Japan SMS Best Practices, Compliance, and Features

Japan SMS Market Overview

Locale name:	Japan
ISO code:	JP
Region	Asia
Mobile country code (MCC)	440
Dialing Code	+81

Market Conditions: Japan has a highly developed mobile market dominated by three major carriers: NTT DOCOMO, KDDI (au), and SoftBank. While OTT messaging apps like LINE are extremely popular for personal communications, SMS remains critical for business communications, particularly for authentication, notifications, and customer service. The market shows strong preference for iOS devices, though Android maintains significant presence. SMS delivery rates are notably high due to robust infrastructure and strict regulatory compliance.

Key SMS Features and Capabilities in Japan

Japan offers comprehensive SMS capabilities with support for two-way messaging, concatenation, and strict regulatory compliance requirements across all major carriers.

Two-way SMS Support

Yes, Japan fully supports two-way SMS communications. This enables interactive messaging scenarios like customer service, appointment confirmations, and automated responses. No special restrictions apply beyond standard compliance requirements.

Concatenated Messages (Segmented SMS)

Support: Yes, concatenation is supported across all major Japanese carriers, though support may vary by sender ID type.
Message length rules: Standard 160 characters per message segment using GSM-7 encoding. Messages exceeding this limit are automatically concatenated.
Encoding considerations: Both GSM-7 and UCS-2 encodings are supported. For Japanese characters (Kanji, Hiragana, Katakana), UCS-2 encoding is used, reducing the character limit to 70 per segment.

MMS Support

MMS is not available in Japan through standard SMS channels. Any MMS content must be converted to SMS with a URL link to the media content. Best practice is to use short URLs and clearly indicate when a link leads to media content.

Recipient Phone Number Compatibility

Number Portability

Number portability is fully available in Japan across all major carriers. This allows users to keep their phone numbers when switching providers. While this doesn't significantly affect SMS delivery or routing, proper formatting of phone numbers (+81 format) is essential for reliable delivery.

Sending SMS to Landlines

Sending SMS to landline numbers is not supported in Japan. Attempts to send SMS to landline numbers will result in delivery failure with a 400 response error (code 21614). Messages will not appear in logs and accounts will not be charged for failed attempts.

Compliance and Regulatory Guidelines for SMS in Japan

SMS communications in Japan are regulated by the Ministry of Internal Affairs and Communications (MIC) and the Personal Information Protection Commission (PPC). Businesses must comply with the Act on Regulation of Transmission of Specific Electronic Mail and the Personal Information Protection Act (PIPA). These regulations govern how companies can collect, use, and protect personal information, including phone numbers.

Explicit Consent Requirements:

Written or digital consent must be obtained before sending any marketing messages
Consent records must be maintained and easily accessible
Purpose of communication must be clearly stated during opt-in
Double opt-in is strongly recommended for marketing messages

Best Practices for Documentation:

Store timestamp and source of consent
Maintain detailed records of opt-in method and context
Keep consent records for at least 2 years
Regular audit of consent database

HELP/STOP and Other Commands

All messages must include opt-out instructions in Japanese
Standard keywords must be supported:
- STOP (停止)
- HELP (ヘルプ)
- CANCEL (解約)
Commands must work in both English and Japanese
Response to HELP/STOP must be immediate and in Japanese

Do Not Call / Do Not Disturb Registries

Japan maintains a Do Not Call registry managed by the Japan Data Communications Association (JDCA).

Businesses must check numbers against the registry monthly
Maintain internal suppression lists
Honor opt-out requests within 24 hours
Regular database cleaning recommended to remove inactive numbers

Time Zone Sensitivity

Sending Hours:

Restricted to 9:00 AM - 8:00 PM JST
Emergency messages exempt from time restrictions
Respect national holidays and weekends
Consider regional time differences for international businesses

Phone Numbers Options and SMS Sender Types for Japan

Alphanumeric Sender ID

Operator network capability: Supported through both international and domestic gateways
Registration requirements:

International: No pre-registration required
Domestic: Mandatory registration with 5-week approval process
Sender ID preservation: Not preserved for domestic gateway; preserved for international gateway

Long Codes

Domestic vs. International:

Domestic: Not supported
International: Fully supported
Sender ID preservation: Yes, for international long codes
Provisioning time: Immediate for international numbers
Use cases:
Two-way communication
Customer service
Transactional messages

Short Codes

Support: Available through domestic gateway only
Provisioning time: 5-8 weeks for approval
Use cases:

High-volume marketing campaigns
Two-factor authentication
Customer loyalty programs

Restricted SMS Content, Industries, and Use Cases

Prohibited Content:

Firearms and weapons
Gambling and betting
Adult content
Money lending/loan services
Lead generation
Political messages
Religious content
Controlled substances
Cannabis products
Alcohol-related content

Additional Restrictions:

Phone numbers in message content not allowed
M2M messaging supported on best-effort basis only

Content Filtering

Carrier Filtering Rules:

URLs must be from approved domains
No excessive punctuation or special characters
Message length restrictions vary by carrier
KDDI limits messages to 5 segments

Tips to Avoid Blocking:

Use approved URL shorteners
Avoid spam trigger words
Maintain consistent sending patterns
Include clear company identification

Best Practices for Sending SMS in Japan

Messaging Strategy

Keep messages under 70 characters when using Japanese text
Include clear call-to-action
Maintain consistent sender ID
Use polite, formal Japanese language style

