Send a verification code

Generate a one-time code, deliver it to the recipient, and store only its hash. Check the user-typed code with POST /v1/verify/verifications/{verificationId}/check.

Re-POSTing for the same (channel, to) while a verification is active RESENDS a fresh code on the existing verification (200 with resend: true) instead of creating a new one; resends are limited to one per 60 seconds (429 with retryAfterSeconds inside the cooldown). The stored brandName/codeLength/ttlMinutes win on a resend.

Codes deliver from a number on your account (from optional when you own exactly one number on the channel), always with a fixed template:

• sms: from an SMS-enabled number. Each accepted send bills one verification fee plus the standard message rate.
• whatsapp: from a connected WhatsApp number, as a Meta AUTHENTICATION template with a copy-code button. The first WhatsApp verification on a WhatsApp Business Account creates the zernio_verify_code template there and answers 422 template_pending until Meta approves it (usually minutes; retry after retryAfterSeconds). Meta fixes the message text, so brandName is not shown and the code's validity is not stated in the message (ttlMinutes is still enforced). Each accepted send bills one verification fee; Meta bills its authentication rate to your WhatsApp Business Account.