WhatsApp OTP vs SMS OTP in India: cost, delivery, and what actually converts

Indian SMS OTP delivery rates hover between 70-85% depending on operator and DND filtering. WhatsApp authentication messages — the dedicated Meta template category — deliver at 95%+ because they bypass DLT registration entirely and land in the app your users actually open 30 times a day.

The cost math

WhatsApp authentication messages cost ~₹0.115-0.35 per send at Meta's India rates. SMS via 2Factor or MSG91 runs ₹0.18-0.40. Voice OTP — the last resort — is ₹0.80+. On pure cost WhatsApp already wins.

The conversion math

A code that never arrives costs you a signup. At 15% SMS non-delivery, every 10k logins lose 1,500 users at the gate. That's the real spend — not the ₹0.20.

The smart cascade

The right architecture is channel-cascading: WhatsApp first (cheapest + highest delivery), SMS fallback for non-WhatsApp users, voice for the long tail. NexAuth does this automatically per identifier — you configure the route order once.

When SMS still wins

• Feature phones / no-WhatsApp demographics (rural, elderly)
• iOS users without WhatsApp installed
• Compliance contexts requiring telco-grade delivery evidence

Design for the cascade, measure per-channel delivery, and let the router optimize — not your code.