Phone Verification API — Send OTP Codes via iMessage or SMS
Deliver verification codes in under a second via iMessage, with automatic SMS fallback. No carrier registration required.
The Problem
SMS OTP via traditional APIs like Twilio takes 3–5 seconds to deliver and costs $0.0079 per message — plus monthly number fees and 10DLC campaign registration fees on top. By the time your code arrives, users are already clicking "resend."
10DLC registration adds $15–25 per campaign and weeks of approval time before you can send a single verification code. If your use case doesn't fit neatly into a pre-approved category, you're stuck waiting with no clear timeline.
SMS-only delivery means lower open rates, no read receipts, and no delivery confirmation you can act on. When a code fails silently, your user thinks your product is broken — not the carrier.
The senderZ Solution
senderZ routes OTP codes via iMessage first — which arrives in approximately one second — and automatically falls back to SMS if the recipient doesn't have iMessage. You call one endpoint, senderZ handles the rest.
No 10DLC registration. No carrier approval. No per-number monthly fees layered on top of per-message costs. One API, one price, fastest possible delivery.
curl -X POST https://api.senderz.com/v1/messages \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"to": "+15551234567",
"channel": "auto",
"template": "otp_verify",
"data": {
"code": "4821",
"app_name": "Acme",
"minutes": "10"
}
}'Not a developer? senderZ Simple Mode lets you send messages, manage contacts, and run campaigns without writing a single line of code. See plans and pricing →
Key Features
- Sub-second delivery — iMessage OTPs arrive almost instantly, compared to 3–5 seconds over SMS. Faster verification means less drop-off in your sign-up flow.
- High-priority queue — OTP messages are marked as high priority and skip ahead of marketing and alert messages, so verification codes are never waiting behind a bulk send.
- Auto-routing — Set
channel: "auto"and senderZ delivers via iMessage when available, SMS when not. You write the code once, it works for everyone. - Template system — Create a reusable OTP template with dynamic variables for the code, expiry time, and app name. Update the copy once and it applies to every send.