South Korea SMS Guide - sms-compliance -

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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