Introduction

K-OTP lets you issue → deliver → verify phone verification codes (OTP) with two API calls. K-OTP generates the code, sends it by KakaoTalk AlimTalk (with an SMS fallback, on by default), enforces expiry and attempt limits, deduplicates retries, and settles credits.

How it works

 Your server / browser          K-OTP API                     End user's phone
 ─────────────────────          ─────────                     ────────────────
 1. POST /v1/issue  ─────────▶  generate 6-digit code (hash only)
    (Idempotency-Key)           reserve credit + queue delivery
                     ◀───────── { issueId, expiresAt, ... }
                                2. AlimTalk (SMS fallback) ──▶  "[K-OTP] 인증번호는 123456..."
 3. POST /v1/verify ─────────▶  check issueId + code
    { issueId, code }           (expiry, max attempts, one-time)
                     ◀───────── { verified: true }

1. Issue — your service sends a phone number and a purpose to POST /v1/issue. K-OTP generates a 6-digit code server-side, reserves credit, and queues delivery. The response contains an issueId, never the code.
2. Deliver — K-OTP sends the code by KakaoTalk AlimTalk and automatically falls back to SMS if AlimTalk fails (you can turn the fallback off per request). Delivery is tracked asynchronously; check it with GET /v1/status.
3. Verify — send the code the user typed together with the issueId to POST /v1/verify. The response is always 200; read verified and, on failure, reasonCode.

Key concepts

URLs

Next steps