Frequently Asked Questions
Use a reputable SMS API provider like Twilio, Sinch, or Bird, ensuring your messages are encoded in EUC-KR for Korean characters and comply with local regulations. Due to the lack of two-way SMS support for A2P messaging, businesses must use one-way messaging and alternative channels for customer responses.
Despite the popularity of OTT apps like KakaoTalk, SMS remains essential for business communication in South Korea. It's primarily used for authentication, notifications, and marketing, particularly given the country's near 100% smartphone penetration.
South Korea's regulations prohibit two-way A2P SMS to prevent spam and ensure security. Businesses must use one-way SMS and other channels for customer interactions.
One SMS segment can hold up to 140 bytes, which translates to 140 ASCII characters or 70 Unicode characters. Messages must also be encoded using EUC-KR for Korean text.
Adhere to the standard sending window of 8:00 AM to 9:00 PM KST, avoid major holidays, and limit frequency to 1-2 messages per recipient daily. B2B communications should ideally occur during business hours (9:00 AM - 6:00 PM).
Obtain explicit written or electronic consent before sending marketing SMS, stating the purpose, frequency, and type of messages. Maintain these records for at least 3 years and consider double opt-in verification.
No, alphanumeric sender IDs are not supported in South Korea. All sender IDs are converted to numeric format by carriers, regardless of the original format.
All marketing messages must include opt-out instructions in Korean. Process requests within 24 hours, maintain a centralized opt-out database, and confirm the opt-out status to users.
Sending SMS messages to landline numbers in South Korea is not possible. Attempts will result in a 400 response error (code 21614), and no charge will occur.
Prohibited content includes gambling, adult material, political campaigns, cryptocurrency promotions, and unauthorized pharmaceutical products. Financial and healthcare industries face additional regulations.
Use registered sender IDs, avoid URL shorteners, include mandatory prefixes (like [Web ??????] for A2P), and keep content clear, professional, and compliant with character set (EUC-KR) requirements.
Comply with KCC and KISA regulations, including the Personal Information Protection Act (PIPA), obtain consent for marketing messages, provide clear opt-out instructions, and respect sending time restrictions.
MMS messages are automatically converted to SMS with an embedded URL link. This ensures compatibility across all carriers while still allowing for the sharing of rich media content via a web link.
Short codes are not supported for international businesses in South Korea. Businesses need to use long codes with specific prefixes.
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South Korea SMS Best Practices, Compliance, and Features
South Korea SMS Market Overview
Market Conditions: South Korea has one of the world's most advanced mobile markets, with nearly 100% smartphone penetration. The market is dominated by three major mobile operators: SK Telecom, KT (Korea Telecom), and LG U+. While OTT messaging apps like KakaoTalk are extremely popular for personal communications, SMS remains crucial for business communications, particularly for authentication, notifications, and marketing. Android devices hold approximately 70% market share, with iOS devices making up most of the remainder.
Key SMS Features and Capabilities in South Korea
South Korea maintains strict regulations on SMS capabilities, with specific requirements for message formatting, sender IDs, and delivery mechanisms to ensure security and prevent spam.
Two-way SMS Support
Two-way SMS is not supported in South Korea for A2P (Application-to-Person) messaging. Businesses must use one-way messaging for their communications, with alternative channels required for customer responses.
Concatenated Messages (Segmented SMS)
Support: Concatenated messages are no longer supported by most carriers, with SK Telecom being the only exception.
Message length rules: One SMS segment can contain up to 140 bytes, equivalent to 140 ASCII characters or 70 Unicode characters.
Encoding considerations: Messages support both GSM-7 (ASCII) and UCS-2 (Unicode) encoding, but must use EUC-KR encoding for Korean characters.
MMS Support
MMS messages are automatically converted to SMS with an embedded URL link. This ensures compatibility across all carriers while still allowing rich media content to be shared through a web-based approach.
Recipient Phone Number Compatibility
Number Portability
Number portability is available in South Korea, allowing users to keep their phone numbers when switching carriers. This feature does not significantly impact message delivery or routing as the infrastructure is well-established.
Sending SMS to Landlines
Sending SMS to landline numbers is not possible in South Korea. Attempts to send messages to landline numbers will result in a 400 response error (code 21614), and the message will not be delivered or charged to the account.
Compliance and Regulatory Guidelines for SMS in South Korea
SMS communications in South Korea are regulated by the Korea Communications Commission (KCC) and Korea Internet & Security Agency (KISA). Organizations must comply with the Personal Information Protection Act (PIPA) and the Act on Promotion of Information and Communications Network Utilization and Information Protection.
Consent and Opt-In
Explicit Consent Requirements:
Best Practices for Consent:
HELP/STOP and Other Commands
Do Not Call / Do Not Disturb Registries
Time Zone Sensitivity
Phone Numbers Options and SMS Sender Types for in South Korea
Alphanumeric Sender ID
Operator network capability: Not supported Registration requirements: N/A Sender ID preservation: All sender IDs are converted to numeric format
Long Codes
Domestic vs. International:
Sender ID preservation: No, international numbers are modified with country prefix Provisioning time: 3-5 business days Use cases: Transactional messages, alerts, notifications
Short Codes
Support: Not supported for international businesses Provisioning time: N/A Use cases: N/A
Restricted SMS Content, Industries, and Use Cases
Prohibited Content:
Regulated Industries:
Content Filtering
Carrier Filtering Rules:
Tips to Avoid Blocking:
Best Practices for Sending SMS in South Korea
Messaging Strategy
Sending Frequency and Timing
Localization
Opt-Out Management
Testing and Monitoring
SMS API integrations for South Korea
Twilio
Twilio provides a robust SMS API with specific support for South Korean messaging requirements.
Sinch
Sinch offers dedicated APIs for the South Korean market with built-in compliance handling.
Bird
Bird's API provides streamlined integration for South Korean messaging compliance.
API Rate Limits and Throughput
Throughput Management Strategies:
Error Handling and Reporting
Common Error Scenarios:
Best Practices:
Recap and Additional Resources
Key Takeaways:
Next Steps:
Additional Resources: