Every failed verification code is a lost signup, a failed login or an abandoned payment. The channel you deliver OTPs on is therefore not a technical detail — it is a conversion decision. Here is how WhatsApp and SMS compare on the four dimensions that matter.

Delivery and speed

SMS delivery depends on carrier routes that vary by operator and time of day; codes can arrive late or never, and you rarely learn which. WhatsApp OTPs travel over the internet with delivery and read receipts — you know within seconds whether the code reached the device, and in markets like Morocco where WhatsApp is always open, codes are typically seen faster.

Security

SMS is vulnerable to SIM-swap attacks and SS7 interception — real risks for anything touching money. WhatsApp messages are end-to-end encrypted and tied to the app's own device registration, which raises the bar considerably. Meta's dedicated authentication template type also enforces a strict format with no links, reducing phishing lookalikes.

Cost per verification

Authentication conversations on WhatsApp are priced for high-volume use and in many markets undercut SMS — sometimes substantially once failed SMS deliveries you still pay for are counted. Model it on your own volumes: the honest metric is cost per successful verification, not per message sent.

The right architecture: WhatsApp-first with SMS fallback

• Send the OTP on WhatsApp first for users whose numbers are registered there.
• If undelivered within a short window — say ten seconds — fall back to SMS automatically.
• Log both legs so you can watch the split and the savings.

This hybrid keeps conversion high for the WhatsApp majority without abandoning feature-phone users.

SalesRep supports authentication templates and messaging APIs alongside your customer conversations, so verification and support finally live on the same number. Talk to us about OTP volumes, or start the free 21-day trial.