Voice OTP

What is Voice OTP?

Voice OTP is a verification method that delivers a one-time password through an automated phone call in which a text-to-speech voice reads the code aloud for the user to enter.

Voice OTP replaces the SMS delivery channel with an outbound voice call. When a user triggers verification, the platform dials their number and a TTS engine reads the numeric code aloud, usually twice; the user then types it into the app or website. Because no message is sent or stored, voice OTP removes the attack surface exploited by SIM swap harvesting, SS7 SMS rerouting, and SMS-reading malware — the code exists only inside a live, answered call. The method works on any device that can receive a call, including feature phones and landlines, with no app or data connection required. Example: a fintech platform sends withdrawal confirmations by voice OTP while keeping SMS for routine logins, so its highest-risk codes never touch the SMS channel. At BSG, voice OTP is delivered as One Voice Calls (OVC) with automatic SMS fallback through a single API.

For more on this, see BSG's OTP SMS vs. Flash Calls: Multi-Factor Authentication Solutions Compared.

Related terms

• OTP (One-Time PIN Code)
• Flash Call
• 2FA

Related BSG products

• 2FA/OTP Platform
• Number Verifier
• Bulk SMS