SecondFactor is an OTP API for vibe-coders and product teams that delivers and verifies OTPs over SMS, WhatsApp, RCS, and Viber through a single integration. It's built for two-factor authentication (2FA), and OTP verification. It fits fintech, tech-enabled marketplaces, and international platforms that send OTPs to users in more than one country. The cost of OTP Delivery rises as you add countries, channels, and destinations. Even with these complications, the OTP often fails to arrive, causing valuable customers to abandon sign-up, or a purchase. This is where SecondFactor comes in: the Intelligence Engine identifies the destination country and operator, checks which channels are available, and uses automatic routing to send the OTP over the lowest-cost eligible channel. If the delivery isn’t confirmed within 8 seconds, automatic fallback moves to the next eligible channel. Your backend doesn't generate, store, or check the code itself. Instead, SecondFactor generates the code, picks the optimal channel, delivers the OTP and verifies it. The SecondFactor dashboard consists of every OTP's destination, channel, delivery status, and cost, in one place across all channels. With multiple SDKs alongside LLM-friendly API, integration with AI agents like Claude, Copilot, Cursor, etc. becomes seamless. If you are moving from another OTP provider, you keep a simple send-and-verify integration instead of rebuilding your verification workflow. With credible coverage of 130+ destinations, including the USA, UK, Germany, France, India, Mexico, Peru, Brazil, UAE, and many more, sending international OTPs is efficient, and reliable. Our clients – Rara Global Ventures, Lambda Payments, Janaki Technology, and Eventra – have experienced and appreciated the reliability of our service. Get started with SecondFactor and get your $5 in free credits. Test real OTP in the Playground.