OTP SMS Verification API

SpringEdge's OTP SMS Verification API lets you authenticate users by sending a one-time password to their mobile number via SMS. With an average delivery time of under 3 seconds, direct carrier connectivity across India and 85+ countries, and 99.9% platform uptime, SpringEdge is built for applications where speed and reliability are non-negotiable — from login authentication and user registration to payment confirmation and account recovery.

What Is OTP SMS Verification?

OTP (One-Time Password) SMS verification is a widely used method for confirming a user's identity by sending a unique, time-limited numeric code to their registered mobile number. The user enters this code in your application to complete authentication. It is one of the most effective forms of two-factor authentication (2FA) because it combines something the user knows (their account credentials) with something they have (their mobile phone).

OTP verification is mandated or recommended by the Reserve Bank of India (RBI) for online financial transactions, and is widely adopted across e-commerce, healthcare, logistics, and SaaS platforms for securing user accounts.

How OTP SMS Verification Works

The OTP verification flow with SpringEdge is straightforward:

  1. User action: A user registers, logs in, or initiates a transaction in your application.
  2. OTP generation: Your server generates a random numeric code (typically 4-6 digits) and stores it temporarily with an expiry time.
  3. API call: Your server sends an HTTP request to the SpringEdge SMS API with the user's mobile number and the OTP message.
  4. SMS delivery: SpringEdge routes the message through the fastest available carrier path and delivers the OTP to the user's phone within seconds.
  5. User verification: The user enters the OTP in your application. Your server validates it against the stored code and expiry time.
  6. Access granted: On successful match, the user is authenticated and can proceed.

Common Use Cases

User Registration & Signup

Verify new user mobile numbers during account creation to prevent fake signups, reduce spam accounts, and ensure a valid contact channel for future communication.

Login Authentication (2FA)

Add a second layer of security to user logins. Even if passwords are compromised, OTP verification prevents unauthorised access by requiring physical access to the registered phone.

Transaction Confirmation

Secure financial transactions, fund transfers, and high-value actions with OTP confirmation. Required by RBI for online payments in India and trusted by banks, fintech, and e-commerce platforms.

Password Reset & Account Recovery

Allow users to securely reset forgotten passwords by verifying their identity through an OTP sent to their registered mobile number, eliminating the risk of email-based phishing attacks.

Delivery & Logistics Confirmation

Confirm package delivery by sending an OTP to the recipient. The delivery agent enters the code to verify handover, reducing disputes and fraudulent delivery claims.

Healthcare & Appointment Verification

Authenticate patients during telemedicine consultations, prescription pickups, and appointment check-ins. Ensures compliance with data privacy regulations while securing sensitive health records.

Why Choose SpringEdge for OTP SMS

  • Sub-3-second delivery: Direct carrier routes and intelligent failover routing ensure OTPs arrive before your users lose patience.
  • 99.9% uptime SLA: Enterprise-grade infrastructure with redundant systems ensures your authentication flow never goes down.
  • DLT compliant: We handle entity registration, sender ID (header) management, and template approval as required by TRAI for Indian messaging.
  • Global reach: Send OTP SMS to mobile numbers in 85+ countries through our international carrier network.
  • Auto-retry & smart routing: If a carrier path fails, SpringEdge automatically reroutes through an alternate path — no intervention needed.
  • Real-time delivery reports: Get instant delivery status callbacks (DLR) via webhooks to track OTP delivery success rates.
  • High throughput: Handle thousands of OTP requests per second without throttling, suitable for flash sales, peak login hours, and large-scale campaigns.
  • Secure by design: HTTPS-only API endpoints, API key authentication, and IP whitelisting keep your OTP flow secure.

Quick Integration Guide

Getting started with SpringEdge OTP SMS takes just a few steps:

  1. Create a free account: Sign up for a SpringEdge developer account and receive test credits instantly.
  2. Get your API key: Log in to your dashboard and copy your unique API key from the settings page.
  3. Register DLT template (India): For Indian numbers, register your OTP message template on the DLT portal. SpringEdge assists with template approval — learn more about DLT.
  4. Integrate the API: Use our RESTful API with your preferred language. Below is a quick example using cURL:

cURL Example

curl https://web.springedge.com/api/web/send \
  -F apikey=YOUR_API_KEY \
  -F sender=YOURID \
  -F to=919XXXXXXXXX \
  -F message="Your OTP is 482910. Valid for 5 minutes. Do not share." \
  -F format=json

Replace YOUR_API_KEY with your actual API key, YOURID with your approved sender ID, and the phone number with the user's mobile number.

Our API supports cURL, PHP, Python, Java, Ruby, Node.js, Go, and C#/.NET. For complete code samples in all languages, visit the Developers API page.

Best Practices for OTP Implementation

  • Keep OTPs short-lived: Set an expiry of 5-10 minutes. Shorter windows reduce the risk of interception.
  • Use numeric codes only: 4-6 digit numeric OTPs are easier for users to enter on mobile keyboards and work with auto-fill on Android and iOS.
  • Rate limit OTP requests: Prevent abuse by limiting how many OTPs a single number can request within a time window (e.g., 3 per 10 minutes).
  • Never log OTPs: Avoid storing OTPs in application logs. Hash them in your database and compare against the hashed value.
  • Include clear messaging: Your SMS should state the OTP, its purpose, validity period, and a warning not to share it (e.g., "Your login OTP is 482910. Valid for 5 minutes. Do not share this code with anyone.").
  • Implement retry with backoff: If OTP delivery fails, retry with increasing intervals rather than flooding the carrier network.
  • Use DLR callbacks: Monitor delivery reports to detect and handle failed deliveries proactively — offer voice OTP as a fallback.

Frequently Asked Questions

What is OTP SMS verification?

OTP SMS verification is a security method where a one-time password (typically 4-6 digits) is sent via SMS to a user's mobile number. The user enters this code to prove they have access to the phone number, confirming their identity for login, registration, or transaction approval.

How fast does SpringEdge deliver OTP SMS?

SpringEdge delivers OTP SMS within 3 seconds on average through direct carrier connectivity and intelligent routing. Our platform maintains 99.9% uptime with automatic failover to ensure OTPs reach users instantly.

Which programming languages does the OTP SMS API support?

SpringEdge's OTP SMS API supports cURL, PHP, Python, Java, Ruby, Node.js, Go, C#/.NET, Android, and more. The RESTful API can be integrated with any platform that supports HTTP requests.

Is OTP SMS DLT compliant in India?

Yes. SpringEdge handles full DLT compliance for OTP messages in India, including entity registration, template approval, and header management as mandated by TRAI. All OTP templates are pre-approved for instant delivery.

Can I send OTP SMS internationally?

Yes. SpringEdge supports OTP SMS delivery to 85+ countries through our international carrier network. Delivery speeds and routes are optimised per country for the best possible experience.

What happens if OTP SMS delivery fails?

SpringEdge automatically retries through alternate carrier routes. You can also configure webhook callbacks to receive real-time delivery reports (DLR) and trigger fallback mechanisms such as voice OTP or email verification.