OTP (One-Time Password) verification confirms that a user owns a phone number by sending a single-use code via SMS. The user enters the code in your app to prove their identity — a standard method for login, signup, two-factor authentication, and fraud prevention.
How does SMS OTP work?
- User enters their phone number in your app
- Your backend calls an OTP API to send a code via SMS
- User receives the code and enters it in your UI
- Your backend validates the code and returns a signed verification token
Why use OTP verification?
Phone numbers are harder to fake at scale than email addresses. OTP verification reduces fake accounts, account takeover, and payment fraud — especially in markets where mobile-first users dominate.
| Use case | Benefit |
|---|---|
| Login / signup | Confirms real users before account creation |
| Payments | Reduces chargebacks and stolen-card abuse |
| Password reset | Secure recovery without email dependency |
| High-risk actions | Step-up verification for withdrawals or profile changes |
OTP vs other verification methods
Email verification is cheap but easy to automate. Authenticator apps are secure but add friction. SMS OTP balances security and conversion — users already expect a text message when signing up or logging in.
FAQ
How long is an OTP code valid?
Typically 5 minutes. DoneOTP defaults to 300 seconds — configurable per project.
Is SMS OTP secure enough?
For most consumer apps, yes — especially combined with rate limiting and fraud detection. High-security use cases may add app-based 2FA as a second factor.