Sending Frequency and Timing

Limit to 1-2 messages per day per recipient
Respect Japanese holidays and observances
Avoid sending during early morning or late evening
Space out bulk sends to prevent network congestion

Localization

Default to Japanese language unless recipient specifies otherwise
Use proper honorifics and formal business Japanese
Consider cultural context and sensitivities
Support both Japanese and English response handling

Opt-Out Management

Process opt-outs within 24 hours
Maintain centralized opt-out database
Confirm opt-out with one final message
Regular cleanup of contact lists

Testing and Monitoring

Test across all major carriers (NTT DOCOMO, KDDI, SoftBank)
Monitor delivery rates by carrier
Track opt-out rates and patterns
Regular testing of HELP/STOP functionality

SMS API integrations for Japan

Twilio

Twilio provides robust SMS capabilities for the Japanese market through their REST API. Authentication uses account SID and auth token credentials.

Key Parameters:

to: Japanese phone numbers in E.164 format (+81XXXXXXXXXX)
from: Your Twilio phone number or approved sender ID
body: Message content (supports Unicode for Japanese characters)

import * as twilio from 'twilio';

// Initialize Twilio client with credentials
const client = twilio(
  process.env.TWILIO_ACCOUNT_SID,
  process.env.TWILIO_AUTH_TOKEN
);

async function sendJapaneseSMS() {
  try {
    // Send SMS with Japanese text support
    const message = await client.messages.create({
      body: 'こんにちは！このメッセージはテストです。', // Japanese text
      from: process.env.TWILIO_PHONE_NUMBER,
      to: '+81XXXXXXXXXX' // Japanese phone number
    });
    
    console.log(`Message sent successfully: ${message.sid}`);
  } catch (error) {
    console.error('Error sending message:', error);
  }
}

Sinch

Sinch offers direct carrier connections in Japan with support for both Latin and Japanese character sets.

import { SinchClient } from '@sinch/sdk-core';

// Initialize Sinch client
const sinchClient = new SinchClient({
  projectId: process.env.SINCH_PROJECT_ID,
  keyId: process.env.SINCH_KEY_ID,
  keySecret: process.env.SINCH_KEY_SECRET
});

async function sendSMS() {
  try {
    const response = await sinchClient.sms.batches.send({
      sendSMSRequestBody: {
        to: ['+81XXXXXXXXXX'],
        from: 'YourCompany', // Alphanumeric sender ID
        body: 'メッセージの内容',
        encoding: 'UCS2' // Required for Japanese characters
      }
    });
    
    console.log('Message sent:', response.id);
  } catch (error) {
    console.error('Failed to send message:', error);
  }
}

MessageBird

MessageBird provides high-quality routes to Japanese carriers with support for Unicode messages.

import { MessageBird } from 'messagebird';

// Initialize MessageBird client
const messagebird = new MessageBird(process.env.MESSAGEBIRD_API_KEY);

// Configure message parameters
const params = {
  originator: 'COMPANY',
  recipients: ['+81XXXXXXXXXX'],
  body: '確認コード: 123456',
  type: 'unicode' // Enable Japanese character support
};

// Send message
messagebird.messages.create(params, (err, response) => {
  if (err) {
    console.error('Error:', err);
    return;
  }
  console.log('Message sent:', response.id);
});

Plivo

Plivo offers direct connectivity to Japanese carriers with support for long codes and alphanumeric sender IDs.

import plivo from 'plivo';

// Initialize Plivo client
const client = new plivo.Client(
  process.env.PLIVO_AUTH_ID,
  process.env.PLIVO_AUTH_TOKEN
);

async function sendPlivoSMS() {
  try {
    const response = await client.messages.create({
      src: 'COMPANY', // Your sender ID
      dst: '+81XXXXXXXXXX', // Destination number
      text: 'ご確認ください。', // Message text
      url_strip_query_params: false // Preserve URL parameters if included
    });
    
    console.log('Message sent with UUID:', response.messageUuid);
  } catch (error) {
    console.error('Failed to send message:', error);
  }
}

API Rate Limits and Throughput

Rate Limits:

KDDI: 5 segments maximum per message
General carrier limits: 30 messages per second
Daily volume limits vary by provider and sender type

Throughput Management:

Implement exponential backoff for retries
Use queuing systems (Redis, RabbitMQ) for high volume
Batch messages when possible
Monitor delivery receipts for rate adjustments

Error Handling and Reporting

Implement comprehensive logging with correlation IDs
Monitor delivery receipts (DLRs) for status tracking
Set up alerts for unusual error rates
Store message metadata for troubleshooting
Regular audit of delivery performance by carrier

Recap and Additional Resources

Key Takeaways:

Obtain explicit consent before sending messages
Support both Japanese and English opt-out commands
Respect sending hours (9 AM - 8 PM JST)
Use proper character encoding for Japanese text
Monitor delivery rates and optimize sending patterns

Next Steps:

Review MIC guidelines for SMS communications
Implement proper consent management systems
Set up monitoring and reporting infrastructure
Test message delivery across all major carriers

Additional Information:

Industry Resources:

KDDI Business SMS Guidelines
NTT DOCOMO Enterprise Messaging Documentation
SoftBank Corporate Messaging Standards

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