BulkSMS vs StartMessaging for OTP in India

“Bulk SMS” and “OTP API” are often used interchangeably in the Indian SMS market, but they are different products solving different problems. This guide explains why a generic bulk-SMS provider is rarely the right fit for OTP, and what OTP-focused APIs add.

Bulk SMS vs OTP API: A Category Difference

• Bulk SMS — designed for marketing blasts and high- volume notifications. Optimised for throughput, not latency.
• OTP API — designed for one-message-at-a-time authentication. Optimised for sub-5s delivery, hashed storage and attempt limits.

Why Generic Bulk-SMS Underperforms on OTP

• Higher latency on bulk routes.
• No code generation, hashing or verification API.
• No attempt limits or expiry baked in.
• No idempotency keys.
• Per-operator scrubbing tuned for promotional, not transactional.

Features OTP-Focused APIs Add

• Two-call API: /otp/send, /otp/verify.
• Plaintext code never on customer servers — only requestId.
• bcrypt-hashed storage on the provider side.
• Per-request attempt counters and expiry.
• Idempotency for retry-safe sends.
• Voice fallback on a shared requestId.

When Bulk SMS Still Wins

• Marketing campaigns.
• Order-status SMS at low priority.
• Newsletter blasts.
• Already-have-OTP-built workloads with stable in-house code.

FAQ

For OTP and authentication, use a dedicated OTP API. StartMessaging is built for exactly this — and is DLT-free, so you can also handle bulk OTP bursts on the same key.