otp.com vs Sinch Verification API

otp.com has no write-up on Specifiction yet; its figures are above.

Sinch Verification API provides multi-factor authentication and phone-number verification for app sign-up, login, and password resets. Developers can use one-time passwords, password-free verification, or other account checks through backend REST APIs and native Android and iOS SDKs. Verification methods include SMS, voice calls, flash calls, and data verification. Sinch describes multilingual service across devices and platforms, with fallback options for delivery, conversion, and price, supported by more than 600 direct tier-1 operator connections. Its Dashboard shows verification results and delivery and conversion metrics in real time. Named identity integrations include Okta and Auth0, while developer guides also cover ForgeRock and SAP. Data Verification requires mobile data to be enabled, and Sinch advises contacting an account manager to use it. For SDK requests from untrusted mobile devices, Sinch recommends Public Authentication and says verification callbacks should validate requests to help prevent fraud. The service has free access and trial credit through Sinch Build. Pay-as-you-go verification is billed per request; SMS pricing varies by country and operator, while flash calls have a fixed price per attempt.