What is OTP API?

A programmatic interface that allows applications to generate and deliver one-time passwords via SMS for user authentication and identity verification.

An OTP API is a specialized SMS API endpoint optimized for the unique requirements of one-time password delivery. Unlike general-purpose SMS APIs, OTP APIs are designed for high-speed, high-reliability delivery with features tailored to authentication use cases—including built-in OTP generation or support for custom OTP strings, configurable expiry times, resend throttling, DND bypass for transactional routing, and intelligent fallback to Voice OTP on delivery failure. The API typically accepts the recipient's mobile number and OTP content, and returns a message ID and delivery status. Developers integrate OTP APIs into login screens, payment confirmation flows, password reset pages, and account verification steps. BhashSMS's OTP API supports multiple concurrent sessions and provides sub-second delivery confirmation.

Frequently Asked Questions

Compliance

Does the OTP API generate the OTP or do I need to generate it myself?

Most OTP APIs accept the OTP string you generate in your application, giving you control over length, format, and complexity. Some platforms also offer OTP generation as an optional service. BhashSMS's API accepts both modes—you can pass your own OTP or request server-side generation.

Speed

What delivery rate can I expect from an OTP API?

High-quality OTP APIs achieve delivery rates of 98–99.5% through multi-operator routing, intelligent failover, and priority lanes. The remaining failures are typically due to invalid numbers, switched-off devices, or full inboxes. Implementing Voice OTP fallback can push effective delivery rates even higher.

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Related Terms

Promotional SMS OTP DND Bulk SMS Sender ID SMS Gateway Priority Route TRAI 2FA

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