Send SMS Messages with Zavu

SMS (Short Message Service) is the most universal messaging channel, reaching virtually any mobile phone without requiring an internet connection or app installation.

When to Use SMS

Verification codes: OTPs, 2FA
Transactional alerts: Order confirmations, shipping updates
Time-sensitive notifications: Appointment reminders
Universal reach: When you need to reach users without smartphones

Sending an SMS

const result = await zavu.messages.send({
  to: "+14155551234",
  text: "Your verification code is 123456",
  channel: "sms",
});

result = zavu.messages.send(
    to="+14155551234",
    text="Your verification code is 123456",
    channel="sms"
)

result = client.messages.send(
  to: "+14155551234",
  text: "Your verification code is 123456",
  channel: "sms"
)

result, _ := client.Messages.Send(context.TODO(), zavudev.MessageSendParams{
	To:      zavudev.String("+14155551234"),
	Text:    zavudev.String("Your verification code is 123456"),
	Channel: zavudev.String("sms"),
})

<?php
$result = $client->messages->send([
    'to' => '+14155551234',
    'text' => 'Your verification code is 123456',
    'channel' => 'sms',
]);

curl -X POST https://api.zavu.dev/v1/messages \
  -H "Authorization: Bearer $ZAVU_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "+14155551234",
    "text": "Your verification code is 123456",
    "channel": "sms"
  }'

You can optionally specify a sender by passing zavuSender (TypeScript), zavu_sender (Python), or the Zavu-Sender header (cURL). If omitted, your project’s default sender is used.

Message Length

SMS messages are limited to 160 characters (GSM-7 encoding) or 70 characters (Unicode). Longer messages are split into multiple segments.

Encoding	Single SMS	Concatenated SMS
GSM-7	160 chars	153 chars/segment
Unicode	70 chars	67 chars/segment

Keep messages under 160 characters when possible to avoid multi-segment charges.

Character Encoding

GSM-7 supports basic Latin characters. Using emojis, accents, or non-Latin scripts triggers Unicode encoding:

GSM-7:    "Your code is 123456"          (20 chars, 1 segment)
Unicode:  "Your code is 123456"         (22 chars, 1 segment with special chars)
Unicode:  "Tu codigo es 123456"           (19 chars, 1 segment, 'o' with accent triggers Unicode)

GSM-7 Character Set

A-Z a-z 0-9
@ $ _ ! " # % & ' ( ) * + , - . / : ; < = > ?
Space, newline, carriage return

Any character outside this set triggers Unicode encoding.

Sender ID

Some countries support alphanumeric sender IDs (e.g., “ZAVU” instead of a phone number).

Alphanumeric sender IDs cannot receive replies. Use a phone number if you need two-way SMS.

Supported Countries

Region	Alphanumeric Sender ID
US/Canada	Not supported (10DLC or short code required)
UK	Supported
EU	Mostly supported
LATAM	Varies by country

SMS Templates

Send pre-defined templates via SMS by specifying channel: "sms" and messageType: "template":

const result = await zavu.messages.send({
  to: "+14155551234",
  channel: "sms",
  messageType: "template",
  content: {
    templateId: "tpl_abc123",
    templateVariables: {
      "1": "John",
      "2": "ORD-12345",
    },
  },
});

curl -X POST https://api.zavu.dev/v1/messages \
  -H "Authorization: Bearer $ZAVU_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "+14155551234",
    "channel": "sms",
    "messageType": "template",
    "content": {
      "templateId": "tpl_abc123",
      "templateVariables": { "1": "John", "2": "ORD-12345" }
    }
  }'

If the template has an smsBody, it will be used instead of the default body. Contact variables like {{contact.first_name}} are automatically resolved from the recipient’s contact metadata.

Delivery Status

Check message status by ID:

curl https://api.zavu.dev/v1/messages/msg_abc123 \
  -H "Authorization: Bearer zv_live_xxx"

Status	Description
`queued`	Accepted, pending delivery
`sent`	Sent to carrier
`delivered`	Confirmed delivered
`failed`	Delivery failed

Common Errors

Error Code	Description	Solution
`30003`	Unreachable destination	Invalid number or phone off
`30004`	Message blocked	Content filtered by carrier
`30005`	Unknown destination	Number doesn’t exist
`30006`	Landline destination	Cannot send SMS to landlines
`30007`	Carrier violation	Message rejected by carrier

Compliance

SMS messaging is regulated. Ensure you have consent before sending messages.

Requirements

Opt-in consent: Users must explicitly agree to receive SMS
Opt-out mechanism: Include instructions to unsubscribe (e.g., “Reply STOP to unsubscribe”)
Business identification: Identify your business in the message
Time restrictions: Avoid sending during quiet hours (typically 9 PM - 9 AM local time)

Example Compliant Message

[YourBrand] Your order #12345 has shipped! Track: https://track.co/abc

Reply STOP to unsubscribe

Best Practices

Keep it short - Aim for under 160 characters
Identify yourself - Start with your brand name
Be actionable - Include clear next steps or links
Respect timing - Send during business hours in the recipient’s timezone
Provide opt-out - Always include unsubscribe instructions for marketing messages

Getting Started

Concepts

Guides

Send SMS Messages with Zavu

When to Use SMS

Sending an SMS

Message Length

Character Encoding

GSM-7 Character Set

Sender ID

Supported Countries

SMS Templates

Delivery Status

Common Errors

Compliance

Requirements

Example Compliant Message

Best Practices

​When to Use SMS

​Sending an SMS

​Message Length

​Character Encoding

​GSM-7 Character Set

​Sender ID

​Supported Countries

​SMS Templates

​Delivery Status

​Common Errors

​Compliance

​Requirements

​Example Compliant Message

​Best Practices

When to Use SMS

Sending an SMS

Message Length

Character Encoding

GSM-7 Character Set

Sender ID

Supported Countries

SMS Templates

Delivery Status

Common Errors

Compliance

Requirements

Example Compliant Message

Best Practices