Send SMS, LMS and MMS in South Korea — code examples

Text messages need no template approval, so you can compose the body in code. That makes them the right tool for one-off notices and verification codes that no Alimtalk template covers.

Prerequisites

• A pre-registered SMS sending number (senderKey)
• An access key and secret key

No Kakao sender profile is needed.

SMS, LMS or MMS

Type	Body limit	Subject	Attachment	Use for
SMS	90 bytes (~45 Korean chars)	❌	❌	Verification codes, short alerts
LMS	2,000 bytes	✅	❌	Notices, long announcements
MMS	2,000 bytes	✅	Images	Event banners, coupon images

Byte counting: Korean characters are 2 bytes, Latin/digits/symbols 1, line breaks 1–2. If the body length varies at runtime, either use LMS from the start or branch on the measured length — going over 90 bytes means it cannot be sent as SMS.

Examples by language

Node.js / TypeScript

// SMS
await sendgo.sms.sendSms({
  content: '[Acme] Verification code: 123456 (valid 5 minutes)',
  contacts: [{ contact: '01012345678' }],
});

// LMS — long text with a subject
await sendgo.sms.sendLms({
  subject: '[Notice] Scheduled maintenance',
  content: `Hello,

Maintenance is scheduled.

- When: 2026-09-01 02:00 - 06:00 KST
- Scope: all services

Sorry for the inconvenience.`,
  contacts: [{ contact: '01012345678' }],
});

// MMS — with an image
await sendgo.sms.sendMms({
  subject: '[Event] September deals',
  content: 'Check out this month\'s offers!',
  contacts: [{ contact: '01012345678' }],
});

Python

client.sms.send_sms(
    content="[Acme] Verification code: 123456 (valid 5 minutes)",
    contacts=[{"contact": "01012345678"}],
)

client.sms.send_lms(
    subject="[Notice] Scheduled maintenance",
    content="Maintenance is scheduled for 2026-09-01 02:00-06:00 KST.",
    contacts=[{"contact": "01012345678"}],
)

client.sms.send_mms(
    subject="[Event] September deals",
    content="Check out this month's offers!",
    contacts=[{"contact": "01012345678"}],
)

PHP · Laravel

<?php

$sendgo->sms->sendSms([
    'content'  => '[Acme] Verification code: 123456 (valid 5 minutes)',
    'contacts' => [['contact' => '01012345678']],
]);

$sendgo->sms->sendLms([
    'subject'  => '[Notice] Scheduled maintenance',
    'content'  => "Maintenance is scheduled.\n\nWhen: 2026-09-01 02:00-06:00 KST",
    'contacts' => [['contact' => '01012345678']],
]);

In Laravel, either inject Sendgo or use app(Sendgo::class)->sms->sendSms([...]).

REST

curl -X POST https://sendgo.io/api/v2/messages/send \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "campaignType": "MESSAGE",
    "messageType": "SMS",
    "scheduleType": "DIRECTLY",
    "content": "Verification code: 123456",
    "contacts": [{ "contact": "01012345678" }],
    "senderKey": "your_sms_sender_key"
  }'

Switch messageType to LMS or MMS; both also take a subject.

Verification codes

The most common use, and the one with the sharpest failure mode.

const code = String(Math.floor(100000 + Math.random() * 900000));

await redis.setex(`verify:${phone}`, 300, code);   // 5 minute expiry

try {
  await sendgo.sms.sendSms({
    content: `[Acme] Verification code: ${code} (valid 5 minutes)`,
    contacts: [{ contact: phone }],
  });
} catch (error) {
  // Do not swallow this — the user is waiting for a message that will never arrive.
  throw new Error('Could not send the verification code. Please try again.');
}

• Do not swallow the failure. Unlike an order notification, a missing verification code blocks the user entirely.
• Rate limit resends. Without a per-number limit this becomes an SMS-bombing vector and drains your credit.
• Name your service in the body. People do not type codes from an unidentified sender.

Advertising rules

Promotional messages are regulated under the Network Act.

(광고)[Brand] Autumn sale, up to 50% off
...
Free opt-out 080-000-0000

• (광고) at the very start of the body
• A free opt-out number or method
• No sending between 21:00 and 08:00 KST
• Prior consent from every recipient

Verification codes and order notifications are informational and exempt.

Next

• Send a Kakao Alimtalk
• Error codes and retry strategy