Login is the first interaction every user has with your product — and it's also the highest-frequency messaging event any SaaS platform sends. MetaReach's OTP API is built for exactly this: fast, reliable, and provisioned to scale with your user growth rather than becoming a bottleneck.
Core Capabilities
Trigger OTP with a single API call, verify with a second.
For login-critical OTP.
Use one or both, with automatic fallback options.
Different business customers on your platform can use independent sender IDs.
Built in to prevent OTP abuse.
MetaReach's OTP API lets SaaS platforms trigger login/signup OTP via a single REST call, with sub-5-second average delivery, SMS-and-WhatsApp fallback, multi-tenant sender-ID support, and built-in rate-limiting to prevent abuse.
Integration Pattern
A typical OTP login flow, end to end.
Integration Flow
Expiry, Resends & Abuse Controls
A login OTP flow has to work correctly not just on the happy path, but when a code expires, a user asks for another one, or someone tries to guess their way past verification. These are the details that separate a working demo from a production-ready login flow.
Codes expire after a short window rather than staying valid indefinitely; an expired code prompts a clean resend instead of a confusing silent failure.
Resend requests are throttled with a cooldown between attempts, so a genuine retry still works while repeated tapping can't be used to flood a number.
After a small number of incorrect code entries, that code is invalidated and a fresh one is required — closing off simple brute-force guessing against a live OTP.
SMS-first or WhatsApp-first ordering, with automatic fallback to the other channel if the first attempt doesn't deliver, so a single carrier hiccup doesn't block a login.
Delivery status for every OTP send is available via webhook in near real time, which is what makes automatic channel fallback possible in the first place — your app doesn't have to guess whether a message went through, it can react to an actual delivery event. Combined with rate-limiting on both the send and verify endpoints, this is the layer of the integration most teams underestimate when they first scope an OTP flow, and it's typically the difference between an implementation that works in testing and one that holds up against real-world abuse patterns after launch.
Go Further
Login verification is one piece of a SaaS platform's communication needs — these resources round out the rest.
In-app alerts and updates delivered via WhatsApp.
Explore WhatsApp NotificationsFull REST API docs, webhooks, and sandbox environment.
View Integration GuideResell this infrastructure under your own brand.
Explore White-Label OptionsSee how SaaS platforms and ERP providers use this infrastructure.
View Use CasesMetaReach's general-purpose OTP and transactional SMS pillar.
View OTP & SMS ServicesPassword resets, receipts, and system alerts.
Explore Transactional EmailVoice-based support routing and escalation.
Explore IVR for Customer SupportNeed the rest of the SaaS & ERP communication stack? See the SaaS & ERP Messaging Solutions pillar for WhatsApp, SMS, Email, IVR, and API integration in one place.
Common Questions
Yes — the infrastructure is provisioned for burst capacity, not just average-day volume.
Yes, for production SMS OTP in India. MetaReach handles sender-ID registration as part of onboarding. See DLT Registration Support.
Yes — per-tenant configuration is supported.
Yes — see our Messaging API Integration Guide for sandbox access details.
Expiry windows are configurable to match your security requirements, with a short default window common for login OTP. Exact defaults are confirmed during onboarding.
Resend requests are rate-limited with a cooldown period between attempts, which prevents abuse of the resend flow while still allowing genuine retries when a message is delayed.
Yes — SMS-to-WhatsApp (or the reverse) fallback ordering can be configured, so a failed delivery on one channel doesn't block a user from completing login.
From startups to enterprises — brands that grow with MetaReach
