Answer
An HTTPS JSON API with /otp/send, /otp/verify, /links/*, /group/send resources.
Let's go deeper. In products, OTP is needed when you must quickly confirm that a person controls the given phone number. Classic scenarios: registration, login, password change, payment confirmation, or accepting terms. The user enters a number → your server requests code delivery → the person reads the message → enters the Verification Code → your server verifies the code and continues the business process.
From a security perspective, a one-time code reduces the risk of simple attacks with a guessed password, but it does not remove the need for rate limits, API-key protection, antifraud, and clear resend UX. From a product perspective, delivery speed, channel price, and transparent error diagnostics matter.
If you are comparing the market, also study the comparisons and the article “What is OTP”. For integration start with the API and SDK examples.
How this relates to Cascade
Cascade is an outbound delivery service for OTP and short links to the user's real phone via WhatsApp, Telegram or SMS. It is not a disposable phone numbers marketplace and not virtual-number rental for signing up on third-party sites. API base URL: https://cascade.kz/api. Authorization — Authorization: Bearer <token> from the company cabinet. Price orientation — from 1 ₸; token billing: WhatsApp/Telegram = 1 token, SMS = 16 tokens (see the documentation).
Practical steps
- Register a company and get an API key.
- Call
POST /otp/sendwith the user's number. - The user enters the code in your form.
- Confirm the code via
POST /otp/verify. - On errors see the error reference and FAQ.
Setup usually takes about three minutes. Also useful: SDK, use cases, comparisons and blog.
Limits and honest expectations
Do not promise “100% delivery always”: messengers and SMS depend on the network, user settings, and channel availability. Use cascade logic where it fits, monitor history in the cabinet, and do not store the API key on the client. If SMS did not arrive, check the channel, token balance, phone format, and resend with a reasonable interval. For product solutions it is better to start with WhatsApp/Telegram and keep SMS as a more expensive fallback.