The unglamorous API your login flow lives or dies by
One-time passwords look trivial until you build them at scale, and then every detail bites. The code has to arrive in seconds, because an OTP that shows up after the timeout is a failed login and a frustrated user. It has to arrive reliably, because a delivery failure locks a legitimate customer out of their own account. It has to be secure, because OTP flows are a target. And ideally it works across channels, because SMS isn't always the best or available route. Getting this right is more work than teams expect — which is exactly why an API that has solved it is worth using.
Our 2FA/OTP API is built for this specific job — fast, reliable, multi-channel OTP delivery — on the same infrastructure as our Messaging Hub platform. It handles the delivery reliability so your application can just request a code and trust it arrives.
What the API does
Multi-channel OTP
Deliver one-time passwords over SMS, WhatsApp or email — choose the right channel, or let fallback handle it automatically.
Speed-optimised routing
OTP traffic routed for the lowest reliable latency, because a slow code is a failed login.
Automatic fallback
If the primary channel fails or lags, the code is re-sent via an alternative — so delivery failures don't become lockouts.
Secure by design
Sensible code generation, expiry and verification handling, so the OTP flow itself isn't the weak link.
Delivery analytics
Visibility into delivery and success rates, so you can see and fix problems rather than guess at them.
Clean developer API
A simple, well-documented API — request a code, verify a code — that's a quick integration, not a project.
Fallback routing: because a failed OTP is a locked-out customer
The worst OTP failure isn't slowness — it's a code that never arrives, leaving a legitimate customer unable to log into their own account. Single-channel OTP has a hard ceiling: if SMS delivery to a particular number fails, the login fails, and there's nothing more to try. Our API handles this with automatic fallback: if the primary channel doesn't deliver, the code is re-sent through an alternative channel, turning what would have been a lockout into a successful authentication by another route. For a business, that's the difference between a smooth login and a support ticket — or a lost customer who couldn't get in.
Security in the OTP flow itself
OTP exists to add security, so the flow itself must not become a vulnerability. That means sound practices around code generation (unpredictable codes), expiry (short-lived, single-use), rate limiting (to resist brute-force and abuse), and verification handling — details that are easy to get subtly wrong when rolling your own. Our API handles these correctly by design, so you get the security benefit OTP is meant to provide rather than a flawed implementation that merely looks secure. As a security firm, we build the authentication flow to the standard we'd want to find when testing someone else's.
Integration in an afternoon, not a sprint
OTP is something developers integrate under deadline pressure, so the API is deliberately simple: two core operations — request a code to a destination, and verify a code the user entered — with clear documentation and predictable responses. Adding two-factor authentication to a login flow, verifying a phone number at signup, or confirming a transaction becomes a quick, well-understood integration rather than a delivery-reliability project you didn't budget for. Where you want it wired deeply into a custom flow, our software team knows the API intimately.
Who it's for
- Developers adding 2FA or phone/email verification and wanting reliable delivery without building it themselves.
- Applications with logins where authentication reliability directly affects whether users can get in.
- Fintech and sensitive services where strong, dependable verification is essential.
- Any product where a delivery failure means a locked-out customer and a support ticket.
Frequently Asked Questions
Why not just send OTPs with a normal SMS API?
You can, but OTP has specific demands a general SMS send doesn't address: latency (a slow code fails the login), reliability (a failed delivery locks users out), fallback across channels, and secure code handling. Our OTP API is built for exactly those demands, so you don't rediscover them the hard way in production. A plain SMS send leaves the reliability and security engineering to you.
What channels can OTP be delivered over?
SMS, WhatsApp and email. You can choose the channel, or use automatic fallback so that if the primary channel fails, the code goes out via an alternative. Multi-channel matters because no single channel is universally best or always available — fallback is what turns a would-be delivery failure into a successful login.
How does fallback routing work?
If the primary channel doesn't deliver the code (failure or excessive delay), the API automatically re-sends via an alternative channel. This directly prevents the worst OTP outcome — a legitimate user locked out because their code never arrived. Single-channel OTP has no answer when its one channel fails; fallback gives the delivery a second path.
How fast do OTP codes arrive?
OTP traffic is routed for the lowest reliable latency, so codes typically arrive within seconds under normal conditions. Speed is prioritised because a one-time password that arrives after its expiry window is worse than useless — it just fails the login. Fast, reliable delivery is the core promise of the API.
Is the OTP flow itself secure?
Yes — the API handles code generation, short single-use expiry, rate limiting against brute-force, and verification correctly by design. These are details that are easy to get subtly wrong when building your own, turning a security feature into a vulnerability. Built by a security firm, the flow is designed to actually deliver the protection OTP is meant to provide.
How hard is it to integrate?
Deliberately easy — two core operations (request a code, verify a code) with clear docs and predictable responses. Adding 2FA, phone/email verification or transaction confirmation is typically an afternoon's integration, not a multi-day project. The whole point is that we've absorbed the hard delivery-reliability engineering so you don't have to.
Can it handle transactional messages too, not just OTP?
Yes — it's built on our broader Messaging Hub platform, so it extends naturally to transactional messaging beyond OTP. If you need general SMS/WhatsApp sending as well, Messaging Hub is the fuller platform; the OTP API is the focused, optimised entry point when authentication is your primary need.
WhatsApp is a trademark of Meta Platforms, Inc. Delivery speed and reliability depend on carrier routing and recipient availability. Xcodefix Global builds and operates this API.