Channels and failover
SMS, KakaoTalk AlimTalk, and automatic AlimTalk → SMS failover.
Pick the channel per request with channel (sms by default, or alimtalk). Message bodies come from registered templates; see Channels and templates.
SMS
Sent to any Korean mobile number. Use it when you do not have an approved AlimTalk template or when the user may not use KakaoTalk.
AlimTalk
Sent through an approved KakaoTalk business template. AlimTalk messages arrive in KakaoTalk and are usually read faster than SMS.
Automatic failover
When AlimTalk delivery fails (for example the recipient does not use KakaoTalk or the message is rejected), K-OTP automatically sends the same code by SMS. You do not need to call the API again, and the issueId stays the same, so verification works unchanged.
Cost
Every OTP send costs exactly 1 credit, whichever channel delivers it: SMS, AlimTalk, or AlimTalk with automatic SMS failover. A failover never costs a second credit.
Delivery status
GET /v1/status combines verification and delivery into one overallStatus, so your support team can see whether a code was queued, sent, delivered, or verified.