields

Field	Type	Description
`template_name`	string	The exact name of the approved template (max 100 chars).
`sender`	string	The Phone Number ID of your registered WhatsApp number.
`language`	string	The language code for the template version to use (e.g., `en`, `cs`, `de`).

Optional fields

Field	Type	Description
`params`	array of strings	Values for the variable placeholders in the template body (in order).
`params_header`	array of strings	Value for the variable placeholder in the template header, if present.
`params_buttons`	array of strings	Values for variable placeholders in template buttons (e.g., dynamic URLs).
`ttl`	integer	Time to live in minutes.

Setup requirements

Connect a WhatsApp Business number — visit app.smsmanager.com/whatsapp to link your number and retrieve your Phone Number ID.
Create and approve a template — templates must be submitted to and approved by Meta before use. This process typically takes a few minutes to a few hours.

Example

{
  "to": [{ "phone_number": "420777123456" }],
  "flow": [
    {
      "whatsapp_template": {
        "sender": "514578330250514",
        "template_name": "order_confirmation",
        "language": "en",
        "params": ["John", "ORD-9921"],
        "params_header": ["ORD-9921"],
        "params_buttons": ["https://example.com/track/ORD-9921"],
        "ttl": 1440
      }
    },
    {
      "sms": {
        "sender": "MyShop",
        "body": "Hi John, your order ORD-9921 is confirmed! Track: https://example.com/track/ORD-9921"
      }
    }
  ]
}

In this example the template body might read: “Hi , your order is confirmed!” — params supplies the values ["John", "ORD-9921"] in order.

If the template hasn’t been approved yet or the approval has been revoked, the whatsapp_template channel will fail and SmsManager will fall back to the next channel in your flow.

​SMS channel

​Required fields

​Optional fields

​Unicode and message length

​Gateway guide

​Example

​Viber channel

​Required fields

​Optional fields

​Setup requirements

​Example

​WhatsApp text channel

​Required fields

​Setup requirements

​When to use WhatsApp text vs. WhatsApp template

​Example

​WhatsApp template channel

​Required fields

​Optional fields

​Setup requirements

​Example

SMS channel

Required fields

Optional fields

Unicode and message length

Gateway guide

Example

Viber channel

Required fields

Optional fields

Setup requirements

Example

WhatsApp text channel

Required fields

Setup requirements

When to use WhatsApp text vs. WhatsApp template

Example

WhatsApp template channel

Required fields

Optional fields

Setup requirements

Example